brown knapweed USDA PLANTS Symbol: CEJA
U.S. Nativity: Exotic
Habit: Forbs/Herbs
Centaurea jacea L.

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Taxonomic Rank: Magnoliopsida: Asterales: Asteraceae
Synonym(s): brown knapweed
Native Range: Europe, n. Africa, n. & w. Asia (BAIL);

Appearance
Centaurea jacea is a perennial plant that grows 1-4 ft. (0.3-1.2 m) tall. The stems are ridged and may have purple stripes.
Foliage
The basal leaves are oblanceolate to elliptic and 2-10 in. (5 -25 cm) long. Leaves become smaller as they ascend the stem. These smaller leaves are lanceolate and attach directly to the stem.
Flowers
The brown bracts of the inflorescence give this plant its common name. Flowering occurs from June to October, when rose to purple flowers appear in 1-1.25 in. (2.5-3.2 cm) wide, solitary heads at the tips of the branches.
Fruit
Centaurea jacea produces small light brown, plumeless seeds; about 12 per head.
Ecological Threat
Centaurea jacea is an aggressive invader preferring moister, cooler conditions than other knapweed species. It can tolerate partial shade. It can invade grasslands, open woods, meadows, pastures, woodland clearings, and cutover areas of forest crowding out native plants or forage. Centaurea jacea is native to Europe.

Identification, Biology, Control and Management Resources

Selected Images from Invasive.orgView All Images at Invasive.org


Plant(s); in flower
Cindy Roche, , Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
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

Foliage;
Bruce Ackley, The Ohio State University, Bugwood.org
Additional Resolutions & Image Usage

Foliage; likely Centaurea nigra - black knapweed but may be hybrid with C. jacea (C. ×moncktonii syn. C. ×pratensis)
Rob Routledge, Sault College, Bugwood.org
Additional Resolutions & Image Usage

Flower(s); seedhead
Cindy Roche, , Bugwood.org
Additional Resolutions & Image Usage

Flower(s);
Bruce Ackley, The Ohio State University, Bugwood.org
Additional Resolutions & Image Usage

Flower(s);
Bruce Ackley, The Ohio State University, Bugwood.org
Additional Resolutions & Image Usage

Flower(s); likely Centaurea nigra - black knapweed but may be hybrid with C. jacea (C. ×moncktonii syn. C. ×pratensis)
Rob Routledge, Sault College, Bugwood.org
Additional Resolutions & Image Usage

Flower(s); likely Centaurea nigra - black knapweed but may be hybrid with C. jacea (C. ×moncktonii syn. C. ×pratensis)
Rob Routledge, Sault College, Bugwood.org
Additional Resolutions & Image Usage

Flower(s);
Bruce Ackley, The Ohio State University, Bugwood.org
Additional Resolutions & Image Usage

Seed(s);
Bruce Ackley, The Ohio State University, 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(s) Where Reported invasive.
Based on state level agency and organization lists of invasive plants from WeedUS database.

U.S. National Parks where reported invasive:
Blue Ridge Parkway (North Carolina)



Invasive Listing Sources:
Faith Campbell, 1998
Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
Mid-Atlantic Exotic Pest Plant Council, 2005
Pacific Northwest Exotic Pest Plant Council, 1998