Russian knapweed (Acroptilon repens) is a non-native deep-rooted perennial that spreads by aggressive, creeping, horizontal roots (rhizomes) and seeds. The roots are black with a scaly appearance. Russian knapweed can grow up to 3 feet in height. The stems and leaves are covered with short, stiff hairs. The flowers are urn-shaped, pink to purple in color, and are solitary at the tips of the upper branches. Russian knapweed can be distinguished from other knapweeds by the pointed papery tips of the rounded bracts that surround the flowers. Russian knapweed emerges in early spring after soil temperatures remain above freezing. It produces flowers from June to August and sets seed in late summer to early fall. Russian knapweed reproduces primarily from its root system. Buds on the horizontal roots can form adventitious shoots that can grow to be independent plants.
Russian knapweed Fact Sheet