Russian knapweed

(Acroptilon repens)

Introduced from Europe, Russian knapweed is a creeping perennial that reproduces by seed and creeping, horizontal roots. The ridged stems are stiff and 1 to 3 feet high, with thistle-like flowers that are lavender to white.

It 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 places. Russian knapweed is toxic to horses. It is most common in the Dry Hollow, Silt Mesa and Missouri Heights areas.