Canada thistle is a noxious weed in Illinois. The Illinois Noxious Weed law mandates that each landowner controls the spread of and/or eradicates this plant from their land. This plant spreads by seed and vegetatively through creeping roots. The root system of this species is both widespread and deep (several feet deep). This makes management very difficult. It commonly grows in disturbed areas, forests, and prairies. It was introduced from Europe, but today can be found across most of the United States, excluding several states in the South. Canada thistle is able to quickly reproduce and create dense thickets. This can reduce the amount of space and nutrients available to nearby plants. It poses an economic threat to agricultural crops by reducing their yield.
As an alternative, spotted Joe-Pye weed is a plant with a similar appearance and size. There are a number of native and non-native species that could be used in place of Canada thistle. More desirable species may be found using the online Search Trees and Plants page of the Arboretum website. Before purchasing or planting, be sure to check for any local or state guidelines on this species, and ensure that this plant is suitable for its habitat by checking its attributes at mortonarb.org or plants.usda.gov.
- Family (English) Aster
- Family (botanic) Asteraceae
- Hardiness zones Zone 3, Zone 4, Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8
