Whitehall Biological Weed Control Project: Spotted Knapweed

Spotted knapweed (Centaurea stoebe) is one of the most widespread noxious weeds in Montana, occurring in all 56 counties. Spotted knapweed was probably originally brought to the United States through contaminated alfalfa shipments and discarded ballast soil from cargo ships.

This noxious weed arrived in America in the late 19th century and began appearing in Montana in the 1920s, where it has since spread across millions of acres statewide.

Spotted knapweed is a branched perennial with a deep taproot. They grow gray-green, woolly rosettes (rings of leaves at the base of the plant) with stems r...