Nodding Thistle (Carduus nutans L. spp. leiophyllis (Petrovic))
It is a biennial forb with single, large reddish-purple flowers (up to 5cm) that nod. It is originally from Eurasia and North Africa. They grow up to 2.4m tall with spiny, deeply lobed alternate leaves. The leaves are dark green and the margins can be white. It has a fleshy taproot.
LRISS Category: CONTAIN
Habitat & Ecology
Nodding thistle reproduces by seed only and each plant can produce up to 100,000 seeds. The seeds can last in the soil for up to 10 years. Wind, water, wildlife and livestock spread the seed. It is found along roadsides and disturbed habitat.
It can invade pastures but it is unpalatable to livestock. It competes with native plants and spreads aggressively in disturbed areas forming dense patches.
There are 3 bioagents (natural enemy in native ecosystem) that has been released to manage infestations: 2 weevils and a fly. Mechanical treatment must remove the entire crown before it sets seed to ensure it does not re-grow. Minimize disturbance to prevent infestations. Contact LRISS for more management information.
Province of British Columbia. 2002. A Guide to Weeds in British Columbia.