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Federal Noxious Weed
TDA Noxious Weed
TPWD Prohibited Exotic Species
Invasive Plant Atlas of the US

NOTE: means species is on that list.

Centaurea stoebe ssp. micranthos


Spotted Knapweed

Synonym(s):
Family: Asteraceae (Aster family)
Duration and Habit: Biennial, Perennial Forb/Herb


Photographer: John M. Randall, The Nature Conservancy
Source: Bugwood.org

Description

Spotted knapweed is a biennial to perennial with sever branched upright stems growing from a sturdy taproot up to 5 feet in height. Deeply lobed, pale, grayish green leaves become smaller as they grow higher up the stem. Stems are slender and hairy, growing upright, stiff and branched. A single plant can have over 100 flower heads. Flowers are pink to purple and can occasionally be white, growing at the ends of the branches. Flower heads (excluding flowers are approximately 1/4 inch in diameter and 1/2 inch tall. Bracts are present around the flower head and have distinctive vertical veins below a black triangular shaped spot on the bract tip.

Ecological Threat: Spotted knapweed will dominate sites without management, lowering plant community diversity and decimating forage production. When well established, it can occupy over 95% of the available plant community.

Biology & Spread: This species rapidly colonizes disturbed areas, including overgrazed pastures and rangeland, but is capable of establishing and persisting in well-managed rangeland.

History: It is believed to have been introduced to the United States from Asia or Germany as a contaminate in alfalfa seed. It rapidly spread throughout the United States in rangeland and has become widespread in the west and Canada.

U.S. Habitat: This species rapidly colonizes disturbed areas, including overgrazed pastures and rangeland, but is capable of establishing and persisting in well-managed rangeland. Gravel pits, waste sites and rights-of-way are also suitable habitat.

Distribution

U.S. Nativity: Introduced to U.S.

Native Origin: Spotted knapweed is native to central, eastern and southeastern Europe.

U.S. Present: WA, OR, CA, AK, ID, MT, WY, NV, UT, AZ, CO, NM, ND, SD, NE, KS, LA, AR, MO, IA, MN, WI, MI, IL, IN, KY, TN, MS, AL, FL, SC, NC, VA, WV, OH, ME, VT, NH, NY, PA, MA, RI, CT, DE, MD

Distribution: Currently, this species has only been found at one location in Travis County, Texas.

Mapping

Invaders of Texas Map: Centaurea stoebe ssp. micranthos
EDDMapS: Centaurea stoebe ssp. micranthos
USDA Plants Texas County Map: Centaurea stoebe ssp. micranthos

Resembles/Alternatives

  • Centaurea americana (American basket-flower)
  • Management

    Prevention is the best management for spotted knapweed, always clean equipment, pets, boots and vehicles to prevent inadvertently moving seeds in the environment.

    Small infestations and single plants can be effectively managed by hand pulling or digging. If flower parts have formed, be sure to carefully bag and dispose of all parts when manually removing the species. Mowing is not effective, as the plant will flower and set seed below the mow level.

    For large or well established infestations, it is most effective to apply a selective, broadleaf herbicide prior to the plant flowering.

    USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS. MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.

    Text References

    Pacific Northwest Weed Management Handbook. 2014. Oregon State University.

    Online Resources

    Invasive Plant Atlas of the United States
    King County Noxious Weed Control Program

    Search Online

    Google Search: Centaurea stoebe ssp. micranthos
    Google Images: Centaurea stoebe ssp. micranthos
    NatureServe Explorer: Centaurea stoebe ssp. micranthos
    USDA Plants: Centaurea stoebe ssp. micranthos
    Invasive Plant Atlas of the United States: Centaurea stoebe ssp. micranthos
    Bugwood Network Images: Centaurea stoebe ssp. micranthos

    Last Updated: 2014-06-26 by JDB
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