Pests Addressed

A perennial with extensive underground creeping roots – which makes this weed a challenge to control. Canada thistle is a native of Eurasia but was introduced to North America in the late 18th century.

DID YOU KNOW?

1. Biological control - Canada thistle gall-fly or stem-mining weevil feed on foliage

2. Mechanical control – mowing just prior to flowering inhibits spread and seed production. Chemical control is effective for herbicides registered for Canada thistle. Always read and follow label directions.

Identification

Roots:

Deep horizontal and vertical creeping roots which are the primary method of spread.

Leaves:

Rosette leaves are smooth, irregularly lobed, and the leaf margins have spiny teeth.

Stem:

Grows erect, hairless, and hollow in cross-section. Plants can grow up to 1.2 m in height.

Flowers:

Pink, purple, or white flowers arranged in clusters and smaller than others in the thistle family. Plants are either male or female, but only female flowers can produce seed.

Seeds:

Single tan-colored seeds with a slight curve; each seed has a feathery pappus to disperse via wind.