Rhaponticum repens, Centaurea repens, or Acroptilon repens L.
Russian knapweed is a creeping perennial introduced from Europe. It reproduces by seeds and very aggressive creeping, lateral roots. The roots are both vertical and horizontal in the soil and are generally black with a scaly appearance. The ridged stems are erect, rather stiff, branched, and one-to-three feet tall. Young stems are covered with soft gray hairs or knap. The upper leaves are small and narrow with broken edges; leaves midway up the stem have slightly toothed margins, while basal leaves are deeply notched. The flowers are pink-to-purple, solitary, terminal, 1/3 to 1/2 inch in diameter and have paper-like bracts. It flowers from July to September.
Russian knapweed is an aggressive noxious weed and is very difficult to control or eradicate once it becomes established. It grows in cultivated fields, along ditch banks, fence rows, roadsides, and in waste areas. The roots can reach depths of over 8 feet and the plant is also very poisonous to horses. Teton County currently has very few infestations of Russian knapweed, but it is a serious problem for our Fremont County neighbors.
If you find this weed on your property or around Teton County, please report it immediately at 733-8419.
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