Canada thistle is a long-lived perennial that reproduces by roots which is how it produces large dense patches. The goal of Canada thistle treatment is to starve the extensive root system. It will take several years of persistence.
Growth Habit – This perennial is heavily distributed throughout GVM. It grows 3′ tall and occurs in clumps or patches.
Flower – It is covered with 1/2″ to 3/4″ purple flowers.
Leaves – The leaves are prickly but not the stems.
Reproduction – It reproduces very little by seed and primarily by rootstock. Root systems may be several feet deep.
Management – These methods will ensure that no flowers will be produced and no seed set:
- Mow or clip plants as often as possible during the growing season
- It’s important to leave at least 9 leaves per stem (cut at a height of 8 inches or more to achieve)
- Bag and dispose of all clippings in order to minimize fire fuels. Dispose of in the GVM compactor
- If possible, apply herbicide in early October