Description: Russian knapweed was introduced to North America from Asia. It is a perennial that reproduces by roots, rhizomes and seeds. It can grow up to 1m tall and young stems are covered with soft, short, grey hairs. The flowers are urn-shaped and pink to purple in colour, they occur singly at the ends of stems. The bracts underneath the flowers are green with papery edges. Flowers become straw-coloured at maturity.
Habitat & Impacts: Russian knapweed thrives in any soil, but does very well in clay. It is not tolerant of shade, drought or wet sites. It can invade rangelands and pastures, reducing carrying capacities and yields. Russian knapweed contains toxic compounds that cause a neurological disorder in horses if they consume large quantities. Method of Spread: Russian knapweed reproduces primarily through seed; however, it can re-grow from root and crown fragments. Seeds germinate throughout the growing season and plants typically flower from May to July. Seed is spread via humans, wind and animals and can remain viable in the soil for several years.
Location: Found in the south Cariboo, and is prevalent in southern BC.
Mechanical: Removal of the plant to ground level prevents seed production and repetition can help exhaust root reserves.
Chemical: Picloram, dicamba or a combination of clopyralid and 2,4-D are a few of the herbicides that effectively control Russian knapweed. (Ministry of Agriculture, Lands and Fisheries, 2002).
Biological: There is a gall-forming nematode and a rust fungus introduced in Alberta for biocontrol; these biocontrols have been introduced into BC, but have not established.
CCCIPC Priority & Treatment Strategy: Priority 1 (new invader).
Local Level – frequently mowing and hand pulling small infestations.
Landscape Level - chemical control and possible biological control for larger infestations.
Russian Knapweed flower head
Russian Knapweed plants
Invasive species profile taken from the Cariboo Chilcotin Coast Invasive Plant Committee Invasive Plant Regional Strategic Plan
Page last modified: March 15, 2017 09:36:29 PDT