Weed Identification
Noxious Weeds?
In past newsletters, invasive plants have been highlighted. But there is a subset of these plants called “noxious weeds.” What is the difference? An invasive plant is any nonindigenous species whose introduction causes or is likely to cause economic or environmental harm or harm to human health.. There are both native and alien invasive plants. A noxious weed is one of only three plant species named specifically in Wisconsin statutes as requiring control. These are Canada thistle (Cirsium arvense), field bindweed (Convolvulus arvensis) and leafy spurge (Euphorbia esula).
Section 66.0407 states “A person owning, occupying or controlling land shall destroy all noxious weeds on the land,” and “The chairperson of each town . . . may annually on or before May 15 publish a class 2 notice, under chapter 985, that every person is required by law to destroy all noxious weeds, as defined in this section, on lands in the municipality which the person owns, occupies or controls.” The town chairperson also has the right to appoint one or more Weed Commissioners, whose duties are to enforce the statute. A weed commissioner investigates reports of noxious weeds, informs landowners of the requirement to destroy these weeds, or if the landowner does not comply, the weed commissioner causes the weeds to be destroyed. Landowners are billed for the removal on their property taxes.
In addition to noxious weeds, there are two “nuisance weeds” named in Wisconsin statue 23.235: purple loosestrife (Lythrum) and multiflora rose (Rosa multiflora). For these plants “no person may sell, offer for sale, distribute, plant or cultivate any nuisance weed or seeds thereof. Violators are fined up to $100 per offence.
– Christine Molling July, 2009
Please view most up to date legal document for invasive species.
Please view here for a listing of invasive species.
Every person is required by law to destroy all of the following noxious weeds growing on land in the Town of Berry, owned, operated, or controlled by that person:
Canada thistle
Leafy spurge
Buckthorn
Dames Rocket
Amur Honeysuckle
Garlic Mustard
Purple Loosestrife
Spotted Knapweed
Teasel
Wild Parsnip
Field bindweed (Creeping Jenny)
Herbaceous perennial, 2-6.5’ tall with upright, grooved stems that branch near top of plant. The stems are hairy.
Other names for this plant include:
- Common names: creeping thistle, field thistle, perennial thistle
- Scientific names: Carduus arvensis; Cirsium incanum
Ecological threat:
- Invades undisturbed areas such as prairies, savannas, glades, dunes, streambanks, sedge meadows, and forest openings. Also invades croplands, pastures, lawns, gardens, roadsides, ditches, and waste sites.
- Once it has established it spreads quickly, forming monocultures.
Classification in Wisconsin: Restricted
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for Canada thistle was based upon this literature review developed by the department.
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Leaves: Simple, alternate, lance-shaped, tapering, irregularly lobed, with spiny, toothed margins, stalkless. Green on both sides; smooth early but becoming pubescent with maturity.
Flowers: Numerous, small (0.5-0.75” wide), purple to pink (rarely white) terminal flower heads. Bracts have spineless tips. Blooms June-September.
Fruits & seeds: Small, light brown with a tuft of tan hairs loosely attached to the tip to enable wind dispersal. Seeds are often spread by mowing after flowering has begun.
Roots: Reproduces clonally by creeping roots that grow laterally in soil, up to 10-12’ per year. Also produces taproots that may grow more than 6’ deep. Readily regenerates from root fragments.
Similar species: Canada thistle is distinguished from all other thistles by creeping lateral roots, dense clonal growth; and small dioecious flower heads(meaning male and female flowers are produced on separate plants; however, it is difficult to distinguish the two flower types based on appearance).
Other invasive thistles include: European marsh thistle (Cirsium palustre) and Canada thistle (Cirsium arvense).
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Mechanical: Repeated pulling and mowing (minimum 3 times per growing season) weakens roots; mow when flower buds are formed, but have not yet opened. Late spring (May/June) burns for 3 consecutive years stimulates seed germination and kills seedlings. Later season burns are needed because early season burning can stimulate plant growth and flowering.
Chemical: Foliar spray glyphosate during the early bolting phase when plants are 6-10” tall, during the bud to flower phase, or rosettes in the fall; foliar spray with clopyralid or metsulfuron-methyl.
Biological: Stem weevil (Ceutorhynchus litura), bud weevil (Larinus planus), stem gall fly (Urophora cardui), and foliage feeder (Cassida rubiginosa).
For more information on control techniques, visit the Canada thistle factsheet by University of Wisconsin-Extension.
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Herbaceous perennial with deep root systems and milky sap in stems, flowers, and leaves. Sap is distasteful to some animals and can cause blistering on their mouths or throats. Leafy spurge grows to be 2-3’ tall.
Other names for this plant include:
- Common names: spurge, wolf’s milk
- Scientific names: E. esula ssp. esula; E. esula var. esula
Ecological threat:
- Invade open areas, including prairies, savannas, and roadsides. Can quickly create monocultures, excluding native vegetation and reducing wildlife habitat value.
- Tolerant of a wide range of habitats, from dry to moist and sunny to semi-shade. Most aggressive in areas where soil moisture is limited.
Classification in Wisconsin: Restricted
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for leafy spurge was based upon this literature review developed by the department.
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Leaves: Leaves are simple, alternate, bluish-green, smooth, and hairless with pointed tips.
Flowers: Small, yellowish-green, and surrounded by cup-shaped bracts. Flowers are paired, with 7-10 pairs clustered in umbels at tops of stems. Bloom late spring through mid-summer.
Fruits & seeds: Capsules contain 3 seeds each and burst when dry, dispersing seeds explosively. Each plant can produce more than 250 seeds. Seeds remain viable in the soil for up to 8 years. Dispersed by wildlife, humans, and water.
Roots: Extensive root system with taproots extending up to 15’ deep and lateral roots spreading up to 35’. New sprouts from root buds facilitate spread into undisturbed areas.
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Herbaceous perennial with deep root systems and milky sap in stems, flowers, and leaves. Sap is distasteful to some animals and can cause blistering on their mouths or throats. Leafy spurge grows to be 2-3’ tall.
Other names for this plant include:
- Common names: Carolina buckthorn, European buckthorn
Ecological threat:
- Invades oak forests, riparian woods, savannas, prairies, old fields, and roadsides. It thrives particularly on well-drained soils.
- Common buckthorn has a broad environmental tolerance. It leafs out very early and retains its leaves late into the growing season, giving them a longer growing season than native plants.
- Creates dense shade, eliminating regeneration of tree seedlings and understory species.
- Allelopathic; produces chemical compounds that inhibit the growth of other vegetation.
Classification in Wisconsin: Restricted
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for common buckthorn was based upon this literature review developed by the department.
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Leaves & stems: Ovate or elliptic, with prominent veins curving toward tip. Mostly opposite leaves, 1-2.5” long, with tiny teeth. Leaves remain on plants and stay green into fall. Bark is gray to brown with prominent light-colored lenticels. Cut bark exposes an orange inner cambium layer.
Flowers: Inconspicuous, small and clustered in leaf axils. Fragrant, greenish-yellow, 4-petaled flowers that bloom in spring.
Fruits & seeds: Abundant clusters of round, black, pea-sized fruit. Ripen on female plants in late summer. Dispersed by birds and mammals. Fruits remain on plants into winter after all the leaves have fallen.
Roots: Extensive, black fibrous root system.
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Mechanical:
- Small plants may be hand pulled. Prescribed fire for seedlings. Larger plants can be dug or pulled using a leverage tool such as a weed wrench.
- Girdling trees requires stripping the bark to expose the inner hardwood at a minimum of six inches. Effective any time of year.
Chemical:
- Cut-stump treatment with glyphosate in late fall
- Cut-stump or basal bark spray treatment around the stem with triclopyr ester in late fall through the winter.
For more information on control techniques, visit the Common buckthorn factsheet by University of Wisconsin-Extension.
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Showy, short-lived perennial or biennial, 3-4’ tall. Flowering stalks emerge in spring.
Other names for this plant include:
- Common names: dame’s-violet, mother-of-the-evening, sweet rocket. (Sometimes mistaken for the native wood phlox.)
Ecological threat:
- Invades moist and mesic woodlands, on woodland edges, and along roadsides, and in open areas.
- Dame’s rocket is thought by many to be a native wildflower and is found in wildflower seed mixes and planted as an ornamental
- It quickly escapes cultivation because of its prolific seed set.
Classification in Wisconsin: Restricted
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for dame’s rocket was based upon this literature review developed by the department.
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First year plants: Leaves form a basal rosette that overwinters.
Second year leaves: Lance-shaped, finely toothed, and alternate with short to no leaf stalk (sessile or with a very short petiole). Leaves decrease in size as they ascend the stem. Fine hairs on leaves and stems. Distinct light green midrib.
Flowers: 4-petaled flowers of white, pink, or purple color found on large, loose, rounded inflorescences. Fragrant, especially at night. Bloom late spring through summer.
Fruits & seeds: Abundant; produced in long, narrow seed pods (siliques), up to 5” long, that are constricted between seeds and break apart lengthwise at maturity.
Roots: Weak taproot.
Similar species: Native Phlox spp. have opposite leaves that are not toothed, and flowers with five petals, not four.
Garden phlox (Phlox paniculata; non-native) has opposite leaves that are not toothed, and flowers with five petals, not four. Blooms in late summer.
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Mechanical: Pull plants in early spring; plants in bloom should be bagged and disposed of in a landfill. Burn infested areas in seedling or rosette stage.
Chemical: Foliar spray with glyphosate or triclopyr on large infestations in late fall when native plants are dormant but the basal rosettes of dame’s rocket are still green.
For more information on control techniques, visit the Dame’s rocket factsheet by University of Wisconsin-Extension.
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Herbaceous perennial with deep root systems and milky sap in stems, flowers, and leaves. Sap is distasteful to some animals and can cause blistering on their mouths or throats. Leafy spurge grows to be 2-3’ tall.
Other names for this plant include:
- Common names: bush honeysuckle, late honeysuckle, Maak’s honeysuckle
Ecological threat:
- Thrives in forests, forest edges, and open grasslands forming dense stands.
- Plants leaf-out early and lose leaves late in the season which shade out native species and out-competes for nutrients.
- May be allelopathic – releases chemical compounds which inhibit the growth of other plants.
Classification in Wisconsin: Prohibited/Restricted (Restricted in Adams, Brown, Buffalo, Calumet, Columbia, Crawford, Dane, Dodge, Fond du Lac, Grant, Green, Green Lake, Iowa, Jefferson, Juneau, Kenosha, Kewaunee, La Crosse, Lafayette, Manitowoc, Marquette, Milwaukee, Monroe, Outagamie, Ozaukee, Racine, Richland, Rock, Sauk, Sheboygan, Vernon, Walworth, Washington, Waukesha, Waupaca, Waushara and Winnebago counties; Prohibited elsewhere)
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40.The recommendation for Amur honeysuckle was based upon this literature review developed by the department.
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Leaves: Dark green and elliptical to oblong. Leaves come to a long, sharp point and have hair along veins on the underside.
Flowers: Fragrant, white-pink flowers bloom in early spring (May-June), fading to yellow, and form in leaf axils. Flower stems are short and hairy.
Fruits & seeds: Bright red fruits in clusters of 2-4.
Roots: Shallow, fibrous roots.
Similar species: Bell’s honeysuckle; invasive (Lonicera x bella), Morrow’s honeysuckle; invasive (L. morrowii), and Tartarian honeysuckle; invasive (L. tatarica), are all very similar and equally invasive to Amur honeysuckle. Leaves on these Eurasian bush honeysuckles are more oblong, slightly hairy, and have a dull end. Flowers range from white – pink in color and also form in the leaf axils. Native bush honeysuckles (Diervilla lonicera) are smaller, have elongated fruit capsules, groups of 3-7 yellow flowers that turn reddish , and the stem has a solid pith. Fly-honeysuckles; native (Lonicera canadensis) also have red berries, but a solid stem pith, and white flowers that occur at the end of the branch (terminal) and hang down. Other native honeysuckles are woody vines that have connate (joined) terminal leaves below a cluster of flowers.
Herbaceous biennial with stems 2-4’ tall. First-year plants form a basal rosette that remains green through the winter. Second-year plants produce one to several flowering stems.
- Common names: mustard root, garlic root, garlicwort
- Scientific names: Alliaria officinalis; Alliaria alliaria; Arabis petiolata
- Invades high quality upland and floodplain forests and savannas, as well as disturbed areas, such as yards and roadsides. It is sometimes found in full sun, though most often grows in areas with some shade, and does not do well in acidic soils.
- Native herbaceous cover has been shown to decline at sites invaded by garlic mustard.
- Garlic mustard exudes antifungal chemicals into the soil that disrupt associations between mycorrhizal fungi and native plants, suppressing native plant growth.
Wetland perennial, 3’-7’ tall, with up to 50 stems topped with purple flower spikes. One main leader stem, but many side branches often make the plant look bushy. Clipped plants grow back, and cut stems readily re-root in soil to produce new plants. Many areas of the state use safe biocontrol beetles that feed on the loosestrife to keep it in check and allow other plants to grow.
Other names for this plant include:
- Common names: spiked loosestrife
- Scientific names: L. salicaria var. tomentosum; L. salicaria var. vulgare
Ecological threat:
- Prefers moist soils and shallow waters where it competes with native wetland plants. It will adjust to varying light conditions and water levels.
- Has been widely planted as an ornamental where it escapes to nearby water ways. It is still sold in nurseries as a sterile variety; however, it can still produce viable seeds with wild varieties.
Classification in Wisconsin: Restricted
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for purple loosestrife was based upon this literature review developed by the department.
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Herbaceous, short-lived perennial, 2-4’ tall. Persists as a rosette 1-4 years before bolting. Flowering plants usually have 1-6 stems, but many have up to 20.
Other names for this plant include:
- Scientific names: C. stoebe; C. stoebe ssp. micranthos; C. maculosa
Ecological threat:
- Invades dry areas, including prairie, oak and pine barrens, dunes, and sandy ridges. It also invades roadsides and disturbed areas.
- Roots exude allelopathic chemicals (compounds that inhibit the growth of other vegetation).
- It is not palatable as a forage plant and is avoided by both livestock and native grazers.
- Infestations cause increased runoff, sedimentation, and decreased water-holding capacity in soil.
Classification in Wisconsin: Restricted
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for spotted knapweed was based upon this literature review developed by the department.
CAUTION: Wear long sleeves and gloves when handling. Spotted knapweed exposure can irritate skin.
Leaves: Gray-green, covered in rough hairs, and deeply divided. Rosette leaves grow up to 6” long. Stem leaves alternate, with lower stem leaves resembling rosette leaves, becoming small (1-3” long), entire, and linear higher up the stem.
Flowers: Thistle-like, pink to purple flower heads, rarely white. Flower heads have stiff bracts tipped with black, fringed hairs. Bloom min-summer to early fall.
Fruits & seeds: Wind-dispersed for short distances but carried long distances by humans, livestock, or rodents. Viable in soil for up to 7 years.
Roots: Strong taproot. Some plants produce a shallow mat of fibrous roots extending from plant for several feet. Some sprouting from lateral roots occurs.
Similar species: There are several non-native Centaurea species that look similar. Spotted knapweed can be distinguished by the bracts on the flower head that are tipped with black.
Mechanical: Small infestations can be repeatedly hand pulled making sure to remove entire root. Continual mowing as close to the ground as possible, prior to seed-set, may suppress populations.
Chemical: Foliar spray of glyphosate, clopyralid, or aminopyralid and a non-ionic surfactant during bolting or flower bud stage.
Biological: There are currently 13 biological control agents. Successful treatment requires one seed head and one root mining agent. Contact the Wisconsin Department of Agriculture, Trade and Consumer Protection.
For more information on control techniques, visit the Spotted knapweed factsheet by University of Wisconsin-Extension.
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Herbaceous, monocarpic perennial. Grows as a basal rosette for at least one year. Forms a prickly, angled flowering stalk, 2-6’ tall, typically in second or third year.
Other names for this plant include:
- Common names: Fuller’s teasel, wild teasel
- Scientific names: D. fullonum ssp. fullonum; D. fullonum ssp. slyvestris; D. sylvestris
Ecological threat:
- Invades open areas, prairies, savannas, and sedge meadows, as well as roadsides and disturbed areas.
- Rapid range expansion of cut-leaved teasel has been observed in several Midwestern states.
Classification in Wisconsin: Restricted
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for common teasel was based upon this literature review developed by the department.
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Leaves: Opposite, large (up to 1.5’ long), oblong, and prickly. Leaves of flowering plants join into cup around stem. Common teasel’s leaves are not lobed.
Flowers: Hundreds of small flowers, clustered in dense, egg-shaped heads. Stiff, spiny, leaf-like bracts curve up from base of flower head. Common teasel has purple flowers and bracts longer than the flower heads. Common blooms from June-October.
Fruits & seeds: Each plant can produce as many as 2,000 seeds. Seeds remain viable in the soil for at least 2 years.
Roots: Deep taproot, up to 2’ long and 1” in diameter
Similar species: Cut-leaved teasel (Dipsacus laciniatus) leaves are broader and have deep, feathering lobes. Its bracts are shorter than the flower heads. The flowers are white and bloom from July-September.
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CAUTION:
Care should be taken to avoid skin contact with the juices of this plant. Proper clothing (gloves and a long-sleeved shirt) must be worn to prevent the phytophotodermatitic effects.
Herbaceous, monocarpic perennial. Grows as a basal rosette for at least one year. Forms a prickly, angled flowering stalk, 2-6’ tall, typically in second or third year.
- Common names: parnsip
- Scientific names: P. sativa var. pratensis
- Invades prairies, oak savannas, and fens as well as roadsides, old fields, and pastures.
- Broad habitat tolerance; grows in dry, mesic, or wet habitats, but it does not grow in shaded areas.
Herbaceous perennial with deep root systems and milky sap in stems, flowers, and leaves. Sap is distasteful to some animals and can cause blistering on their mouths or throats. Leafy spurge grows to be 2-3’ tall.
Field bindweed is difficult to eradicate because the seeds remain viable in soil for up to 20 years. One plant can produce up to 500 seeds. The deep, extensive root system stores carbohydrates and proteins and allows it to sprout repeatedly from fragments and rhizomes following removal of aboveground growth.
Attribution for this image goes to Elizabeth J. Czarapata
Control and treatment methods can be found here for Field Bindweed
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