Russian Knapweed is a flowering, bushy perennial weed in the daisy family and native to Eastern Europe, Mongolia, and the Himalayas. The plant has deep roots and a reputation for long life (some stands are reported to have been in existence for 75 years). The roots spread and the plant will form dense colonies. The leaves and stems are initially covered in long, fine hairs, but become smooth with age. Pink to purple flowers appear in spring and last through summer. Russian Knapweed is considered a serious weed pest in the western United States. It reproduces both by seeds and by adventitious buds on deep, spreading roots forming dense colonies and is difficult to control or eradicate once it becomes established. It is poisonous to horses. Disease, Insect Pests, and Other Plant Problems: No known diseases or insect pests. Russian Knapweed is persistent and difficult and expensive to control, is toxic to horses and out competes native vegetation. It is listed by western states as a noxious weed, to be suppressed, contained, or locally extirpated.
Curated pairwise relationships between this plant and others in the library — who feeds
whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.
No curated interactions recorded for this species yet.
Also noted by NC State
Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell
apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.
Basal rosette of leaves 2 to 4 inches, lobed or unlobed. Stem leaves are oblong, pinnately lobed to entire and up to 6 inches long. They get smaller and less lobed toward the top of the stem.
Flower color
Pink; Purple/Lavender
Flower form
Head
Flower shape
Urn
Flower size
< 1 inch
Flower detail
Pink to purple blooms from summer through fall, as they mature they turn a straw color. The 1/2 inch head-inflorecese is urn-shaped.
Bloom time
Fall; Summer
Fruit color
Cream/Tan
Fruit type
Achene
Fruit detail
Ivory colred achene with tufts of hair that fall off as fruits mature.
Stem color
Green
Stem detail
Stems have long, tangled hairs but become smooth and green with age.
Wildlife & Ecology
Native status
Non-native
Origin
Eastern Europe to Mongolia
Distribution
Introduced to Northern Europe, most of the United States (except the Southeast), Canada, Australia, and South Africa.
Food & Medicine
Harvest time
Fall
Fruit type
Achene
Edibility
Can be poisonous to horses.
Landscape Use
Garden tags
#perennial weed #non-toxic for cats #problem for horses #non-toxic for dogs #weedy #rhizomatous #bushy #spreading #Noxious Weed (state list)