UW Burke Herbarium species comparison

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Cirsium altissimum

Cirsium arvense

Canadian thistle, creepiing thistle
Habit Dioecious, mostly glabrous perennial from deep rhizomes, 3-15 dm. tall.
Leaves

Leaves lanceolate or oblong, up to 2 dm. long, reduced upward, pinnatifid or occasionally merely lobed or toothed, weakly spiny.
Flowers

Heads several;

involucres 1-2 cm. high, the outer bracts tipped with weak, short spines;

pappus of the pistillate heads longer than the corollas, that of the staminate heads shorter than the corollas;

flowers pink-purple or occasionally white.
Fruits

Achenes glabrous, about 4 mm. long.

Cirsium altissimum

Cirsium arvense
Flowering time May-October
Habitat Roadsides, fields, meadows, pastures, prairies, grasslands, wastelots, and other disturbed areas at low to middle elevations.
Distribution
[WildflowerSearch map]
[BONAP county map]
Widely distributed on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast.
[WildflowerSearch map]
[BONAP county map]
Origin Introduced from Eurasia
Conservation status Not of concern
Sibling taxa
C. arvense, C. brevifolium, C. brevistylum, C. edule, C. flodmanii, C. hookerianum, C. inamoenum, C. remotifolium, C. scariosum, C. undulatum, C. vulgare
C. brevifolium, C. brevistylum, C. edule, C. flodmanii, C. hookerianum, C. inamoenum, C. remotifolium, C. scariosum, C. undulatum, C. vulgare
Web links 
Unless otherwise noted, all data comes from the University of Washington's Burke Herbarium.



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