spotted knapweed: Centaurea stoebe (Asterales: Asteraceae): Invasive Plant Atlas of the United States

spotted knapweed	USDA PLANTS Symbol: CEST8 U.S. Nativity: Exotic Habit: Forbs/Herbs
Centaurea stoebe L.

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Taxonomic Rank: Magnoliopsida: Asterales: Asteraceae

Appearance: Centaurea stoebe is a bushy, winter-hardy, upright perennial forb living 3 - 5 years or sometimes longer, with a deep taproot.
Foliage: Rosette leaves bluish green, hairy and covered with shiny specks interspersed with translucent dots, 4-8 in. (10-20 cm) long. The size of the leaves decrease in size above the middle of the stem. They are alternate, spiraling and jutting out and upward. Basal leaves deeply divided into elliptic or linear lobes. Lobes become more slender and fewer on upper leaves.
Flowers: Flowers from June-November. Each branch topped by an egg-shaped flower bud covered with overlapping rows of dry, fringed green bracts with black tips. Bracts eventually part at top to allow a constricted pinkish-to-lavender thistle plume to radiate out and up, 0.75-1 in. (2-2.5 cm) wide and overall about 1 in. (2.5 cm) long.
Fruit: Fruits appear from June-February. Tightly packed seed heads of oblong, brownish, hairy nutlets (achenes), 0.1 in. (3 mm) long, topped by short stubby bristles. A thousand seeds can be produced per plant.
Ecological Threat: Centaurea stoebe rapidly colonizes roadsides and disturbed lands, especially dry sites. It can invade adjacent undisturbed prairies and open forests. A severe invasive species spreading into the South by seeds equipped for dispersal by wind, water, livestock, wildlife, and human activity, with viability in the soil for many years.

Selected Images from Invasive.org

View All Images at Invasive.org

Flower(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Plant(s); Bruce Ackley, The Ohio State University, Bugwood.org Additional Resolutions & Image Usage	Flower(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Flower(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage
Plant(s); Bruce Ackley, The Ohio State University, Bugwood.org Additional Resolutions & Image Usage	Flower(s); un-opened flower head Steven Katovich, , Bugwood.org Additional Resolutions & Image Usage	Root(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Foliage; Bruce Ackley, The Ohio State University, Bugwood.org Additional Resolutions & Image Usage
Foliage; Bruce Ackley, The Ohio State University, Bugwood.org Additional Resolutions & Image Usage	Stem(s); Bruce Ackley, The Ohio State University, Bugwood.org Additional Resolutions & Image Usage	Plant(s); Bruce Ackley, The Ohio State University, Bugwood.org Additional Resolutions & Image Usage	Plant(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage

EDDMapS Distribution:
This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org

State List
This map identifies those states that list this species on their invasive species list or law.

Invasive Listing Sources:

Pacific Northwest Exotic Pest Plant Council, 1998

Rhode Island Natural History Survey