Russian knapweed
Rhaponticum repens (L.) Hidalgo
Synonym(s): hardheads

Russian knapweed is a perennial forb that can grow to 3 ft. (1 m) in height. Stems originate from a basal rosette of leaves. The rosette leaves can be unlobed to very lobed and are 2-4 in. (5-10 cm) long. Stem leaves are oblong, pinnately lobed to entire and up to 6 in. (15.2 cm) in length at the base of the stem and become smaller and less lobed toward the top. In summer to fall Russian knapweed produces flowers that are pink to purple and turn straw colored as they mature. The flower heads are approximately ½ in (1.2 cm) in diameter and urn shaped. Fruits (achenes) are ivory-colored with a tuft of hair that falls off at maturity. Russian knapweed is native to Eurasia and was introduced into the United States in the early 1900’s. This species can cause chewing disease in horses.

Identification, Biology, Control and Management Resources