A creeping forb that forms dense colonies from a deep spreading root system. Stems grow up to 4 feet and are erect and openly branched. It reproduces primarily by vegetative means, and can spread rapidly.
Rhizomatous perennial; stems and leaves hairy, lower leaves pinnately lobed, middle ones toothed, upper ones smooth margined, lower leaves not much larger than upper. Pink to purplish flower heads of disc only flowers, inner bracts densely hairy, pointed.
Habitat
Cultivated fields, orchards, pastures, and roadsides.
Flower Characteristics
Flower heads are solitary and at the tip of leafy branches. Bracts are pointed with papery tips. Flowers have a thistle-like appearance.
Leaf and Stem Characteristics
Lower leaves are 1-1/2 to 6 inches long and deeply lobed. Upper leaves are 1/2 to 2-3/4 inches, generally with smooth margins, but can be slightly lobed. Shoots and leaves are covered with dense gray hairs.
Fruit and Seed Characteristics
Achene bristles white, 1/4 to 1/2 inch long.
A single Russian knapweed plant can produce about 1,200 seeds per year.