Spotted knapweed grows well in dry sandy soils. Spotted knapweed grows 1-3 feet tall. It flowers from July to September. Its flowers are pinkish to purple and sit at the ends of branches.

Spotted knapweed (Centaurea maculosa ... Between July and September, it puts on a rogue show of thistle-shaped purple flowers that bob over black-mottled bracts — hence the name.

It is considered a threat to agriculture and the environment. “Spotted knapweed has attractive pink flowers, but it is not a good neighbor,” Friisoe said. “When it becomes established in an ...

Russian Knapweed (Rhaponticum repens) is a creeping perennial native to Eurasia. It was introduced into the U.S. as a ...