Canada Thistle

Cirsium arvense

Characteristics

Canada thistle, a terrestrial herbaceous perennial in the Asteraceae family, is an open-land invasive that prefers disturbed upland areas as well as wet areas with water fluctuations. Canada thistle can be found in clay to gravelly soils.

• typically grows 3-5 feet tall
• stalk-less leaves around 6 inches long, wavy, lobed leaves with yellow spines at each lobe
• stem is spineless, unlike the leaves and unlike bull thistle and European marsh thistle
• pink, white, or lavender-colored flowers with flat bracts and pointed tips that bloom in June
• seed are fluffy, white tufts of hair that are wind dispersed

Note: Another key characteristic of Canada thistle is the fuzzy underside of the leaves.

For more information visit Midwest Invasive Species Information Network (MISIN).

KISMA Management Practices

Canada thistle forms extremely extensive root systems that need to be repeatedly damaged to keep them from growing back. These root systems can spread very aggressively and can expand from 6 feet wide to 10 feet wide in one growing season.

1. annually hand pull or dig rosettes and adult plants, dry in the sun or bag for landfill
2. if thistle has bloomed, clip off all flowers, buds, and seedhead
3. be sure to collect these flower, bud, and seedhead clippings in a bag and dispose of in a landfill

Note: It is important to hand pull plants repeatedly to eventually exhaust the seed source and deplete populations. It is also important when disposing of clippings to not spread them anywhere else, as they will seed wherever they can.

Native Alternatives

Species such as native swamp thistle (Cirsium muticum), swamp milkweed (Asclepias incarnata), and joe-pye weeds (Eutrochium maculatum) are all great alternatives to Canada thistle. These species are tall, herbaceous, perennial flowers that are extremely similar to Canada thistle. All of these would be great choices for replanting areas where Canada thistle has been removed.