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# Invasive & common weeds

State-listed noxious plants and common garden, crop and disturbed-ground weeds. Navigation does not assign native status or equal invasiveness to every plant. Legal weed class and toxicity are separate.

111 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/)

## 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/invasive/

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

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

Text fallback: https://denson.github.io/colorado-weed-field-guide/invasive/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