State Designated Noxious Weeds

Common Mullein
Black Henbane
Canada Thistle
Common Burdock
Diffuse Knapweed
Common St. Johns Wort
To learn more about County Declared Noxious Weeds, visit website for each county.

2019 State Designated Species 2019 County Declared Species List

Common Mullein


• Verbascum Thapsus is a tap-rooted biennial forb in Scrophulariaceae (Figwort) family
• Yellow, 5-petaled flowers born on large terminal spikes
• Large, densely wooly leaves narrow towards the apex of the plant
• Can grow to be 10 feet tall but more commonly found in the 2-6 foot range
• Invasive in disturbed soils and on well-drained rocky soils.

Black Henbane


• Hyoscyamus niger is a tap-rooted annual or biennial forb in the Solanaceae (Nightshade) family
• Unusual flowers are brownish yellow with distinct purple veins and a purple-to-black center
• Large hairy leaves with irregularly lobed margins and distinct light-colored midribs and veins
• Foliage produces a foul odor and has a ‘greasy’ or oily appearance
• The entire plant is toxic
• Invades disturbed soils and waste areas

Canada Thistle


• Cirsium arvense is a creeping perennial forb in the Asteraceae (Sunflower) family
• Flowers are small, range from dark pink to white in color, and are dioecious, meaning either male or female
• Leaves vary from plant to plant, but most have deeply incised, spiny and toothed margines and smooth to slightly hairy surfaces
• Reproduces primarily from extensive underground root system but may reproduce from seed if male and female plants are present
• One of the most invasive species ever introduced, Canada thistle successfully invades fields, rangelands, turf, roadsides, riparian areas, and many other places with a vast variety of environmental conditions.



• Centaurea diffusa is a tap-rooted perennial forb in the Asteraceae (Sunflower) family
• Solitary flowers range from pink to white and are subtended by spiny bracts
• Leaves are greyish-green, alternate, and rough to the touch
• Diffuse knapweed invades pastures, riparian areas, roadsides, and waste areas. It is a tough competitor on dry sites and rapidly invades and dominates disturbed areas. 

Common Burdock


• Articum minus is a large tap-rooted biennial forb in the Asteraceae (Sunflower) family
• Flowers are bright pink to purple, resemble thistle flowers, and produce seeds inside of Velcro-like burs
• Large, spade-shaped basal leaves resemble Rhubarb, but upper leaves are smaller and ovular. Both are dull green above and greyish underneath
• Thrives in shade and moist, fertile soils

Common St. Johns Wort


• Hypericum perforatum is a perennial forb that spreads by seeds or creeping roots
• Bright-yellow, five-petaled flowers are ½”- ¾” in diameter and can have over a dozen stamens
• Leaves are covered with small glands that resemble pinholes when held up to a light source. The glands produce photoactive oil that can cause rashes or blisters in animals when browsed
• Typically invades gravelly, well-drained soils and slopes with moderate amounts of sunlight

Common Tansy


• Tanacetum vulgare is a fibrous-rooted bushy perennial plant in the Asteraceae (Sunflower) family
• Dense, flat-topped clusters of yellow button-like flowers that lack petals
• Leaves are aromatic and fern-like, and divided into toothed leaflets
• Stems are reddish-brown and become woody towards the base of the plant
• Tansy has a history of medicinal use and can be toxic if consumed in large quantities
• Readily invades riparian areas

Dalmation Toadflax


• Linaria dalmatica is a creeping perennial forb in the Scrophulariaceae (Figwort) family
• Yellow, snapdragon-like flowers with orange centers
• Blueish-green, waxy leaves with clasping bases alternate up the stem
• Reproduces from prolific, long-lived seeds and from creeping rootstocks, making it difficult to control
• Invades disturbed rocky soils and establishes monocultures on south-facing slopes

Dyer’s Woad


• Isatis tinctoria is a tap-rooted biennial or perennial forb in the Brassicaceae (Mustard) family
• Clusters of tiny, yellow 4-petaled flowers born in clusters at the top of the plant
• Leaves are long, narrow, and simple with prominent white veins
• Seeds are contained in black, papery seed pods that hang from branches like ornaments
• Dyer’s woad was likely introduced into the U.S. during the 1700’s for its use in producing a blue textile dye

Field Bindweed


• Convolvulus arvensis is a prostrate or climbing perennial vine in the Convulvulaceae (Morning Glory) family
• Flowers are funnel-shaped, pale pink to white, and subtended by two small bracts
• Leaves are alternate, simple, and shaped like arrow-heads
• Root system includes extensive creeping rhizomes, making this plant impossible to remove mechanically
• Seeds may be viable in the soil for over 60 years which, when combined with its extensive root system, make it one of the most challenging noxious weeds to control

Hoary Cress (Whitetop)


• Lepidium draba is a short-statured creeping perennial forb in the Brassicaceae (Mustard) family
• White 4-petaled flowers in dense, flat-topped clusters at top of plant
• Leaves are alternate, greyish-green and lance-shaped with clasping leaf bases
• Reproduces both from prolific seed production and creeping rhizomes
• One of the first noxious weeds to flower in the spring (April-May), and is best treated in the bud stage



• Cynoglossum officinale is a tap-rooted biennial forb in the Boraginaceae (Borage) family
• Flowers are reddish-purple, 5-petaled, and emerge along wiry stalks
• Seeds are enclosed in burs that readily stick to anything passing too close
• Leaves are large, pointed at the tip, and covered with soft white hairs
• Plant contains toxic alkaloids and is poisonous to livestock

Leafy Spurge


• Euphorbia esula is a creeping perennial forb in the Euphorbiaceae family
• Deep, spreading roots often exceed 20 feet in depth, and can regenerate new buds if plant is pulled, mowed, burned, or cut
• Tiny, inconspicuous flowers are enclosed by yellowish-green, heart-shaped paired leaves that resemble flower petals
• Seed capsules explode, shooting seeds up to 15 feet
• Alternate leaves are long and narrow
• Contains a milky latex which can cause blisters and rashes if it contacts the skin or blindness if it contacts the eyes and is poisonous to cattle and wildlife.

Musk Thistle


• Carduus nutans is a tap-rooted biennial forb in the Asteraceae (Sunflower) family
• Bright purple flowers are up to 3 inches across, solitary, nodding, and subtended by broad, pointed bracts
• Dark green leaves with light-colored margins are deeply lobed, hairless, and have spiny margins
• Seeds can be in excess of 20,000 per plant and are viable for up to 10 years in the soil

Oxeye Daisy


• Chrysanthemum leucanthemum is a fibrous-rooted perennial forb in the Asteraceae (Sunflower) family
• Solitary flowers have a yellow central disk with many white ray petals and resemble common daisies
• Basal leaves are spoon-shaped and have lobed margins. Leaves get progressively narrower and smaller as they move up the stem
• It is not grazed by livestock or wildlife due to a disagreeable odor and taste, which allow it to aggressively invade native grasslands and displace valuable forage
• Beware of this invader in ornamental plantings and “wildflower seed” mixes

Perennial Pepperweed


• Lepidium latifolium is a creeping perennial in the Brassicaceae (Mustard) family
• Tiny, white, 4-petaled flowers in dense clusters near the top of the plant
• Leaves are alternate, lance-shaped and waxy with smooth to toothed margins and get smaller from base to apex of plant
• Reproduces from seed as well as deep-seated, spreading rootstocks
• Robust, often woody stems can reach 4 feet in height
• Invader of riparian areas, pastures, roadsides and disturbed areas

Perennial Sowthistle


• Sonchus arvensis is a creeping perennial in the Asteraceae (Sunflower) family
• Flowerheads are yellow composites of disk and ray florets and resemble dandelions
• Leaves are narrow, alternate, and have prickly serrations of their margins. Lower leaves are crowded together, while upper leaves are sparser and have bases that clasp the stem
• Reproduces by creeping roots as well as wind-dispersed seeds
• Tissue produces milky sap when broken

Plumeless Thistle


• Carduus acanthoides is a tap-rooted biennial forb in the Asteraceae (Sunflower) family
• Flowers are bright pink, smaller than musk thistle flowers, erect, and subtended by many narrow, spiny bracts
• Leaves are deeply serrated and have hairy undersides
• The stems have distinct spiny ridges running all the way up to the flower heads

Purple Loosestrife


• Lythrum salicaria is a tall (up to 8 feet), bushy perennial forb in the Lythraceae (Loosestrife) family
• Purple flowers born on long, vertical racemes have 5-7 petals and numerous stamens
• Leaves are simple, lance-shaped, have smooth margins, and are arranged in opposite or whorled orientation along square stems
• Leaves and stems resemble plants in the Mint family, but flowers distinguish it from other mints
• Highly invasive in riparian areas, wetlands, and irrigation canals and ditches where it can impede water flow



• Agropyron repens is a creeping perennial grass in the Poaceae family
• Reproduces both from seeds and from creeping yellowish-white rhizomes that are sharp-pointed and able to penetrate hard soils, tubers and roots of other plants
• Leaves have auricles, are covered with soft hairs, have a 0.5 mm ligule, and often show a small constriction near the point of the leaf
• A flattened spike up to 10 inches long is composed of two rows of spikelets which contain seeds that have short, straight awns or lack awns altogether

Russian Knapweed


• Acroptilon repens is a creeping perennial forb in the Asteraceae (Sunflower) family
• Flowers are pink-to-purple, solitary, terminal, 1/3 to 1/2 inch in diameter and have paper-like bracts
• Upper leaves are small and narrow with broken edges; leaves midway up the stem have slightly toothed margins, while basal leaves are deeply notched
• Leaves and stems are covered with short, stiff hairs
• Reproduces both by seed and by aggressive, creeping, lateral roots that are black and scaly
• Invades cultivated fields, ditch banks, fence rows, roadsides, and waste areas. The plant is very poisonous to horses

Russian Olive


• Elaeagnus angustifolia is a perennial deciduous tree or shrub in the Elaeagnaceae family
• Clusters of small, yellow, fragrant flowers produce small olive-shaped fruits that are protected by 2-inch thorns
• Long, narrow, silvery, aromatic leaves covered with scaly pubescence
• Reddish-brown stems and flexible twigs coated with gray pubescence
• Reproduces from seed and lateral roots that spread from a central taproot
• Forms dense, impenetrable stands in river corridors, choking out native vegetation



• Tamarix ramosissima is a deeply-rooted, partially deciduous evergreen tree or shrub in the Tamaricaceae family
• Tiny, pink to white, 5-petaled flowers grow along branched inflorescences at terminus of branches
• Leaves are small and scale-like, resembling true cedars, and exude a salty residue that collects of foliage
• Numerous slender, upright, and highly branched stems with smooth, reddish-brown bark
• Reproduces through prolific production of small, wind-dispersed seeds
• In addition to releasing salts into the soil this plant can transpire up to 200 gallons of water a day, potentially impacting soil moisture and alkalinity

Scotch Thistle


• Onopordum acanthium is a tap-rooted biennial forb in the Asteraceae (Sunflower) family
• Reddish-purple flowers are 1-2 inches in diameter and subtended by narrow, spine-tipped bracts
• Velvety-gray leaves are large, coarsely lobed, hairy on both sides, and have conspicuous spines lining their margins
• Spiny wings emanating from leaves extend along erect, branching stems
• Reaching heights of 12 feet, this aggressive invader forms stands so thick they are impenetrable to livestock and recreationists.

Skeletonleaf Bursage


• Ambrosia tomentosa is a bushy creeping perennial in the Asteraceae (Sunflower) family
• Both male and female flowers are found on a single plant – yellow male flowers are clustered on elongated branches, and pairs of tiny, green female flowers form in leaf axils below
• Alternate leaves are smooth above and fuzzy on the underside, oval to lance-shaped, and deeply segmented with coarsely-toothed margins
• Reproduces both by creeping rootstocks and seeds, which are found in brown, spiny burs
• This plant is native to the Great Plains region, but listed as a noxious weed due to its potential to contaminate wool production and cause severe allergies.

Spotted Knapweed


• Centaurea stoebe is a weakly tap-rooted biennial or short-lived perennial forb in the Asteraceae (Sunflower) family
• Solitary pink flowers form on branch tips and are sub-tended by black-tipped bracts that distinguish it from other knapweed species and earn its name
• Green leaves are covered with fine hair that give the plant a silvery appearance. Leave are long and deeply lobed below and short and narrow above
• This very aggressive invader infests large areas quickly, displacing native plant communities and offering very little big game or livestock forage value

Yellow Toadflax


• Linaria vulgaris is a creeping perennial forb in the Scrophulariaceae (Snapdragon) family
• Its yellow-orange snapdragon type flowers resemble those of Dalmatian toadflax
• Numerous long, narrow, smooth and pointed leaves alternate up the stem
• Reproduces through seeds and vigorous, woody roots
• This extremely adaptable invader can move into established native plant communities and form dense monocultures.



• Taeniatherum caput-medusa is a winter annual grass in the poaceae family that flowers in May and June
• Inflorescence is a spike with very long awns making it nearly as wide as it is long. Each spikelet has minute barbs and 4-inch twisted awns at maturity.
• Leaf blades are 1/8 inch wide, rolled, and slightly hairy
• Bristly seed heads persist through winter



• Ventenata dubia is a slender, erect annual grass in the Poaceae family
• Inflorescence is an open panicle with slender, spreading branches, typically at 90 degree angles to the raceme, bearing spikelets at their tips. Awns are up to 1-inch long
• Thin branching stems are naked and wiry, making the grass hard to cut, and earning it the common name “wire grass”
• Aggressive invader of rangeland and disturbed sites but also found in grain crops.

Yellow Starthistle


• Centaurea solstitialis is a tap-rooted annual forb in the Asteraceae (Sunflower) family
• Yellow solitary flowers have stiff, 1-inch spines protruding from their involucre
• Basal leaves are deeply lobed, upper leaves are small and sharply pointed, and leaves and stem are covered with cottony fiber