Step 1. Correctly identify your thistle.
It is a perennial and had rhizomatous roots. It is the only rhizomatous thistle in Idaho or Wyoming. The plant is normally 2-3 feet tall.
It has deeply lobed leaves with small spines along the edges, leaves are smooth on top (no hairs). It has smooth stems between the leaves (no spiny wings).
It has light purple and occasionally white flowers, that are much smaller and more numerous than other thistles. Multiple flower heads to a stem.
Photo source: www.nps.gov/olym and https://www.nwcb.wa.gov/
Step 2. Choose your method.
Canada Thistle is a perennial species that initially establishes from seed but spread primarily by horizontal roots. It grows into very large dense patches.
Spot spray with an organic, burn down herbicide every 3-4 weeks throughout the growing season.
Step 3. Repeat.
Controlling Canada Thistle takes 2-8 seasons of vigilance and once it is knocked back, you will need to seed something else in its place.
To learn more about the biology of Field bindweed visit the web page below.