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FNA | Family List | FNA Vol. 19, 20 and 21 | Asteraceae | Cirsium

51e. Cirsium eatonii (A. Gray) B. L. Robinson var. hesperium (Eastwood) D. J. Keil, Sida. 21: 212. 2004.

Tall mountain thistle

Cnicus hesperius Eastwood, Bull. Calif. Acad. Sci., ser. 3, 1: 122. 1898; Cirsium hesperium (Eastwood) Petrak

Stems strictly erect, 50–150 cm. Leaf faces glabrous or nearly so or abaxially finely arachnoid-tomentose and/or villous to tomentose with septate trichomes on one or both faces. Heads usually sessile in stiffly erect, tight spiciform arrays, sometimes also sessile in distal leaf axils. Involucres 2–2.5 cm, tomentose with septate trichomes; outer phyllaries with a few stiff lateral spines; spines of phyllaries slender. Corollas pink or pale to deep purple, 14–21 mm, tubes 4.5–10 mm, throats 3.5–5 mm, lobes 3.5–7 mm. Pappi 8–17 mm.

Flowering summer (Jul–Sep). Rocky slopes, sub-alpine meadows, forest openings; 2700–3400 m; Colo.

Variety hesperium is distributed in the San Juan Mountains and Spanish Peaks area of southern Colorado. It differs from var. eriocephalum in its stiffly erect arrays. Plants from the Spanish Peaks area approach var. eriocephalum.


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