Synonyms: Other names: Chamisso arnica, American arnica Nomenclature: chamissonis = named after Chamisso Nativity / Invasiveness: Montana native plant
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Description
General: 20-100 cm tall, hairy, becoming glandular above. Growth habit: Erect perennial with stems from long, almost naked, slender rhizomes. Stems: single, leafy, with soft, wavy hairs.
Leaves: opposite, lance-shaped, in 5-10 pairs on stem, 5-25 cm long and 1-4 cm wide, clasping stem, not much reduced upwards, slightly toothed or entire, usually with 5 stronger veins. Lower leaves taper to winged stalks and upper leaves are stalkless. Variously hairy with short, woolly hairs, becoming glandular higher up.
Flowerheads: yellow, 3-5 cm across, with 10-16 rays, growing in branched clusters of 1 to several flowerheads. The involucre is mostly 8-12 mm high, with bracts that are blunt or soft-pointed, tipped with a tuft of white hairs.
Mostly June-July.
Fruits: achenes, short-hairy and glandular to almost hairless. Pappus of tawny to straw-colored, feathery bristles.
Distribution
Mostly in meadows, thickets and wet places, foothills to lower subalpine in s. and s.w. parts of MT. Also from Ontario to AK and south to NM and CA.
ssp. foliosa var. andina:
Sub taxa:
ssp. chamissonis var. interior: Pappus tawny, slightly feathery, leaves usually toothed, hairs at the base of the involucre with very prominent cross-walls.
ssp. foliosa: Pappus straw-colored or whitish, merely barbed, leaves with small teeth to more often entire. Hairs at the base of the involucre with less prominent cross-walls.
ssp. foliosa var. andina: Plants less robust and with narrower (seldom over 4 cm wide) leaves.
ssp. foliosa var. maguirei: Plants exceptionally robust, up to 1 m tall, with large (up to 6 or 8 cm wide) leaves. A striking local form in the vicinity of Lower St. Mary Lake, Glacier Co., MT.
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