It has a beautiful yellow showy flower, but do not let that fool you — Bighead Knapweed is highly invasive.
This invader is a long-lived perennial native in eastern Europe. It produces an abundance of seeds, which have bristles that can easily attach to animal fur. It can be found in flower beds throughout Alberta.
Bighead Knapweed flowers from July to September, and can grow 50 to 170 centimetres tall. It has a large tap root that becomes hardier with age. The leaves are lance shaped and 10 to 30 centimetres long with slightly pointed tips. Leaf margins are smooth, covered with short fine hairs, and dotted with resin glands. Bighead Knapweed is the largest variety in the knapweed family.
Many infestations result from garden or flower bed escapes. That is why it should not be grown as an ornamental.
Bighead Knapweed is listed as a prohibited noxious weed under the Alberta Weed Control Act. Local authorities, such as your local agricultural fieldman, must be notified if it is found.
By Tori Cherniawsky, Agricultural Fieldman, Smoky Lake County