Russian Knapweed

Russian knapweed (Acroptilon repens L.)

Russianknapweed is a member of the Aster family, Thistle tribe and is acreeping perennial introduced from Europe. It reproduces by seeds andcreeping, horizontal roots. Roots in the soil, may or may not be blackwith a scaly appearance. The rigid stems are erect, branched, and one tothree feet high. Young stems are covered with soft gray hairs or nap.

Theupper leaves are small and narrow with broken edges. Leaves attachedmidway up the stem have slightly toothed margins, while basal leaves aredeeply notched. The flowers are thistle-like, solitary, terminal, 1/3to 1/2 inch in diameter, lavender in color, or occasionally white. Theplant flowers in June to August and seed is produced from late summer toearly fall. Seed longevity is reported to be 2 to 3 years.

Russian knapweed is a serious noxious weed. It is very difficult tocontrol or eradicate once it becomes established, due to the 20 ft. deeproot system. It grows in cultivated fields, along ditch banks, fencerows, roadsides, and in waste places. It is distributed throughoutColorado, except in the eastern plains area. It is especially prevalenton the Western Slope mainly up to 8500 feet, but has been found growingas high as 11000 ft. It also tolerates 115 degree plus temperatures at2500 ft. in the desert near Tucson, Arizona. This weed is poisonous toany equine species; horses, mules and burros.

For more info and how to control, check out the La Plata County Weeds Dept. Fact Sheet

Russian knapweed infestation

Russian knapweed infestation

Russian knapweed coming out of asphalt

Russian knapweed bud

Russian knapweed flowers

Russian knapweed pre-bud infestation

Russian knapweed bud stage