Alternate name: Russian Knapweed
Family: Asteraceae, Aster view all from this family
Description Introduced. An invasive, much-branched, upright-growing weed that spreads by black creeping roots.
Flowers: scaled buds open to reveal whitish to rose-pink, thistle-like flower heads at the tips of stems.
Leaves: variable, copious, gray-green; stem leaves small, narrow, toothed.
Height: 1-3' (30-90 cm).
Warning Plant parts are reported to be poisonous to horses when eaten. Humans should avoid consuming plants that are toxic to animals.
Habitat Grasslands, agricultural fields, scrub or shrub habitats, riverside communities, roadsides, ditches, and other disturbed habitats.
Range Asia native; naturalized in North America from the West Coast eastward to Manitoba, Ohio, Kentucky, Arkansas, and Texas; recently reported in Virginia.
Discussion Accidentally introduced to the United States as a contaminant in crop seed, Hardheads, or Russian Knapweed, is classified as a noxious weed in dozens of states and four Canadian provinces. Budding root systems enable this plant to spread rapidly; toxic compounds exuded by the plant make the soil inhospitable for other plants. It is thus able to infiltrate natural habitats and outcompete native flora.