Invasive & common weeds

Photo: Agnieszka Kwiecień, Nova · CC BY-SA 4.0 · Credits and sources

African rue

Peganum harmala

Highly poisonous if eaten; deep-rooted invader

Photo: Alex Abair · CC BY 4.0 · Credits and sources

Annual sowthistle

Sonchus oleraceus

Windborne seed and crop-pest hosting

Photo: Miwasatoshi · CC BY-SA 4.0 · Credits and sources

Bittersweet nightshade

Solanum dulcamara

Poisonous berries and foliage

Photo: H. Zell · CC BY-SA 3.0 · Credits and sources

Pale yellow henbane flowers with purple veins and dark purple throats above lobed leaves.

Black henbane

Hyoscyamus niger

Highly poisonous; keep animals away

Photo: H. Zell · CC BY-SA 3.0 · Credits and sources

Bohemian knotweed

Reynoutria × bohemica

Hybrid regrows from small fragments

Photo: Patrick Hacker · CC BY 4.0 · Credits and sources

Upright soapwort stem with opposite leaves and a pale flower cluster in sandy ground.

Bouncingbet

Saponaria officinalis

Saponins can cause digestive poisoning

Photo: Ryan Hodnett · CC BY-SA 4.0 · Credits and sources

Bulbous bluegrass

Poa bulbosa

Early-season grass spreads by bulbils

Photo: Stefan.lefnaer · CC BY-SA 4.0 · Credits and sources

Bull thistle

Cirsium vulgare

Sharp spines; competes with vegetation

Photo: Dominicus Johannes Bergsma · CC BY-SA 4.0 · Credits and sources

Camelthorn

Alhagi maurorum

Thorns and deep spreading roots

Photo: Jesse Rorabaugh · CC0 1.0 · Credits and sources

Canada thistle

Cirsium arvense

Sharp spines; competes with vegetation

Photo: Ivar Leidus · CC BY-SA 3.0 · Credits and sources

Cheatgrass / downy brome

Bromus tectorum

Grass awns · Fire hazard

Photo: AnRo0002 · CC0 · Credits and sources

Chicory

Cichorium intybus

Roadside and pasture spread

Photo: H. Zell · CC BY-SA 3.0 · Credits and sources

Several clematis fruit clusters with long, silky, twisting tails on woody stems.

Chinese clematis

Clematis orientalis

Smothers vegetation; irritating plant compounds

Photo: Krzysztof Ziarnek, Kenraiz · CC BY-SA 4.0 · Credits and sources

Common burdock

Arctium minus

Burs and fine bristles injure animals

Photo: Isidre blanc · CC BY-SA 4.0 · Credits and sources

Common chickweed

Stellaria media

A cool-season weed that can seed while still small

Photo: Forest and Kim Starr · CC BY 3.0 us · Credits and sources

Common cocklebur

Xanthium strumarium

Burs catch in fur; seedlings and seeds are hazardous

Photo: Franco Folini · CC BY 2.5 · Credits and sources

Common crupina

Crupina vulgaris

Dense stands reduce forage

Photo: Clément Maouche · CC BY 4.0 · Credits and sources

Common dandelion

Taraxacum officinale

Persistent lawn volunteer; sap can irritate skin

Photo: FoeNyx · CC BY-SA 3.0 · Credits and sources

Common lambsquarters

Chenopodium album

Prolific garden weed; ingestion caution

Photo: Matt Lavin · CC BY-SA 2.0 · Credits and sources

Common mallow

Malva neglecta

Tough taproot and persistent lawn seedbank

Photo: NY State IPM Program at Cornell University from New York, USA · CC BY 2.0 · Credits and sources

Common mullein

Verbascum thapsus

Dense rosettes and persistent volunteers

Photo: Isidre blanc · CC BY-SA 4.0 · Credits and sources

Common purslane

Portulaca oleracea

Pet ingestion hazard despite human food uses

Photo: Isidre blanc · CC BY-SA 4.0 · Credits and sources

Common St. Johnswort

Hypericum perforatum

Photosensitivity and animal exposure concerns

Photo: W. Bulach · CC BY-SA 4.0 · Credits and sources

Close view of three yellow buttonlike tansy flower heads, showing tiny disk florets.

Common tansy

Tanacetum vulgare

Toxic ingestion; contact dermatitis

Photo: Agnes Monkelbaan · CC BY-SA 4.0 · Credits and sources

Common teasel

Dipsacus fullonum

Prickly heads; prolific seed spread

Photo: Isidre blanc · CC BY-SA 4.0 · Credits and sources

Creeping woodsorrel

Oxalis corniculata

Oxalate-containing plant; keep pets from grazing

Photo: Forest & Kim Starr · CC BY 3.0 · Credits and sources

Crownvetch

Securigera varia

Toxic to horses; spreading roots can smother vegetation

Photo: Dale Knox · CC0 1.0 · Credits and sources

Curly dock

Rumex crispus

Soluble oxalates; persistent roots and seeds

Photo: Ayotte, Gilles, 1948- · CC BY-SA 4.0 · Credits and sources

Dry oval teasel head on a prickly stalk, with rigid bracts surrounding the head.

Cutleaf teasel

Dipsacus laciniatus

Prickly stands can displace native vegetation

Photo: Alexander Klink · CC BY 3.0 · Credits and sources

Cypress spurge

Euphorbia cyparissias

Sap can injure skin and eyes

Photo: Tom Scavo · CC BY 4.0 · Credits and sources

Dalmatian toadflax

Linaria dalmatica

Spreads from roots; livestock concern

Photo: Walter Siegmund (talk) · CC BY-SA 4.0 · Credits and sources

Dame’s rocket

Hesperis matronalis

Escapes gardens and spreads

Photo: Anneli Salo · CC BY-SA 3.0 · Credits and sources

Diffuse knapweed

Centaurea diffusa

Skin irritation; tumbling seed spread

Photo: Kenraiz · CC BY-SA 4.0 · Credits and sources

Dyer’s woad

Isatis tinctoria

Persistent seed spread

Photo: Reuven Martin · CC0 1.0 · Credits and sources

Elongated mustard

Brassica elongata

Early detection priority in dry disturbed land

Photo: Dmitriy Bochkov · CC BY 4.0 · Credits and sources

A watermilfoil shoot at the water surface with a small flower spike rising above the water.

Eurasian watermilfoil

Myriophyllum spicatum

Fragments spread dense aquatic growth

Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org · CC BY 3.0 us · Credits and sources

Field bindweed

Convolvulus arvensis

Smothers plants; livestock concern

Photo: Svklimkin · CC BY-SA 4.0 · Credits and sources

Flowering rush

Butomus umbellatus

Small fragments spread aquatic colonies

Photo: Jacek Pietruszewski · CC BY 4.0 · Credits and sources

Giant knotweed

Reynoutria sachalinensis

Very persistent riparian colonies

Photo: Oleksandr Shynder · CC BY 4.0 · Credits and sources

Giant reed

Arundo donax

Dense stands displace riparian plants

Photo: zebedeugalinha · CC BY 4.0 · Credits and sources

Giant salvinia

Salvinia molesta

Floating mats harm aquatic habitat

Photo: Ixitixel · CC BY-SA 3.0 · Credits and sources

Green foxtail

Setaria viridis

Identify the grass behind the name “foxtail”

Photo: Petr Filippov · CC BY 3.0 · Credits and sources

Hairy willow-herb

Epilobium hirsutum

Spreads through wetland vegetation

Photo: Mathias keraudren · CC0 · Credits and sources

Halogeton

Halogeton glomeratus

Severe oxalate poisoning in livestock

Photo: Matt Lavin from Bozeman, Montana, USA · CC BY-SA 2.0 · Credits and sources

Henbit

Lamium amplexicaule

An early-flowering weed with useful nectar

Photo: Patrick Alexander from Las Cruces, NM · CC0 · Credits and sources

A dense patch of whitetop in bloom, with broad white flower clusters above green leaves.

Hoary cress

Lepidium draba

Spreading roots; possible livestock poisoning

Photo: Katrin Schneider / korina.info · CC BY-SA 4.0 · Credits and sources

Houndstongue

Cynoglossum officinale

Toxic to livestock

Photo: Bernd Haynold · CC BY 2.5 · Credits and sources

A pink-purple hybrid-knapweed head and several buds held beside branching stems; the source identifies this Littleton, Colorado plant as Centaurea × psammogena.

Spotted × diffuse knapweed hybrid

Centaurea × psammogena

Hybrid identification needs expert review

Photo: Tyler · CC0 1.0 · Credits and sources

Several fresh hybrid-toadflax shoots with variable, relatively broad leaves, photographed against a white background.

Yellow × Dalmatian toadflax hybrid

Linaria vulgaris × Linaria dalmatica

Variable hybrid; persistent spreading roots

Photo: Sharlene E. Sing, USDA Forest Service, Rocky Mountain Research Station · Public domain (U.S. federal employee work) · Credits and sources

Hydrilla

Hydrilla verticillata

Dense aquatic growth; wildlife disease association

Photo: Stanislav Murashkin · CC BY 4.0 · Credits and sources

Japanese knotweed

Reynoutria japonica

Root and stem fragments regrow

Photo: Michael Gasperl ( Migas ) · CC BY-SA 3.0 · Credits and sources

Jimsonweed

Datura stramonium

Serious poisoning risk to people and animals

Photo: H. Zell · CC BY-SA 3.0 · Credits and sources

Johnsongrass

Sorghum halepense

Livestock cyanide risk; added fire fuel

Photo: Jim Conrad · Public domain · Credits and sources

Jointed goatgrass

Aegilops cylindrica

Wheat-field and rangeland seed spread

Photo: Stefan.lefnaer · CC BY-SA 4.0 · Credits and sources

Kochia

Bassia scoparia

Tumbling seed spread; livestock poisoning risk

Photo: WildBoar · Public domain · Credits and sources

Large crabgrass

Digitaria sanguinalis

Fast seed production in thin lawns

Photo: Rasbak · CC BY-SA 3.0 · Credits and sources

Leafy spurge

Euphorbia esula

Irritating sap; eye injury risk

Photo: H. Zell · CC BY-SA 3.0 · Credits and sources

Mayweed chamomile

Anthemis cotula

Crop weed with unpleasant-smelling foliage

Photo: NY State IPM Program at Cornell University from New York, USA · CC BY 2.0 · Credits and sources

Meadow knapweed

Centaurea × moncktonii

Outcompetes pasture and meadow plants

Photo: Eric Coombs, Oregon Department of Agriculture, Bugwood.org · CC BY 3.0 us · Credits and sources

Mediterranean sage

Salvia aethiopis

Tumbles and spreads seed through rangeland

Photo: Stefan.lefnaer · CC BY-SA 4.0 · Credits and sources

Medusahead

Taeniatherum caput-medusae

Barbed awns; persistent fire-promoting thatch

Photo: Matt Lavin from Bozeman, Montana, USA · CC BY-SA 2.0 · Credits and sources

Moth mullein

Verbascum blattaria

Long-lived seeds sustain infestations

Photo: Stefan.lefnaer · CC BY-SA 4.0 · Credits and sources

Musk thistle

Carduus nutans

Sharp spines; competes with vegetation

Photo: Robert Flogaus-Faust · CC BY 4.0 · Credits and sources

Myrtle spurge

Euphorbia myrsinites

Poisonous · Eye & skin injury

Photo: Flocci Nivis · CC BY 4.0 · Credits and sources

Side view of yellow toadflax flowers and their long spurs beside developing reproductive structures, with a 10 mm scale.

Narrow-leaved Dalmatian toadflax

Linaria genistifolia

Listed taxon with difficult identification

Photo: Stefan.lefnaer · CC BY-SA 4.0 · Credits and sources

Orange hawkweed

Pilosella aurantiaca

Runners crowd lawns and mountain meadows

Photo: Tom Norton · CC BY 4.0 · Credits and sources

Oxeye daisy

Leucanthemum vulgare

Toxic to dogs and cats; dermatitis

Photo: Isidre blanc · CC BY-SA 4.0 · Credits and sources

Parrotfeather

Myriophyllum aquaticum

Aquatic mats obstruct waterways

Photo: Quillipede · CC0 1.0 · Credits and sources

Perennial pepperweed

Lepidium latifolium

Deep roots form persistent wetland colonies

Photo: Ayotte, Gilles, 1948- · CC BY-SA 4.0 · Credits and sources

Perennial sowthistle

Sonchus arvensis

Persistent underground spread

Photo: Gabriele Kothe-Heinrich · CC BY-SA 3.0 · Credits and sources

Plumeless thistle

Carduus acanthoides

Sharp spines; pasture competition

Photo: Dmitry Makeev · CC BY-SA 4.0 · Credits and sources

Poison hemlock

Conium maculatum

Poisonous to people & animals

Photo: Krzysztof Ziarnek, Kenraiz · CC BY-SA 4.0 · Credits and sources

Prickly lettuce

Lactuca serriola

Prickly leaves and prolific windborne seed

Photo: Teun Spaans (TeunSpaans) · Public domain · Credits and sources

Prickly sowthistle

Sonchus asper

Spiny leaves and rapid seed production

Photo: Didier Descouens · CC BY-SA 4.0 · Credits and sources

Prostrate knotweed

Polygonum aviculare

A mat-forming weed of compacted ground

Photo: Rasbak · CC BY-SA 3.0 · Credits and sources

Puncturevine / goathead

Tribulus terrestris

Sharp burs · Animal injury

Photo: Forest & Kim Starr · CC BY 3.0 · Credits and sources

Purple loosestrife

Lythrum salicaria

Crowds out wetland vegetation

Photo: Douglas Goldman · CC BY-SA 4.0 · Credits and sources

Quackgrass

Elymus repens

Rhizome fragments regrow in lawns and gardens

Photo: Rasbak · CC BY-SA 3.0 · Credits and sources

Redroot pigweed

Amaranthus retroflexus

Crop competition; nitrate and oxalate livestock risk

Photo: Lynk media · CC BY-SA 3.0 · Credits and sources

Redstem filaree

Erodium cicutarium

Seeds spread through lawns and pasture

Photo: Follavoine / follavoine.net · CC BY-SA 3.0 · Credits and sources

Rush skeletonweed

Chondrilla juncea

Deep roots and fragments sustain spread

Photo: Zihao Wang · CC BY 4.0 · Credits and sources

Russian knapweed

Rhaponticum repens

Toxic to horses

Photo: Amirh. absnd · CC0 · Credits and sources

Russian olive

Elaeagnus angustifolia

Thorns; riparian habitat concern

Photo: Georg Slickers · CC BY-SA 2.5 · Credits and sources

Russian thistle

Salsola tragus

Prickly tumbleweeds; livestock and fire hazards

Photo: Stefan.lefnaer · CC BY-SA 3.0 · Credits and sources

Scentless chamomile

Tripleurospermum inodorum

Prolific seeds; reported livestock irritation

Photo: Krzysztof Ziarnek, Kenraiz · CC BY-SA 4.0 · Credits and sources

Scotch thistle

Onopordum acanthium

Sharp spines; competes with vegetation

Photo: Krzysztof Ziarnek, Kenraiz · CC BY-SA 4.0 · Credits and sources

Shepherd’s purse

Capsella bursa-pastoris

An early-seeding lawn and garden weed

Photo: Rasbak · CC BY-SA 3.0 · Credits and sources

Siberian elm

Ulmus pumila

Numerous seedlings; weak branches

Photo: Shizhao · CC BY-SA 2.5 · Credits and sources

Spotted knapweed

Centaurea stoebe

Competes with native vegetation

Photo: Alan Vernon · CC BY 2.0 · Credits and sources

Squarrose knapweed

Centaurea virgata

Spiny seedheads; loss of rangeland forage

Photo: Alexander Dubynin · CC BY 4.0 · Credits and sources

A pale yellow, five-petaled sulphur-cinquefoil flower showing its central stamens.

Sulfur cinquefoil

Potentilla recta

Persistent pasture and roadside weed

Photo: Matt Lavin from Bozeman, Montana, USA · CC BY-SA 2.0 · Credits and sources

Meadow buttercup growing among grass, with yellow flowers held above deeply divided basal leaves.

Tall buttercup

Ranunculus acris

Fresh plant irritation and animal poisoning hazard

Photo: Daniel Cahen · CC BY 4.0 · Credits and sources

Tamarisk

Tamarix ramosissima

Alters riparian vegetation

Photo: Jerzy Opioła · CC BY-SA 3.0 · Credits and sources

Tansy ragwort

Jacobaea vulgaris

Poisonous to livestock; harmful alkaloids

Photo: jamie-aa · CC BY 4.0 · Credits and sources

Taurian thistle

Onopordum tauricum

Sharp spines; taxon listed as Scotch thistle

Photo: Louis Aureglia · CC BY 4.0 · Credits and sources

Tree of heaven

Ailanthus altissima

Root suckers form persistent thickets

Photo: Darkone · CC BY-SA 2.5 · Credits and sources

Tumble mustard

Sisymbrium altissimum

Another tumbleweed: brittle plants scatter persistent seed

Photo: Ben Keen · CC0 1.0 · Credits and sources

Velvetleaf

Abutilon theophrasti

Persistent seeds and strong crop competition

Photo: Salicyna · CC BY-SA 4.0 · Credits and sources

Ventenata

Ventenata dubia

Displaces forage and native grassland

Photo: Matt Lavin · CC BY 4.0 · Credits and sources

White clover

Trifolium repens

A spreading lawn plant with pollinator value

Photo: Ivar Leidus · CC BY-SA 4.0 · Credits and sources

White sweetclover

Melilotus albus

Moldy sweetclover hay can cause dangerous bleeding

Photo: zebedeugalinha · CC BY 4.0 · Credits and sources

Developing ribbed caraway fruits on the radiating stalks of a compound umbel.

Wild caraway

Carum carvi

Spreads by seed; pet safety concern

Photo: Ayotte, Gilles, 1948- · CC BY-SA 4.0 · Credits and sources

Wild carrot

Daucus carota

Do not confuse it with highly poisonous hemlocks

Photo: zebedeugalinha · CC BY 4.0 · Credits and sources

Wild parsnip

Pastinaca sativa

Sap plus sunlight can cause severe skin burns

Photo: Stefan.lefnaer · CC BY-SA 4.0 · Credits and sources

Wild proso millet

Panicum miliaceum

Seed contamination and crop competition

Photo: Kurt Stüber · CC BY-SA 3.0 · Credits and sources

Yellow flag iris

Iris pseudacorus

Ingestion concern; invasive wetland colonies

Photo: Kailey Alderfer · CC BY 4.0 · Credits and sources

Yellow nutsedge

Cyperus esculentus

Underground tubers sustain infestations

Photo: Krzysztof Ziarnek, Kenraiz · CC BY-SA 4.0 · Credits and sources

Yellow starthistle

Centaurea solstitialis

Severe horse poisoning; sharp spines

Photo: Юрий Данилевский (Yuriy Danilevsky) · CC BY 4.0 · Credits and sources

Yellow sweetclover

Melilotus officinalis

Moldy sweetclover hay can cause dangerous bleeding

Photo: Isidre blanc · CC BY-SA 4.0 · Credits and sources

Yellow toadflax

Linaria vulgaris

Spreads from roots; livestock concern