Burke: Centaurea solstitialis vs. Centaurea calcitrapa

	Centaurea solstitialis	Centaurea calcitrapa
	yellow star-thistle	purple starthistle, red starthistle
Habit	Annual or biennial, 2-8 dm. tall, thinly white-woolly throughout, the stem winged.
Leaves	Basal leaves lyrate and pinnatifid, up to 20 cm. long and 5 cm. wide; cauline leaves smaller, becoming linear and entire upward.
Flowers	Heads several, broader toward the base; involucre 10-15 mm. high, its middle and outer bracts spine-tipped, the larger spines 11-22 mm. long; flowers yellow; pappus of the outer flowers wanting, that of the others 3-5 mm. long; receptacle densely bristly.

	Centaurea solstitialis	Centaurea calcitrapa
Flowering time	July-September	July-September
Habitat	Roadsides, fields, ditches, meadows, grassy slopes, wastelots, and other disturbed, open areas at low to middle elevations.	Roadsides, fields, ditches, wastelots, and other disturbed, open areas.
Distribution	Occurring chiefly east of the Cascades crest and in the Columbia River Gorge in Washington; Washington to California, east across most of North America to the Atlantic Coast. [WildflowerSearch map] [BONAP county map]	Occurring east of the Cascades crest in Washington; Washington to California, east to New Mexico, also in eastern North America. [WildflowerSearch map] [BONAP county map]
Origin	Introduced from Europe	Introduced
Conservation status	Not of concern	Not of concern
Sibling taxa	C. benedicta, C. calcitrapa, C. cyanus, C. diffusa, C. ×gerstlaueri, C. iberica, C. jacea, C. macrocephala, C. melitensis, C. montana, C. nigra, C. nigrescens, C. stoebe, C. trichocephala, C. ×varnensis	C. benedicta, C. cyanus, C. diffusa, C. ×gerstlaueri, C. iberica, C. jacea, C. macrocephala, C. melitensis, C. montana, C. nigra, C. nigrescens, C. solstitialis, C. stoebe, C. trichocephala, C. ×varnensis
Web links	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria, Turner Photog. WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Centaurea solstitialis

Centaurea calcitrapa

yellow star-thistle

purple starthistle, red starthistle

Habit

Annual or biennial, 2-8 dm. tall, thinly white-woolly throughout, the stem winged.

Leaves

Basal leaves lyrate and pinnatifid, up to 20 cm. long and 5 cm. wide;

cauline leaves smaller, becoming linear and entire upward.

Flowers

Heads several, broader toward the base;

involucre 10-15 mm. high, its middle and outer bracts spine-tipped, the larger spines 11-22 mm. long;

flowers yellow;

pappus of the outer flowers wanting, that of the others 3-5 mm. long;

receptacle densely bristly.

Centaurea solstitialis

Centaurea calcitrapa

Flowering time

July-September

Habitat

Roadsides, fields, ditches, meadows, grassy slopes, wastelots, and other disturbed, open areas at low to middle elevations.

Roadsides, fields, ditches, wastelots, and other disturbed, open areas.

Distribution

Occurring chiefly east of the Cascades crest and in the Columbia River Gorge in Washington; Washington to California, east across most of North America to the Atlantic Coast.

[WildflowerSearch map]

[BONAP county map]