Canada Thistle
Cirsium arvense (L.) Scop.
Family: Asteraceae, Aster
Genus: Cirsium
Other names: Canadian thistle, creeping thistle
Nomenclature: arvense = of cultivated fields
Nativity / Invasiveness: noxious weed in Montana
Edible plant
Medicinal plant

General: plant 30-150 cm tall. Growth habit: erect perennial from deep-seated creeping roots, often forming colonies. Stems: leafy, branched, not winged.

Leaves: alternate, lance-shaped, 5-15 cm long, spiny-toothed and deeply lobed to wavy along edges, usually stalkless, usually almost hairless, or the leaves more or less white-woolly beneath.

Flowerheads: pink-purple or occasionally white, 12-25 mm wide, with disk florets only, usually either male or female on 1 plant, more or less numerous on spineless stalks in open, spreading clusters. Pappus of the female heads exceed the corollas, that of the male heads are shorter than the corollas. Involucre 1-2 cm high, its bracts sometimes with weak spine tips about 1 mm long. June-August.

Fruits: flattened, ribbed achenes, about 4 mm long, with pappus of brownish to white, feathery bristles.


A noxious weed of fields and waste places in parts of w. c. and s. parts of MT. Native of Eurasia, now widely introduced in n. U. S. and s. Canada.
Edible Uses

The roots of first year plants can be eaten raw or cooked. They are nutritious but rather bland, and are best used in a mixture with other vegetables. The root is likely to be rich in inulin, a starch that cannot be digested by humans. This starch thus passes straight through the digestive system and, in some people, ferments to produce intestinal gases. The stems can be peeled and cooked like asparagus or rhubarb. Leaves - raw or cooked - are edible too. They have a fairly bland flavor, and the prickles need to be removed before the leaves can be eaten - not only is this rather tedious but very little edible leaf remains.

Medicinal Uses

The root has been chewed as a remedy for toothache. A decoction of the roots has been used to treat worms in children.

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