Russian Knapweed · Acroptilon repens (L.) DC · is a
perennial Forb that originated in Eurasia. It flowers from June through
September, and reproduces through rhizomes and seeds. It was probably
introduced to North America in the late 1890s as a contaminant in crop
seed. It rapidly spread throughout much of the Great Plains.
Found in fields, pastures, rangeland, waste places, fence rows,
roadsides, and irrigation ditches. Russian knapweed is not grazed by
livestock because of its bitter taste. Deer rarely eat it.
Russian knapweed can be an aggressive and difficult to control
pest in alfalfa, clover, other forage crops, pastures, and occasionally
in row crops. It has become more abundant in recent years. It is a
noxious weed in many states.