Centaurea melitensis |
Centaurea macrocephala |
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Maltese starthistle, tocalote |
globe knapweed |
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Habit | Annual, 1.5-7 dm. tall, lightly covered with crisp hairs, the stem with narrow wings from the leaf bases. | Perennial herbs, the several stems 50-170 cm. tall, erect, sparingly branched, thinly woolly. |
Leaves | Basal and lower cauline leaves oblanceolate, toothed to lyrate-pinnatifid, 3-15 cm. long and 5-35 mm. wide, usually deciduous; middle and upper cauline leaves smaller, becoming linear-oblong and entire upward. |
Leaves alternate, the basal and lower cauline petiolate, becoming sessile upward; leaf blades dotted with glands, oblanceolate to narrowly ovate, 10-30 cm. long, entire or shallowly dentate. |
Flowers | Heads few to numerous; involucre 8-15 mm. high, broader toward the base, its middle and outer bracts spine-tipped, the central spine 5-9 mm. long; the inner bracts purple tinged; flowers yellow, all alike; pappus 1.5-3 mm. long; receptacle strongly bristly. |
Heads borne singly, sessile, closely subtended by clusters of reduced leaves; involucres ovoid to hemispheric, 25-35 mm. long, the involucral bracts glabrous, ovate to broadly lanceolate, pale green, with abruptly spreading appendages, brown, scarious, 1-2 cm. wide; flowers many, yellow, the outer sterile corollas slightly longer than the central, fertile corollas; pappus of flattened bristles 5-8 mm. long. |
Fruits | Achenes 7-8 mm. long. |
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Centaurea melitensis |
Centaurea macrocephala |
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Flowering time | June-September | June-September |
Habitat | Roadsides, meadows, balds, fields, ditches, wastelots, and other disturbed, open areas at low to middle elevations. | Roadsides and meadows. |
Distribution | Occurring chiefly west of the Cascades in Washington; British Columbia to California and Mexico, east to Texas and eastern North America.
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Occurring east of the Cascades crest in Washington; central Washington to Montana, also in Colorado, and Great Lakes region to northeastern North America.
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Origin | Introduced from the Mediterranean region | Introduced from Eurasia |
Conservation status | Not of concern | Not of concern |
Sibling taxa | ||
Web links |
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