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Plumeless thistle
Carduus acanthoides L.

Plumeless thistle tends to be shorter than other invasive thistles and generally reaches 1 to 4 feet tall. Plumeless thistle is a winter annual or biennial and is generally found only in eastern North Dakota.

Plumeless thistle can become very weedy and form dense colonies, especially along waterways, ditches, and roadsides in summers following wet falls. Plumeless thistle is seldom found in cultivated fields, even when infestations are nearby in roadsides or pastures.

The leaves are more deeply lobed and narrower than musk thistle and very pubescent underneath.

Each lobe has one to three pointed marginal spines which are short but very sharp.

Flowering plumeless thistle showing spiny winged stems that completely extend up and down the stem unlike musk thistle.

Plumeless thistle stems are winged and very branched giving the plant a candelabrum appearance. The wings are very spiny and are continuous along the stem and not interrupted like musk thistle.

The heads are small (0.5 to 1 inch in diameter) but very numerous and pink to purple in color or very rarely white. The bracts beneath the flowers are very narrow and resemble spines. The heads can be singular or in clusters of 2 to 5.

The achenes are small, gray to light brown with a distinct, light apical collar and slightly curved. Plumeless thistle flowers from May to August.
Rosettes of plumeless thistle resemble those of musk thistle, except they are more deeply lobed and much more pubescent. Plumeless thistle rosettes have wavy leaves with yellow spines along the white-colored leaf margins.

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