Spotted knapweed has been reported in many areas of the province, especially ones with lots of vehicle traffic. Calgary, major highways, and border crossings are just a few areas with high densities of this prohibited noxious weed.
The plant skeletons get caught in vehicle undercarriages, contributing to its spread. It also thrives in disturbed sites with little to no shade and can tolerate poor soil and moisture conditions. Infestations are often found in gravel pits, roadside ditches, and rangeland.
A single spotted knapweed plant can produce up to 140,000 seeds per year and they can remain viable for up to a decade. It also has another trick — its roots release a chemical that inhibits the growth of other plants, allowing it to quickly displace native species and forages. It takes years to eliminate an infestation.
It has a pinkish-purple flower with black-tipped (spotted-looking) bracts at the base of the flower. Contact your local Agricultural Fieldman if you think you’ve seen this nasty invader.