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# Know what is growing.

An illustrated reference to garden weeds and wild plants found in Colorado. Compare what plants look like and read sourced information about their effects on people, animals and local habitats. Open a plant card to see its photographs, descriptions and source links.

154 plants in this view; 154 profiles and 462 photographs in the guide.

[Biggest concerns](https://denson.github.io/colorado-weed-field-guide/biggest-concerns/) · [Coverage: all 82 state-list entries](https://denson.github.io/colorado-weed-field-guide/coverage/) · [Exposure and safety guide](https://denson.github.io/colorado-weed-field-guide/safety/) · [Learn to use this guide](https://denson.github.io/colorado-weed-field-guide/companion/)

## Native volunteers

- [Black greasewood](https://denson.github.io/colorado-weed-field-guide/plants/black-greasewood/) — *Sarcobatus vermiculatus*. **Oxalate poisoning can be fatal to livestock**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/black-greasewood/index.md).
  ![Low, spreading greasewood shrub with dense green foliage in open dry ground.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/black-greasewood.webp) Photo: John Gaskin; CC0 1.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/black-greasewood/).
- [Broom snakeweed](https://denson.github.io/colorado-weed-field-guide/plants/broom-snakeweed/) — *Gutierrezia sarothrae*. **Livestock poisoning and abortion risk when heavily eaten**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/broom-snakeweed/index.md).
  ![Small branching broom snakeweed plant with yellow flower clusters above a woody base on rocky ground.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/broom-snakeweed.webp) Photo: CK2AZ; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/broom-snakeweed/).
- [Buffalobur](https://denson.github.io/colorado-weed-field-guide/plants/buffalobur/) — *Solanum rostratum*. **Sharp spines; toxic to livestock**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/buffalobur/index.md).
  ![Solanum rostratum: Deeply lobed leaves and prickly stems, with a yellow flower visible at the edge.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/buffalobur.webp) Photo: Juan Carlos Fonseca Mata; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/buffalobur/).
- [Canada goldenrod](https://denson.github.io/colorado-weed-field-guide/plants/canada-goldenrod/) — *Solidago canadensis*. **Spreads by roots and seed**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/canada-goldenrod/index.md).
  ![Solidago canadensis: A goldenrod stem with a branching yellow flower plume and narrow, alternate toothed leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/canada-goldenrod.webp) Photo: Étienne Lacroix-Carignan; CC0 1.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/canada-goldenrod/).
- [Catchweed bedstraw](https://denson.github.io/colorado-weed-field-guide/plants/catchweed-bedstraw/) — *Galium aparine*. **Hooked hairs and burrs cling to fur and clothing**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/catchweed-bedstraw/index.md).
  ![Galium aparine: Small white flowers and rounded young fruits at the tip of a prickly leafy shoot.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/catchweed-bedstraw.webp) Photo: Krzysztof Ziarnek, Kenraiz; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/catchweed-bedstraw/).
- [Common blue violet](https://denson.github.io/colorado-weed-field-guide/plants/common-blue-violet/) — *Viola sororia*. **A native volunteer; identify the species before removing**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-blue-violet/index.md).
  ![Common blue violet: a single violet flower with purple-and-pale petals and darker veins leading toward its center.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-blue-violet.webp) Photo: James Steakley; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-blue-violet/).
- [Common ragweed](https://denson.github.io/colorado-weed-field-guide/plants/common-ragweed/) — *Ambrosia artemisiifolia*. **Pollen allergy; skin irritation**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-ragweed/index.md).
  ![Ambrosia artemisiifolia: A low stand of common ragweed flowering along the edge of a paved path, with other vegetation nearby.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-ragweed.webp) Photo: Ayotte, Gilles, 1948-; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-ragweed/).
- [Common sunflower](https://denson.github.io/colorado-weed-field-guide/plants/common-sunflower/) — *Helianthus annuus*. **Listed non-toxic to dogs & cats**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-sunflower/index.md).
  ![Helianthus annuus: Front view of a sunflower head, showing yellow ray florets surrounding the darker central disk.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-sunflower.webp) Photo: Michelle W. （鍾偉瑋）; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-sunflower/).
- [Curlycup gumweed](https://denson.github.io/colorado-weed-field-guide/plants/curlycup-gumweed/) — *Grindelia squarrosa*. **Sticky resin and conditional selenium concern**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/curlycup-gumweed/index.md).
  ![Rounded, densely branching curlycup gumweed plant covered with yellow flower heads.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/curlycup-gumweed.webp) Photo: Jesse Grove; CC0 1.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/curlycup-gumweed/).
- [Foxtail barley](https://denson.github.io/colorado-weed-field-guide/plants/foxtail-barley/) — *Hordeum jubatum*. **Barbed seed awns injure animals**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/foxtail-barley/index.md).
  ![Hordeum jubatum: A tuft of foxtail barley with slender leaves and pale pink, long-awned heads.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/foxtail-barley.webp) Photo: Diego Delso; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/foxtail-barley/).
- [Giant ragweed](https://denson.github.io/colorado-weed-field-guide/plants/giant-ragweed/) — *Ambrosia trifida*. **Allergenic pollen and strong competition in disturbed ground**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/giant-ragweed/index.md).
  ![Ambrosia trifida: An upright giant ragweed plant beside a fence, with large three- to five-lobed leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/giant-ragweed.webp) Photo: GTBacchus; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/giant-ragweed/).
- [Golden banner](https://denson.github.io/colorado-weed-field-guide/plants/golden-banner/) — *Thermopsis divaricarpa*. **May poison livestock**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/golden-banner/index.md).
  ![Thermopsis divaricarpa: An upright shoot with yellow flower buds and emerging flowers above leafy nodes and broad stipules.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/golden-banner.webp) Photo: Laura J. Costello; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/golden-banner/).
- [Hemp dogbane](https://denson.github.io/colorado-weed-field-guide/plants/hemp-dogbane/) — *Apocynum cannabinum*. **Cardiac-glycoside poisoning hazard for people and animals**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/hemp-dogbane/index.md).
  ![Apocynum cannabinum: A dense leafy flowering stand beside a cultivated field.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/hemp-dogbane.webp) Photo: Ayotte, Gilles, 1948-; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/hemp-dogbane/).
- [Horseweed](https://denson.github.io/colorado-weed-field-guide/plants/horseweed/) — *Erigeron canadensis*. **Fast windborne spread; some populations resist herbicides**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/horseweed/index.md).
  ![Erigeron canadensis: A tall upright stem topped by a broad, finely branched pale mature head cluster.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/horseweed.webp) Photo: Enrico Blasutto; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/horseweed/).
- [Low larkspur](https://denson.github.io/colorado-weed-field-guide/plants/low-larkspur/) — *Delphinium nuttallianum*. **Serious livestock and pet poisoning hazard**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/low-larkspur/index.md).
  ![Delphinium nuttallianum: A patch of low blue-flowered larkspur growing among stones and dry leaf litter.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/low-larkspur.webp) Photo: NPS; Public domain. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/low-larkspur/).
- [Meadow death camas](https://denson.github.io/colorado-weed-field-guide/plants/meadow-death-camas/) — *Toxicoscordion venenosum*. **Potentially fatal ingestion; onion-like bulbs**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/meadow-death-camas/index.md).
  ![Toxicoscordion venenosum: An upright cluster of small pale flowers above a basal group of narrow, strap-shaped leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/meadow-death-camas.webp) Photo: NPS Photo; Public domain. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/meadow-death-camas/).
- [Netseed lambsquarters](https://denson.github.io/colorado-weed-field-guide/plants/netseed-lambsquarters/) — *Chenopodium berlandieri*. **A fast-growing volunteer; pet toxicity remains unresolved**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/netseed-lambsquarters/index.md).
  ![Pitseed goosefoot: a small upright leafy goosefoot plant growing among stones in open ground.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/netseed-lambsquarters.webp) Photo: Matt Lavin; CC BY-SA 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/netseed-lambsquarters/).
- [Prairie sage](https://denson.github.io/colorado-weed-field-guide/plants/prairie-sage/) — *Artemisia ludoviciana*. **Spreading roots; pet evidence gap**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/prairie-sage/index.md).
  ![Artemisia ludoviciana: Dense, silvery foliage with narrow leaves, some divided into slender lobes.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/prairie-sage.webp) Photo: Matt Lavin from Bozeman, Montana, USA; CC BY-SA 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/prairie-sage/).
- [Showy milkweed](https://denson.github.io/colorado-weed-field-guide/plants/showy-milkweed/) — *Asclepias speciosa*. **Toxic if eaten**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/showy-milkweed/index.md).
  ![Asclepias speciosa: Close view of pale pink showy milkweed flowers, with long pointed hoods above reflexed petals.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/showy-milkweed.webp) Photo: Andrey Zharkikh; CC BY 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/showy-milkweed/).
- [Silverleaf nightshade](https://denson.github.io/colorado-weed-field-guide/plants/silverleaf-nightshade/) — *Solanum elaeagnifolium*. **Toxic leaves and berries; persistent spreading roots**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/silverleaf-nightshade/index.md).
  ![Upright silverleaf nightshade stem with gray-green leaves and purple flowers in a grassy field.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/silverleaf-nightshade.webp) Photo: Sam Kieschnick; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/silverleaf-nightshade/).
- [Snow-on-the-mountain](https://denson.github.io/colorado-weed-field-guide/plants/snow-on-the-mountain/) — *Euphorbia marginata*. **Latex can damage skin and eyes; toxic if eaten**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/snow-on-the-mountain/index.md).
  ![Tall, branching snow-on-the-mountain plant with green lower leaves and white-edged upper foliage.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/snow-on-the-mountain.webp) Photo: Mark G; CC0 1.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/snow-on-the-mountain/).
- [Spotted spurge](https://denson.github.io/colorado-weed-field-guide/plants/spotted-spurge/) — *Euphorbia maculata*. **Milky sap can injure skin and eyes; keep pets from chewing**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/spotted-spurge/index.md).
  ![Spotted spurge: low radiating reddish stems and small opposite leaves form a mat on stony ground.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/spotted-spurge.webp) Photo: Stefan.lefnaer; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/spotted-spurge/).
- [Stinging nettle](https://denson.github.io/colorado-weed-field-guide/plants/stinging-nettle/) — *Urtica dioica*. **Stinging hairs; this profile covers a taxonomic complex**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/stinging-nettle/index.md).
  ![Urtica dioica: An upright nettle stem bearing toothed opposite leaves and slender branching flower clusters.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/stinging-nettle.webp) Photo: Przykuta; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/stinging-nettle/).
- [Tall larkspur](https://denson.github.io/colorado-weed-field-guide/plants/tall-larkspur/) — *Delphinium barbeyi*. **Serious livestock and pet poisoning hazard**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/tall-larkspur/index.md).
  ![Delphinium barbeyi: A blue-flowered larkspur stem with several spurred flowers and divided stem leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/tall-larkspur.webp) Photo: Ms. Sticky; CC BY 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/tall-larkspur/).
- [Western poison ivy](https://denson.github.io/colorado-weed-field-guide/plants/western-poison-ivy/) — *Toxicodendron rydbergii*. **Skin-rash oil can travel on pet fur**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/western-poison-ivy/index.md).
  ![Toxicodendron rydbergii: Dense cluster of pale whitish berries among dry leaves and twigs.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/western-poison-ivy.webp) Photo: Andrey Zharkikh from Salt Lake City, USA; CC BY 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/western-poison-ivy/).
- [Western ragweed](https://denson.github.io/colorado-weed-field-guide/plants/western-ragweed/) — *Ambrosia psilostachya*. **A persistent perennial ragweed; allergy detail still under review**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/western-ragweed/index.md).
  ![Upright western ragweed stems with divided green leaves and elongated terminal flower spikes.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/western-ragweed.webp) Photo: Zihao Wang; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/western-ragweed/).
- [Western water hemlock](https://denson.github.io/colorado-weed-field-guide/plants/western-water-hemlock/) — *Cicuta douglasii*. **Potentially fatal poisoning; wetland look-alike danger**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/western-water-hemlock/index.md).
  ![Cicuta douglasii: Upright leafy stems with pinnately divided, sharply toothed leaflets.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/western-water-hemlock.webp) Photo: Lee Cain; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/western-water-hemlock/).
- [Western whorled milkweed](https://denson.github.io/colorado-weed-field-guide/plants/western-whorled-milkweed/) — *Asclepias subverticillata*. **High livestock toxicity**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/western-whorled-milkweed/index.md).
  ![Asclepias subverticillata: Several slender flowering stems with small white umbels and very narrow leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/western-whorled-milkweed.webp) Photo: Patrick Alexander from Las Cruces, NM; CC0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/western-whorled-milkweed/).
- [White locoweed](https://denson.github.io/colorado-weed-field-guide/plants/white-locoweed/) — *Oxytropis sericea*. **Toxic to livestock**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/white-locoweed/index.md).
  ![Oxytropis sericea: Dry tan pods clustered along a stalk, some split open near their tips.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/white-locoweed.webp) Photo: Matt Lavin from Bozeman, Montana, USA; CC BY-SA 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/white-locoweed/).

## Xeriscape spreaders

- [Big sagebrush](https://denson.github.io/colorado-weed-field-guide/plants/big-sagebrush/) — *Artemisia tridentata*. **Valuable native habitat; subspecies and pet evidence need care**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/big-sagebrush/index.md).
  ![Mountain big sagebrush (Artemisia tridentata subsp. vaseyana) shrub with upright reproductive shoots beside a mountain pond.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/big-sagebrush.webp) Photo: Matt Lavin; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/big-sagebrush/).
- [Blanketflower](https://denson.github.io/colorado-weed-field-guide/plants/blanketflower/) — *Gaillardia aristata*. **Contact dermatitis possible**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/blanketflower/index.md).
  ![Open yellow-rayed blanketflower heads with orange-yellow central disks and a reddish inner ring.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/blanketflower.webp) Photo: NPS / Jacob W. Frank; Public domain. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/blanketflower/).
- [Catmint](https://denson.github.io/colorado-weed-field-guide/plants/catmint/) — *Nepeta × faassenii*. **Spreading clumps; pet evidence gap**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/catmint/index.md).
  ![Macro view of violet-blue, two-lipped flowers with darker spotting and hairy calyces.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/catmint.webp) Photo: Didier Descouens; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/catmint/).
- [Common yarrow](https://denson.github.io/colorado-weed-field-guide/plants/common-yarrow/) — *Achillea millefolium*. **Toxic to pets · Skin irritation**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-yarrow/index.md).
  ![White flower-head cluster viewed from above, with individual ray and disk florets visible.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-yarrow.webp) Photo: Petar Milošević; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-yarrow/).
- [Fernleaf yarrow](https://denson.github.io/colorado-weed-field-guide/plants/fernleaf-yarrow/) — *Achillea filipendulina*. **Spreads; pet toxicity unresolved**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/fernleaf-yarrow/index.md).
  ![Macro view of a domed-to-flat cluster of small golden-yellow flower heads.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/fernleaf-yarrow.webp) Photo: Yerpo; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/fernleaf-yarrow/).
- [Fringed sage](https://denson.github.io/colorado-weed-field-guide/plants/fringed-sage/) — *Artemisia frigida*. **Spreading growth; pet evidence gap**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/fringed-sage/index.md).
  ![Low basal shoots with compact clusters of finely divided silvery-green leaves among dry vegetation.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/fringed-sage.webp) Photo: Matt Lavin  from Bozeman, Montana, USA; CC BY-SA 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/fringed-sage/).
- [Lamb’s-ear](https://denson.github.io/colorado-weed-field-guide/plants/lambs-ear/) — *Stachys byzantina*. **Can spread; pet evidence gap**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/lambs-ear/index.md).
  ![Magnified lamb's-ear leaf tip densely covered in silvery hairs, with a 10 mm scale.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/lambs-ear.webp) Photo: Stefan.lefnaer; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/lambs-ear/).
- [Lewis blue flax](https://denson.github.io/colorado-weed-field-guide/plants/lewis-blue-flax/) — *Linum lewisii*. **Ingestion and contact concerns**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/lewis-blue-flax/index.md).
  ![Close view of slender narrow leaves along a green flax stem.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/lewis-blue-flax.webp) Photo: Walter Siegmund   (talk); CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/lewis-blue-flax/).
- [Plains pricklypear](https://denson.github.io/colorado-weed-field-guide/plants/plains-pricklypear/) — *Opuntia polyacantha*. **Sharp spines around paws, mouths and eyes**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/plains-pricklypear/index.md).
  ![Low cluster of plains pricklypear pads covered with long pale spines on dry ground.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/plains-pricklypear.webp) Photo: eigenmotion; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/plains-pricklypear/).
- [Red valerian](https://denson.github.io/colorado-weed-field-guide/plants/red-valerian/) — *Centranthus ruber*. **Self-seeds beyond garden beds**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/red-valerian/index.md).
  ![Upright stem with opposite smooth leaves and several pink-red flower clusters on a rocky slope.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/red-valerian.webp) Photo: Robert Flogaus-Faust; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/red-valerian/).
- [Rubber rabbitbrush](https://denson.github.io/colorado-weed-field-guide/plants/rubber-rabbitbrush/) — *Ericameria nauseosa*. **A native low-water shrub that can spread readily**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/rubber-rabbitbrush/index.md).
  ![Rubber rabbitbrush shrub with yellow flowering tips and pale branching stems in grassland.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/rubber-rabbitbrush.webp) Photo: Ian Adams; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/rubber-rabbitbrush/).
- [Russian sage](https://denson.github.io/colorado-weed-field-guide/plants/russian-sage/) — *Salvia yangii*. **Spreads by suckers; pet evidence unresolved**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/russian-sage/index.md).
  ![Salvia yangii: Gray-green deeply divided leaves arranged in opposite pairs on a pale stem.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/russian-sage.webp) Photo: Doronenko; CC BY 2.5. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/russian-sage/).
- [Snow-in-summer](https://denson.github.io/colorado-weed-field-guide/plants/snow-in-summer/) — *Cerastium tomentosum*. **Spreading habit · Safety gap**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/snow-in-summer/index.md).
  ![Several white flowers with deeply notched petals above gray-green foliage.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/snow-in-summer.webp) Photo: Salicyna; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/snow-in-summer/).
- [Soapweed yucca](https://denson.github.io/colorado-weed-field-guide/plants/soapweed-yucca/) — *Yucca glauca*. **Sharp leaves · Toxic to pets**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/soapweed-yucca/index.md).
  ![Vertical stalk with pendulous cream-colored bell-shaped flowers and unopened buds.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/soapweed-yucca.webp) Photo: Alvesgaspar; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/soapweed-yucca/).

## Invasive & common weeds

- [Absinth wormwood](https://denson.github.io/colorado-weed-field-guide/plants/absinth-wormwood/) — *Artemisia absinthium*. **Ingestion toxicity and skin irritation**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/absinth-wormwood/index.md).
  ![Dense young growth with deeply divided gray-green leaves, viewed from above.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/absinth-wormwood.webp) Photo: Agnieszka Kwiecień, Nova; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/absinth-wormwood/).
- [African rue](https://denson.github.io/colorado-weed-field-guide/plants/african-rue/) — *Peganum harmala*. **Highly poisonous if eaten; deep-rooted invader**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/african-rue/index.md).
  ![Peganum harmala: A partly open white flower above narrow, deeply divided leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/african-rue.webp) Photo: Alex Abair; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/african-rue/).
- [Annual sowthistle](https://denson.github.io/colorado-weed-field-guide/plants/annual-sowthistle/) — *Sonchus oleraceus*. **Windborne seed and crop-pest hosting**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/annual-sowthistle/index.md).
  ![Sonchus oleraceus: Close view of a pale yellow head composed of many narrow strap-shaped florets.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/annual-sowthistle.webp) Photo: Miwasatoshi; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/annual-sowthistle/).
- [Bittersweet nightshade](https://denson.github.io/colorado-weed-field-guide/plants/bittersweet-nightshade/) — *Solanum dulcamara*. **Poisonous berries and foliage**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/bittersweet-nightshade/index.md).
  ![Solanum dulcamara: Dense tangle of leafy scrambling stems with pointed green leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/bittersweet-nightshade.webp) Photo: H. Zell; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/bittersweet-nightshade/).
- [Black henbane](https://denson.github.io/colorado-weed-field-guide/plants/black-henbane/) — *Hyoscyamus niger*. **Highly poisonous; keep animals away**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/black-henbane/index.md).
  ![Pale yellow henbane flowers with purple veins and dark purple throats above lobed leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/black-henbane.webp) Photo: H. Zell; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/black-henbane/).
- [Bohemian knotweed](https://denson.github.io/colorado-weed-field-guide/plants/bohemian-knotweed/) — *Reynoutria × bohemica*. **Hybrid regrows from small fragments**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/bohemian-knotweed/index.md).
  ![Reynoutria × bohemica: Young rounded leaves with reddish-purple tones and a folded emerging leaf.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/bohemian-knotweed.webp) Photo: Patrick Hacker; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/bohemian-knotweed/).
- [Bouncingbet](https://denson.github.io/colorado-weed-field-guide/plants/bouncingbet/) — *Saponaria officinalis*. **Saponins can cause digestive poisoning**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/bouncingbet/index.md).
  ![Upright soapwort stem with opposite leaves and a pale flower cluster in sandy ground.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/bouncingbet.webp) Photo: Ryan Hodnett; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/bouncingbet/).
- [Bulbous bluegrass](https://denson.github.io/colorado-weed-field-guide/plants/bulbous-bluegrass/) — *Poa bulbosa*. **Early-season grass spreads by bulbils**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/bulbous-bluegrass/index.md).
  ![Poa bulbosa: Low grass clump with slender upright culms and compact dark-tipped panicles.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/bulbous-bluegrass.webp) Photo: Stefan.lefnaer; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/bulbous-bluegrass/).
- [Bull thistle](https://denson.github.io/colorado-weed-field-guide/plants/bull-thistle/) — *Cirsium vulgare*. **Sharp spines; competes with vegetation**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/bull-thistle/index.md).
  ![Cirsium vulgare: White wind-dispersal hairs spreading from mature dry seed heads.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/bull-thistle.webp) Photo: Dominicus Johannes Bergsma; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/bull-thistle/).
- [Camelthorn](https://denson.github.io/colorado-weed-field-guide/plants/camelthorn/) — *Alhagi maurorum*. **Thorns and deep spreading roots**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/camelthorn/index.md).
  ![Alhagi maurorum: A dense, twiggy stand growing beside a paved edge.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/camelthorn.webp) Photo: Jesse Rorabaugh; CC0 1.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/camelthorn/).
- [Canada thistle](https://denson.github.io/colorado-weed-field-guide/plants/canada-thistle/) — *Cirsium arvense*. **Sharp spines; competes with vegetation**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/canada-thistle/index.md).
  ![Cirsium arvense: Branching stem carrying numerous small pink-purple flower heads and buds.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/canada-thistle.webp) Photo: Ivar Leidus; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/canada-thistle/).
- [Cheatgrass / downy brome](https://denson.github.io/colorado-weed-field-guide/plants/cheatgrass/) — *Bromus tectorum*. **Grass awns · Fire hazard**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/cheatgrass/index.md).
  ![Bromus tectorum: Green to purple awned spikelets hang from slender drooping panicle branches.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/cheatgrass.webp) Photo: AnRo0002; CC0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/cheatgrass/).
- [Chicory](https://denson.github.io/colorado-weed-field-guide/plants/chicory/) — *Cichorium intybus*. **Roadside and pasture spread**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/chicory/index.md).
  ![Cichorium intybus: Tall branched flowering plant above broad lower leaves at a grassy field edge.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/chicory.webp) Photo: H. Zell; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/chicory/).
- [Chinese clematis](https://denson.github.io/colorado-weed-field-guide/plants/chinese-clematis/) — *Clematis orientalis*. **Smothers vegetation; irritating plant compounds**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/chinese-clematis/index.md).
  ![Several clematis fruit clusters with long, silky, twisting tails on woody stems.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/chinese-clematis.webp) Photo: Krzysztof Ziarnek, Kenraiz; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/chinese-clematis/).
- [Common burdock](https://denson.github.io/colorado-weed-field-guide/plants/common-burdock/) — *Arctium minus*. **Burs and fine bristles injure animals**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-burdock/index.md).
  ![Arctium minus: Green spherical burs covered with long hooked bracts.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-burdock.webp) Photo: Isidre blanc; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-burdock/).
- [Common chickweed](https://denson.github.io/colorado-weed-field-guide/plants/common-chickweed/) — *Stellaria media*. **A cool-season weed that can seed while still small**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-chickweed/index.md).
  ![Stellaria media: A small flowering shoot held on a glove, showing white deeply divided petals, opposite leaves and buds.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-chickweed.webp) Photo: Forest and Kim Starr; CC BY 3.0 us. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-chickweed/).
- [Common cocklebur](https://denson.github.io/colorado-weed-field-guide/plants/common-cocklebur/) — *Xanthium strumarium*. **Burs catch in fur; seedlings and seeds are hazardous**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-cocklebur/index.md).
  ![Xanthium strumarium: Broad triangular to shallowly lobed leaf with coarse teeth and prominent veins.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-cocklebur.webp) Photo: Franco Folini; CC BY 2.5. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-cocklebur/).
- [Common crupina](https://denson.github.io/colorado-weed-field-guide/plants/common-crupina/) — *Crupina vulgaris*. **Dense stands reduce forage**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-crupina/index.md).
  ![Crupina vulgaris: An open fruiting head with conspicuous dark bristles.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-crupina.webp) Photo: Clément Maouche; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-crupina/).
- [Common dandelion](https://denson.github.io/colorado-weed-field-guide/plants/common-dandelion/) — *Taraxacum officinale*. **Persistent lawn volunteer; sap can irritate skin**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-dandelion/index.md).
  ![Taraxacum officinale: Whole photographed plant with a taproot, basal lobed leaves, and a leafless stalk bearing a yellow flower head.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-dandelion.webp) Photo: FoeNyx; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-dandelion/).
- [Common lambsquarters](https://denson.github.io/colorado-weed-field-guide/plants/common-lambsquarters/) — *Chenopodium album*. **Prolific garden weed; ingestion caution**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-lambsquarters/index.md).
  ![Chenopodium album: A broad-based, toothed leaf on an upright leafy stem.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-lambsquarters.webp) Photo: Matt Lavin; CC BY-SA 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-lambsquarters/).
- [Common mallow](https://denson.github.io/colorado-weed-field-guide/plants/common-mallow/) — *Malva neglecta*. **Tough taproot and persistent lawn seedbank**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-mallow/index.md).
  ![Malva neglecta: A small pale flower beneath rounded, shallowly lobed leaves with toothed edges.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-mallow.webp) Photo: NY State IPM Program  at Cornell University  from New York, USA; CC BY 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-mallow/).
- [Common mullein](https://denson.github.io/colorado-weed-field-guide/plants/common-mullein/) — *Verbascum thapsus*. **Dense rosettes and persistent volunteers**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-mullein/index.md).
  ![Verbascum thapsus: Tall yellow flowering spike above a column of broad pale woolly leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-mullein.webp) Photo: Isidre blanc; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-mullein/).
- [Common purslane](https://denson.github.io/colorado-weed-field-guide/plants/common-purslane/) — *Portulaca oleracea*. **Pet ingestion hazard despite human food uses**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-purslane/index.md).
  ![Portulaca oleracea: Small yellow flowers nestled among thick rounded succulent leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-purslane.webp) Photo: Isidre blanc; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-purslane/).
- [Common St. Johnswort](https://denson.github.io/colorado-weed-field-guide/plants/common-st-johnswort/) — *Hypericum perforatum*. **Photosensitivity and animal exposure concerns**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-st-johnswort/index.md).
  ![Hypericum perforatum: Five-petaled yellow flowers with numerous projecting stamens.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-st-johnswort.webp) Photo: W. Bulach; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-st-johnswort/).
- [Common tansy](https://denson.github.io/colorado-weed-field-guide/plants/common-tansy/) — *Tanacetum vulgare*. **Toxic ingestion; contact dermatitis**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-tansy/index.md).
  ![Close view of three yellow buttonlike tansy flower heads, showing tiny disk florets.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-tansy.webp) Photo: Agnes Monkelbaan; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-tansy/).
- [Common teasel](https://denson.github.io/colorado-weed-field-guide/plants/common-teasel/) — *Dipsacus fullonum*. **Prickly heads; prolific seed spread**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/common-teasel/index.md).
  ![Dipsacus fullonum: Tall erect teasel stem with opposite leaves and branching upper flower-head stalks.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/common-teasel.webp) Photo: Isidre blanc; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/common-teasel/).
- [Creeping woodsorrel](https://denson.github.io/colorado-weed-field-guide/plants/creeping-woodsorrel/) — *Oxalis corniculata*. **Oxalate-containing plant; keep pets from grazing**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/creeping-woodsorrel/index.md).
  ![Creeping woodsorrel: a low leafy patch of creeping woodsorrel with small yellow flowers.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/creeping-woodsorrel.webp) Photo: Forest & Kim Starr; CC BY 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/creeping-woodsorrel/).
- [Crownvetch](https://denson.github.io/colorado-weed-field-guide/plants/crownvetch/) — *Securigera varia*. **Toxic to horses; spreading roots can smother vegetation**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/crownvetch/index.md).
  ![Sprawling crownvetch stems with many pink-and-white flower clusters and pinnate leaves among other vegetation.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/crownvetch.webp) Photo: Dale Knox; CC0 1.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/crownvetch/).
- [Curly dock](https://denson.github.io/colorado-weed-field-guide/plants/curly-dock/) — *Rumex crispus*. **Soluble oxalates; persistent roots and seeds**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/curly-dock/index.md).
  ![Rumex crispus: A broad, branching fruiting plant in open disturbed ground.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/curly-dock.webp) Photo: Ayotte, Gilles, 1948-; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/curly-dock/).
- [Cutleaf teasel](https://denson.github.io/colorado-weed-field-guide/plants/cutleaf-teasel/) — *Dipsacus laciniatus*. **Prickly stands can displace native vegetation**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/cutleaf-teasel/index.md).
  ![Dry oval teasel head on a prickly stalk, with rigid bracts surrounding the head.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/cutleaf-teasel.webp) Photo: Alexander Klink; CC BY 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/cutleaf-teasel/).
- [Cypress spurge](https://denson.github.io/colorado-weed-field-guide/plants/cypress-spurge/) — *Euphorbia cyparissias*. **Sap can injure skin and eyes**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/cypress-spurge/index.md).
  ![Euphorbia cyparissias: Yellow-green floral bracts and small cyathia above many narrow leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/cypress-spurge.webp) Photo: Tom Scavo; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/cypress-spurge/).
- [Dalmatian toadflax](https://denson.github.io/colorado-weed-field-guide/plants/dalmatian-toadflax/) — *Linaria dalmatica*. **Spreads from roots; livestock concern**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/dalmatian-toadflax/index.md).
  ![Linaria dalmatica: Erect stem bearing a long series of yellow flowers and broad clasping leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/dalmatian-toadflax.webp) Photo: Walter Siegmund (talk); CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/dalmatian-toadflax/).
- [Dame’s rocket](https://denson.github.io/colorado-weed-field-guide/plants/dames-rocket/) — *Hesperis matronalis*. **Escapes gardens and spreads**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/dames-rocket/index.md).
  ![Hesperis matronalis: Upright stems with alternate lance-shaped leaves and branching clusters of lilac flowers.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/dames-rocket.webp) Photo: Anneli Salo; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/dames-rocket/).
- [Diffuse knapweed](https://denson.github.io/colorado-weed-field-guide/plants/diffuse-knapweed/) — *Centaurea diffusa*. **Skin irritation; tumbling seed spread**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/diffuse-knapweed/index.md).
  ![Dense, widely branched diffuse knapweed bearing many small pale flower heads; photographed at Williams Fork Reservoir, Colorado.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/diffuse-knapweed.webp) Photo: Kenraiz; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/diffuse-knapweed/).
- [Dyer’s woad](https://denson.github.io/colorado-weed-field-guide/plants/dyers-woad/) — *Isatis tinctoria*. **Persistent seed spread**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/dyers-woad/index.md).
  ![Isatis tinctoria: Branched clusters of small yellow flowers above blue-green foliage.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/dyers-woad.webp) Photo: Reuven Martin; CC0 1.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/dyers-woad/).
- [Elongated mustard](https://denson.github.io/colorado-weed-field-guide/plants/elongated-mustard/) — *Brassica elongata*. **Early detection priority in dry disturbed land**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/elongated-mustard/index.md).
  ![Brassica elongata: A branched stem with yellow flowers growing beside paving.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/elongated-mustard.webp) Photo: Dmitriy Bochkov; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/elongated-mustard/).
- [Eurasian watermilfoil](https://denson.github.io/colorado-weed-field-guide/plants/eurasian-watermilfoil/) — *Myriophyllum spicatum*. **Fragments spread dense aquatic growth**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/eurasian-watermilfoil/index.md).
  ![A watermilfoil shoot at the water surface with a small flower spike rising above the water.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/eurasian-watermilfoil.webp) Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org; CC BY 3.0 us. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/eurasian-watermilfoil/).
- [Field bindweed](https://denson.github.io/colorado-weed-field-guide/plants/field-bindweed/) — *Convolvulus arvensis*. **Smothers plants; livestock concern**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/field-bindweed/index.md).
  ![Convolvulus arvensis: Pale pink funnel-shaped flowers with darker pink bands and nearby arrow-shaped leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/field-bindweed.webp) Photo: Svklimkin; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/field-bindweed/).
- [Flowering rush](https://denson.github.io/colorado-weed-field-guide/plants/flowering-rush/) — *Butomus umbellatus*. **Small fragments spread aquatic colonies**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/flowering-rush/index.md).
  ![Butomus umbellatus: A cluster of pale pink flowers and buds held on radiating stalks beside open water.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/flowering-rush.webp) Photo: Jacek Pietruszewski; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/flowering-rush/).
- [Giant knotweed](https://denson.github.io/colorado-weed-field-guide/plants/giant-knotweed/) — *Reynoutria sachalinensis*. **Very persistent riparian colonies**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/giant-knotweed/index.md).
  ![Reynoutria sachalinensis: Upright shoots with broad, heart-based leaves among mixed ground vegetation.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/giant-knotweed.webp) Photo: Oleksandr Shynder; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/giant-knotweed/).
- [Giant reed](https://denson.github.io/colorado-weed-field-guide/plants/giant-reed/) — *Arundo donax*. **Dense stands displace riparian plants**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/giant-reed/index.md).
  ![Arundo donax: A dense stand of tall, jointed canes and long leaves near water.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/giant-reed.webp) Photo: zebedeugalinha; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/giant-reed/).
- [Giant salvinia](https://denson.github.io/colorado-weed-field-guide/plants/giant-salvinia/) — *Salvinia molesta*. **Floating mats harm aquatic habitat**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/giant-salvinia/index.md).
  ![Salvinia molesta: Close view of floating, folded green leaves with textured upper surfaces.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/giant-salvinia.webp) Photo: Ixitixel; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/giant-salvinia/).
- [Green foxtail](https://denson.github.io/colorado-weed-field-guide/plants/green-foxtail/) — *Setaria viridis*. **Identify the grass behind the name “foxtail”**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/green-foxtail/index.md).
  ![Green foxtail: a curved green flower head is surrounded by many long fine bristles.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/green-foxtail.webp) Photo: Petr Filippov; CC BY 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/green-foxtail/).
- [Hairy willow-herb](https://denson.github.io/colorado-weed-field-guide/plants/hairy-willow-herb/) — *Epilobium hirsutum*. **Spreads through wetland vegetation**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/hairy-willow-herb/index.md).
  ![Epilobium hirsutum: A serrated leaf and visibly hairy stem among surrounding vegetation.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/hairy-willow-herb.webp) Photo: Mathias keraudren; CC0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/hairy-willow-herb/).
- [Halogeton](https://denson.github.io/colorado-weed-field-guide/plants/halogeton/) — *Halogeton glomeratus*. **Severe oxalate poisoning in livestock**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/halogeton/index.md).
  ![Halogeton glomeratus: Small fleshy cylindrical blue-green leaves cluster along a reddish stem.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/halogeton.webp) Photo: Matt Lavin from Bozeman, Montana, USA; CC BY-SA 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/halogeton/).
- [Henbit](https://denson.github.io/colorado-weed-field-guide/plants/henbit/) — *Lamium amplexicaule*. **An early-flowering weed with useful nectar**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/henbit/index.md).
  ![Lamium amplexicaule: Several long purple tubular flowers rising from a whorl of rounded clasping leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/henbit.webp) Photo: Patrick Alexander  from Las Cruces, NM; CC0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/henbit/).
- [Hoary cress](https://denson.github.io/colorado-weed-field-guide/plants/hoary-cress/) — *Lepidium draba*. **Spreading roots; possible livestock poisoning**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/hoary-cress/index.md).
  ![A dense patch of whitetop in bloom, with broad white flower clusters above green leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/hoary-cress.webp) Photo: Katrin Schneider / korina.info; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/hoary-cress/).
- [Houndstongue](https://denson.github.io/colorado-weed-field-guide/plants/houndstongue/) — *Cynoglossum officinale*. **Toxic to livestock**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/houndstongue/index.md).
  ![Cynoglossum officinale: Upright leafy flowering plant with broad lance-shaped foliage and branched upper flower stems.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/houndstongue.webp) Photo: Bernd Haynold; CC BY 2.5. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/houndstongue/).
- [Spotted × diffuse knapweed hybrid](https://denson.github.io/colorado-weed-field-guide/plants/hybrid-knapweed/) — *Centaurea × psammogena*. **Hybrid identification needs expert review**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/hybrid-knapweed/index.md).
  ![A pink-purple hybrid-knapweed head and several buds held beside branching stems; the source identifies this Littleton, Colorado plant as Centaurea × psammogena.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/hybrid-knapweed.webp) Photo: Tyler; CC0 1.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/hybrid-knapweed/).
- [Yellow × Dalmatian toadflax hybrid](https://denson.github.io/colorado-weed-field-guide/plants/hybrid-toadflax/) — *Linaria vulgaris × Linaria dalmatica*. **Variable hybrid; persistent spreading roots**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/hybrid-toadflax/index.md).
  ![Several fresh hybrid-toadflax shoots with variable, relatively broad leaves, photographed against a white background.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/hybrid-toadflax.webp) Photo: Sharlene E. Sing, USDA Forest Service, Rocky Mountain Research Station; Public domain (U.S. federal employee work). [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/hybrid-toadflax/).
- [Hydrilla](https://denson.github.io/colorado-weed-field-guide/plants/hydrilla/) — *Hydrilla verticillata*. **Dense aquatic growth; wildlife disease association**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/hydrilla/index.md).
  ![Hydrilla verticillata: A wet stem tip with short leaves in whorls and toothed leaf margins.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/hydrilla.webp) Photo: Stanislav Murashkin; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/hydrilla/).
- [Japanese knotweed](https://denson.github.io/colorado-weed-field-guide/plants/japanese-knotweed/) — *Reynoutria japonica*. **Root and stem fragments regrow**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/japanese-knotweed/index.md).
  ![Reynoutria japonica: Broad pointed leaves and pale flower clusters viewed against the light.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/japanese-knotweed.webp) Photo: Michael Gasperl ( Migas ); CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/japanese-knotweed/).
- [Jimsonweed](https://denson.github.io/colorado-weed-field-guide/plants/jimsonweed/) — *Datura stramonium*. **Serious poisoning risk to people and animals**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/jimsonweed/index.md).
  ![Datura stramonium: Bushy plant with coarsely toothed broad leaves and upright white flowers.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/jimsonweed.webp) Photo: H. Zell; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/jimsonweed/).
- [Johnsongrass](https://denson.github.io/colorado-weed-field-guide/plants/johnsongrass/) — *Sorghum halepense*. **Livestock cyanide risk; added fire fuel**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/johnsongrass/index.md).
  ![Sorghum halepense: Close view of grass spikelets with dangling reddish anthers.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/johnsongrass.webp) Photo: Jim Conrad; Public domain. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/johnsongrass/).
- [Jointed goatgrass](https://denson.github.io/colorado-weed-field-guide/plants/jointed-goatgrass/) — *Aegilops cylindrica*. **Wheat-field and rangeland seed spread**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/jointed-goatgrass/index.md).
  ![A stand of slender green jointed-goatgrass stems with narrow cylindrical spikes.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/jointed-goatgrass.webp) Photo: Stefan.lefnaer; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/jointed-goatgrass/).
- [Kochia](https://denson.github.io/colorado-weed-field-guide/plants/kochia/) — *Bassia scoparia*. **Tumbling seed spread; livestock poisoning risk**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/kochia/index.md).
  ![Bassia scoparia: Upright bushy green plant with many narrow leaves on densely branched stems.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/kochia.webp) Photo: WildBoar; Public domain. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/kochia/).
- [Large crabgrass](https://denson.github.io/colorado-weed-field-guide/plants/large-crabgrass/) — *Digitaria sanguinalis*. **Fast seed production in thin lawns**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/large-crabgrass/index.md).
  ![Large crabgrass: a low spreading grass clump with green leaf blades and long radiating stems on bare soil.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/large-crabgrass.webp) Photo: Rasbak; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/large-crabgrass/).
- [Leafy spurge](https://denson.github.io/colorado-weed-field-guide/plants/leafy-spurge/) — *Euphorbia esula*. **Irritating sap; eye injury risk**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/leafy-spurge/index.md).
  ![Euphorbia esula: Dense upright leafy stems topped with yellow-green flower clusters.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/leafy-spurge.webp) Photo: H. Zell; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/leafy-spurge/).
- [Mayweed chamomile](https://denson.github.io/colorado-weed-field-guide/plants/mayweed-chamomile/) — *Anthemis cotula*. **Crop weed with unpleasant-smelling foliage**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/mayweed-chamomile/index.md).
  ![Mayweed chamomile heads with white rays around raised yellow centers.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/mayweed-chamomile.webp) Photo: NY State IPM Program at Cornell University from New York, USA; CC BY 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/mayweed-chamomile/).
- [Meadow knapweed](https://denson.github.io/colorado-weed-field-guide/plants/meadow-knapweed/) — *Centaurea × moncktonii*. **Outcompetes pasture and meadow plants**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/meadow-knapweed/index.md).
  ![Centaurea × moncktonii: A purple flower head among additional buds and spent heads.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/meadow-knapweed.webp) Photo: Eric Coombs, Oregon Department of Agriculture, Bugwood.org; CC BY 3.0 us. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/meadow-knapweed/).
- [Mediterranean sage](https://denson.github.io/colorado-weed-field-guide/plants/mediterranean-sage/) — *Salvia aethiopis*. **Tumbles and spreads seed through rangeland**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/mediterranean-sage/index.md).
  ![Salvia aethiopis: A pale, branching flowering plant in open grassland.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/mediterranean-sage.webp) Photo: Stefan.lefnaer; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/mediterranean-sage/).
- [Medusahead](https://denson.github.io/colorado-weed-field-guide/plants/medusahead/) — *Taeniatherum caput-medusae*. **Barbed awns; persistent fire-promoting thatch**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/medusahead/index.md).
  ![Taeniatherum caput-medusae: Dense grass growth with numerous pale, spreading, long-awned heads.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/medusahead.webp) Photo: Matt Lavin  from Bozeman, Montana, USA; CC BY-SA 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/medusahead/).
- [Moth mullein](https://denson.github.io/colorado-weed-field-guide/plants/moth-mullein/) — *Verbascum blattaria*. **Long-lived seeds sustain infestations**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/moth-mullein/index.md).
  ![Round dry moth-mullein capsules on short stalks beside a slender main stem, with a 10 mm scale.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/moth-mullein.webp) Photo: Stefan.lefnaer; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/moth-mullein/).
- [Musk thistle](https://denson.github.io/colorado-weed-field-guide/plants/musk-thistle/) — *Carduus nutans*. **Sharp spines; competes with vegetation**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/musk-thistle/index.md).
  ![Carduus nutans: Nodding purple flower head on a curved stalk with pointed involucral bracts.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/musk-thistle.webp) Photo: Robert Flogaus-Faust; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/musk-thistle/).
- [Myrtle spurge](https://denson.github.io/colorado-weed-field-guide/plants/myrtle-spurge/) — *Euphorbia myrsinites*. **Poisonous · Eye & skin injury**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/myrtle-spurge/index.md).
  ![Euphorbia myrsinites: Close view of yellow-green bracts and small cup-shaped cyathia.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/myrtle-spurge.webp) Photo: Flocci Nivis; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/myrtle-spurge/).
- [Narrow-leaved Dalmatian toadflax](https://denson.github.io/colorado-weed-field-guide/plants/narrow-leaved-dalmatian-toadflax/) — *Linaria genistifolia*. **Listed taxon with difficult identification**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/narrow-leaved-dalmatian-toadflax/index.md).
  ![Side view of yellow toadflax flowers and their long spurs beside developing reproductive structures, with a 10 mm scale.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/narrow-leaved-dalmatian-toadflax.webp) Photo: Stefan.lefnaer; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/narrow-leaved-dalmatian-toadflax/).
- [Orange hawkweed](https://denson.github.io/colorado-weed-field-guide/plants/orange-hawkweed/) — *Pilosella aurantiaca*. **Runners crowd lawns and mountain meadows**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/orange-hawkweed/index.md).
  ![Pilosella aurantiaca: A compact group of bright orange-red flower heads with yellow centres.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/orange-hawkweed.webp) Photo: Tom Norton; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/orange-hawkweed/).
- [Oxeye daisy](https://denson.github.io/colorado-weed-field-guide/plants/oxeye-daisy/) — *Leucanthemum vulgare*. **Toxic to dogs and cats; dermatitis**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/oxeye-daisy/index.md).
  ![Leucanthemum vulgare: Upright clump with many long stems carrying white-rayed yellow-centered flower heads.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/oxeye-daisy.webp) Photo: Isidre blanc; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/oxeye-daisy/).
- [Parrotfeather](https://denson.github.io/colorado-weed-field-guide/plants/parrotfeather/) — *Myriophyllum aquaticum*. **Aquatic mats obstruct waterways**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/parrotfeather/index.md).
  ![Myriophyllum aquaticum: Dense green, feather-leaved shoots emerging above the water surface.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/parrotfeather.webp) Photo: Quillipede; CC0 1.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/parrotfeather/).
- [Perennial pepperweed](https://denson.github.io/colorado-weed-field-guide/plants/perennial-pepperweed/) — *Lepidium latifolium*. **Deep roots form persistent wetland colonies**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/perennial-pepperweed/index.md).
  ![A fruiting perennial-pepperweed branch bearing many small green oval fruits.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/perennial-pepperweed.webp) Photo: Ayotte, Gilles, 1948-; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/perennial-pepperweed/).
- [Perennial sowthistle](https://denson.github.io/colorado-weed-field-guide/plants/perennial-sowthistle/) — *Sonchus arvensis*. **Persistent underground spread**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/perennial-sowthistle/index.md).
  ![Sonchus arvensis: Branched upright sowthistle bearing yellow flower heads above deeply lobed foliage.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/perennial-sowthistle.webp) Photo: Gabriele Kothe-Heinrich; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/perennial-sowthistle/).
- [Plumeless thistle](https://denson.github.io/colorado-weed-field-guide/plants/plumeless-thistle/) — *Carduus acanthoides*. **Sharp spines; pasture competition**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/plumeless-thistle/index.md).
  ![Flatbed photographic scan of a deeply lobed, spiny plumeless-thistle leaf with a millimeter scale.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/plumeless-thistle.webp) Photo: Dmitry Makeev; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/plumeless-thistle/).
- [Poison hemlock](https://denson.github.io/colorado-weed-field-guide/plants/poison-hemlock/) — *Conium maculatum*. **Poisonous to people & animals**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/poison-hemlock/index.md).
  ![Conium maculatum: Tall branching plant with many small white compound umbels above finely divided foliage.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/poison-hemlock.webp) Photo: Krzysztof Ziarnek, Kenraiz; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/poison-hemlock/).
- [Prickly lettuce](https://denson.github.io/colorado-weed-field-guide/plants/prickly-lettuce/) — *Lactuca serriola*. **Prickly leaves and prolific windborne seed**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/prickly-lettuce/index.md).
  ![Prickly lettuce: a pale yellow flower head composed of narrow strap-shaped florets.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/prickly-lettuce.webp) Photo: Teun Spaans (TeunSpaans); Public domain. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/prickly-lettuce/).
- [Prickly sowthistle](https://denson.github.io/colorado-weed-field-guide/plants/prickly-sowthistle/) — *Sonchus asper*. **Spiny leaves and rapid seed production**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/prickly-sowthistle/index.md).
  ![Sonchus asper: A tall flowering prickly sow-thistle with lobed leaves beside a tree trunk.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/prickly-sowthistle.webp) Photo: Didier Descouens; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/prickly-sowthistle/).
- [Prostrate knotweed](https://denson.github.io/colorado-weed-field-guide/plants/prostrate-knotweed/) — *Polygonum aviculare*. **A mat-forming weed of compacted ground**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/prostrate-knotweed/index.md).
  ![Prostrate knotweed: a flattened mat of branching stems and small leaves spreads across bare soil.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/prostrate-knotweed.webp) Photo: Rasbak; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/prostrate-knotweed/).
- [Puncturevine / goathead](https://denson.github.io/colorado-weed-field-guide/plants/puncturevine/) — *Tribulus terrestris*. **Sharp burs · Animal injury**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/puncturevine/index.md).
  ![Tribulus terrestris: Five-petaled pale yellow flower beside hairy leaves with paired oval leaflets.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/puncturevine.webp) Photo: Forest & Kim Starr; CC BY 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/puncturevine/).
- [Purple loosestrife](https://denson.github.io/colorado-weed-field-guide/plants/purple-loosestrife/) — *Lythrum salicaria*. **Crowds out wetland vegetation**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/purple-loosestrife/index.md).
  ![Lythrum salicaria: Close view of a purple flower with narrow petals and projecting stamens.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/purple-loosestrife.webp) Photo: Douglas Goldman; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/purple-loosestrife/).
- [Quackgrass](https://denson.github.io/colorado-weed-field-guide/plants/quackgrass/) — *Elymus repens*. **Rhizome fragments regrow in lawns and gardens**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/quackgrass/index.md).
  ![Elymus repens: Dense upright grass clump with long green blades and slender flower spikes.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/quackgrass.webp) Photo: Rasbak; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/quackgrass/).
- [Redroot pigweed](https://denson.github.io/colorado-weed-field-guide/plants/redroot-pigweed/) — *Amaranthus retroflexus*. **Crop competition; nitrate and oxalate livestock risk**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/redroot-pigweed/index.md).
  ![Amaranthus retroflexus: Upright plant with alternate broad leaves and a dense green terminal flower spike.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/redroot-pigweed.webp) Photo: Lynk media; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/redroot-pigweed/).
- [Redstem filaree](https://denson.github.io/colorado-weed-field-guide/plants/redstem-filaree/) — *Erodium cicutarium*. **Seeds spread through lawns and pasture**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/redstem-filaree/index.md).
  ![Erodium cicutarium: Cluster of long narrow beaked fruits above divided foliage.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/redstem-filaree.webp) Photo: Follavoine / follavoine.net; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/redstem-filaree/).
- [Rush skeletonweed](https://denson.github.io/colorado-weed-field-guide/plants/rush-skeletonweed/) — *Chondrilla juncea*. **Deep roots and fragments sustain spread**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/rush-skeletonweed/index.md).
  ![Chondrilla juncea: A small yellow flower head beside narrow buds on nearly leafless branching stems.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/rush-skeletonweed.webp) Photo: Zihao Wang; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/rush-skeletonweed/).
- [Russian knapweed](https://denson.github.io/colorado-weed-field-guide/plants/russian-knapweed/) — *Rhaponticum repens*. **Toxic to horses**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/russian-knapweed/index.md).
  ![Rhaponticum repens: Dense patch of upright gray-green leafy plants beneath trees.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/russian-knapweed.webp) Photo: Amirh. absnd; CC0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/russian-knapweed/).
- [Russian olive](https://denson.github.io/colorado-weed-field-guide/plants/russian-olive/) — *Elaeagnus angustifolia*. **Thorns; riparian habitat concern**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/russian-olive/index.md).
  ![Elaeagnus angustifolia: Small yellow flowers and narrow silvery leaves on a twig.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/russian-olive.webp) Photo: Georg Slickers; CC BY-SA 2.5. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/russian-olive/).
- [Russian thistle](https://denson.github.io/colorado-weed-field-guide/plants/russian-thistle/) — *Salsola tragus*. **Prickly tumbleweeds; livestock and fire hazards**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/russian-thistle/index.md).
  ![Salsola tragus: Rounded, densely branched green plant with slender leaves and spiny-looking branch tips.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/russian-thistle.webp) Photo: Stefan.lefnaer; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/russian-thistle/).
- [Scentless chamomile](https://denson.github.io/colorado-weed-field-guide/plants/scentless-chamomile/) — *Tripleurospermum inodorum*. **Prolific seeds; reported livestock irritation**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/scentless-chamomile/index.md).
  ![A low branching scentless-chamomile plant with many white-and-yellow flower heads on bare ground.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/scentless-chamomile.webp) Photo: Krzysztof Ziarnek, Kenraiz; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/scentless-chamomile/).
- [Scotch thistle](https://denson.github.io/colorado-weed-field-guide/plants/scotch-thistle/) — *Onopordum acanthium*. **Sharp spines; competes with vegetation**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/scotch-thistle/index.md).
  ![Onopordum acanthium: Pale woolly young leaf with deeply lobed spine-tipped margins and a prominent light midrib.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/scotch-thistle.webp) Photo: Krzysztof Ziarnek, Kenraiz; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/scotch-thistle/).
- [Shepherd’s purse](https://denson.github.io/colorado-weed-field-guide/plants/shepherds-purse/) — *Capsella bursa-pastoris*. **An early-seeding lawn and garden weed**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/shepherds-purse/index.md).
  ![Shepherd’s-purse: a flat basal rosette of deeply lobed leaves spreads over bare soil.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/shepherds-purse.webp) Photo: Rasbak; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/shepherds-purse/).
- [Siberian elm](https://denson.github.io/colorado-weed-field-guide/plants/siberian-elm/) — *Ulmus pumila*. **Numerous seedlings; weak branches**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/siberian-elm/index.md).
  ![Ulmus pumila: Clusters of pale green round winged fruits on a twig.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/siberian-elm.webp) Photo: Shizhao; CC BY-SA 2.5. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/siberian-elm/).
- [Spotted knapweed](https://denson.github.io/colorado-weed-field-guide/plants/spotted-knapweed/) — *Centaurea stoebe*. **Competes with native vegetation**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/spotted-knapweed/index.md).
  ![Centaurea stoebe: Close view of the purple tubular florets forming a knapweed flower head.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/spotted-knapweed.webp) Photo: Alan Vernon; CC BY 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/spotted-knapweed/).
- [Squarrose knapweed](https://denson.github.io/colorado-weed-field-guide/plants/squarrose-knapweed/) — *Centaurea virgata*. **Spiny seedheads; loss of rangeland forage**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/squarrose-knapweed/index.md).
  ![Centaurea virgata: A small pink-purple flower head and slender leafy stem held in front of a hand.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/squarrose-knapweed.webp) Photo: Alexander Dubynin; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/squarrose-knapweed/).
- [Sulfur cinquefoil](https://denson.github.io/colorado-weed-field-guide/plants/sulfur-cinquefoil/) — *Potentilla recta*. **Persistent pasture and roadside weed**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/sulfur-cinquefoil/index.md).
  ![A pale yellow, five-petaled sulphur-cinquefoil flower showing its central stamens.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/sulfur-cinquefoil.webp) Photo: Matt Lavin from Bozeman, Montana, USA; CC BY-SA 2.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/sulfur-cinquefoil/).
- [Tall buttercup](https://denson.github.io/colorado-weed-field-guide/plants/tall-buttercup/) — *Ranunculus acris*. **Fresh plant irritation and animal poisoning hazard**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/tall-buttercup/index.md).
  ![Meadow buttercup growing among grass, with yellow flowers held above deeply divided basal leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/tall-buttercup.webp) Photo: Daniel Cahen; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/tall-buttercup/).
- [Tamarisk](https://denson.github.io/colorado-weed-field-guide/plants/tamarisk/) — *Tamarix ramosissima*. **Alters riparian vegetation**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/tamarisk/index.md).
  ![Tamarix ramosissima: Slender pink flower racemes on fine twiggy branches.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/tamarisk.webp) Photo: Jerzy Opioła; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/tamarisk/).
- [Tansy ragwort](https://denson.github.io/colorado-weed-field-guide/plants/tansy-ragwort/) — *Jacobaea vulgaris*. **Poisonous to livestock; harmful alkaloids**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/tansy-ragwort/index.md).
  ![Jacobaea vulgaris: An upright flowering plant with yellow heads and deeply divided leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/tansy-ragwort.webp) Photo: jamie-aa; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/tansy-ragwort/).
- [Taurian thistle](https://denson.github.io/colorado-weed-field-guide/plants/taurian-thistle/) — *Onopordum tauricum*. **Sharp spines; taxon listed as Scotch thistle**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/taurian-thistle/index.md).
  ![A purple Taurian-thistle head with long pointed bracts beneath it.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/taurian-thistle.webp) Photo: Louis Aureglia; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/taurian-thistle/).
- [Tree of heaven](https://denson.github.io/colorado-weed-field-guide/plants/tree-of-heaven/) — *Ailanthus altissima*. **Root suckers form persistent thickets**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/tree-of-heaven/index.md).
  ![Ailanthus altissima: Mature tree with a broad rounded leafy crown and single trunk.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/tree-of-heaven.webp) Photo: Darkone; CC BY-SA 2.5. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/tree-of-heaven/).
- [Tumble mustard](https://denson.github.io/colorado-weed-field-guide/plants/tumble-mustard/) — *Sisymbrium altissimum*. **Another tumbleweed: brittle plants scatter persistent seed**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/tumble-mustard/index.md).
  ![Tall, finely branched tumble mustard plant carrying many small yellow flowers.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/tumble-mustard.webp) Photo: Ben Keen; CC0 1.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/tumble-mustard/).
- [Velvetleaf](https://denson.github.io/colorado-weed-field-guide/plants/velvetleaf/) — *Abutilon theophrasti*. **Persistent seeds and strong crop competition**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/velvetleaf/index.md).
  ![Abutilon theophrasti: Small yellow five-petaled flower among broad softly hairy heart-shaped leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/velvetleaf.webp) Photo: Salicyna; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/velvetleaf/).
- [Ventenata](https://denson.github.io/colorado-weed-field-guide/plants/ventenata/) — *Ventenata dubia*. **Displaces forage and native grassland**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/ventenata/index.md).
  ![Ventenata dubia: An open, delicate panicle of pale grass spikelets held against a mountain landscape.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/ventenata.webp) Photo: Matt Lavin; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/ventenata/).
- [White clover](https://denson.github.io/colorado-weed-field-guide/plants/white-clover/) — *Trifolium repens*. **A spreading lawn plant with pollinator value**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/white-clover/index.md).
  ![White clover: a rounded flower head of small white pea-like florets on a slender stalk.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/white-clover.webp) Photo: Ivar Leidus; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/white-clover/).
- [White sweetclover](https://denson.github.io/colorado-weed-field-guide/plants/white-sweetclover/) — *Melilotus albus*. **Moldy sweetclover hay can cause dangerous bleeding**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/white-sweetclover/index.md).
  ![Melilotus albus: Small white flowers on slender racemes above three-part leaves.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/white-sweetclover.webp) Photo: zebedeugalinha; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/white-sweetclover/).
- [Wild caraway](https://denson.github.io/colorado-weed-field-guide/plants/wild-caraway/) — *Carum carvi*. **Spreads by seed; pet safety concern**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/wild-caraway/index.md).
  ![Developing ribbed caraway fruits on the radiating stalks of a compound umbel.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/wild-caraway.webp) Photo: Ayotte, Gilles, 1948-; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/wild-caraway/).
- [Wild carrot](https://denson.github.io/colorado-weed-field-guide/plants/wild-carrot/) — *Daucus carota*. **Do not confuse it with highly poisonous hemlocks**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/wild-carrot/index.md).
  ![Daucus carota: A white compound umbel with a dark central flower and radiating flower clusters; the source identifies Daucus carota carota.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/wild-carrot.webp) Photo: zebedeugalinha; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/wild-carrot/).
- [Wild parsnip](https://denson.github.io/colorado-weed-field-guide/plants/wild-parsnip/) — *Pastinaca sativa*. **Sap plus sunlight can cause severe skin burns**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/wild-parsnip/index.md).
  ![Pastinaca sativa: A tall branched stem with compound leaves and small yellow umbels, shown against the sky.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/wild-parsnip.webp) Photo: Stefan.lefnaer; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/wild-parsnip/).
- [Wild proso millet](https://denson.github.io/colorado-weed-field-guide/plants/wild-proso-millet/) — *Panicum miliaceum*. **Seed contamination and crop competition**. State management: [List C — Manage widespread weeds](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/wild-proso-millet/index.md).
  ![Panicum miliaceum: Pale mature grains hang along densely branched drooping panicles.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/wild-proso-millet.webp) Photo: Kurt Stüber; CC BY-SA 3.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/wild-proso-millet/).
- [Yellow flag iris](https://denson.github.io/colorado-weed-field-guide/plants/yellow-flag-iris/) — *Iris pseudacorus*. **Ingestion concern; invasive wetland colonies**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/yellow-flag-iris/index.md).
  ![Iris pseudacorus: A yellow iris flower with dark markings on the large drooping segment.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/yellow-flag-iris.webp) Photo: Kailey Alderfer; CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/yellow-flag-iris/).
- [Yellow nutsedge](https://denson.github.io/colorado-weed-field-guide/plants/yellow-nutsedge/) — *Cyperus esculentus*. **Underground tubers sustain infestations**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/yellow-nutsedge/index.md).
  ![Yellow nutsedge with upright leafy stems and radiating yellow-green spikelet clusters.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/yellow-nutsedge.webp) Photo: Krzysztof Ziarnek, Kenraiz; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/yellow-nutsedge/).
- [Yellow starthistle](https://denson.github.io/colorado-weed-field-guide/plants/yellow-starthistle/) — *Centaurea solstitialis*. **Severe horse poisoning; sharp spines**. State management: [List A — Eradicate](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/yellow-starthistle/index.md).
  ![Centaurea solstitialis: A bright yellow flower head beside a dry head, showing the long radiating spines.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/yellow-starthistle.webp) Photo: Юрий Данилевский (Yuriy Danilevsky); CC BY 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/yellow-starthistle/).
- [Yellow sweetclover](https://denson.github.io/colorado-weed-field-guide/plants/yellow-sweetclover/) — *Melilotus officinalis*. **Moldy sweetclover hay can cause dangerous bleeding**. [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/yellow-sweetclover/index.md).
  ![Yellow sweetclover: small yellow pea-like flowers hang along a narrow elongated raceme.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/yellow-sweetclover.webp) Photo: Isidre blanc; CC BY-SA 4.0. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/yellow-sweetclover/).
- [Yellow toadflax](https://denson.github.io/colorado-weed-field-guide/plants/yellow-toadflax/) — *Linaria vulgaris*. **Spreads from roots; livestock concern**. State management: [List B — Stop the spread](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). [Full Markdown profile](https://denson.github.io/colorado-weed-field-guide/plants/yellow-toadflax/index.md).
  ![Linaria vulgaris: Close view of pale yellow two-lipped flowers with orange-yellow throats.](https://denson.github.io/colorado-weed-field-guide/assets/thumbs/yellow-toadflax.webp) Photo: Michael H. Lemmer; CC BY-SA 2.5. [Photo credits and sources](https://denson.github.io/colorado-weed-field-guide/plants/yellow-toadflax/).


# Appendix for agents

Category membership is editorial navigation. Native plants can also be xeriscape plants; noxious-list class is separate from toxicity. Follow the individual profiles for claim scope, caveats, and photo attribution. This is a selected catalog, not the entire Colorado flora.


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Canonical HTML: https://denson.github.io/colorado-weed-field-guide/

Content revised: 2026-09-21T19:48:00Z

Markdown mirror: https://denson.github.io/colorado-weed-field-guide/index.md

Text fallback: https://denson.github.io/colorado-weed-field-guide/index.md.txt

Agent entry: https://denson.github.io/colorado-weed-field-guide/start.md

Provenance: https://denson.github.io/colorado-weed-field-guide/provenance.json