The
photo at right illustrates a lateral view of a flower head of Arnica amplexicaulis
var. piperi as seen from McCord Creek Falls (lower falls) in the Columbia River Gorge...........July
14, 2006. Note the narrow involucral bracts covered with sparse hairs.
Streambank arnica is also known as clasping arnica.
It is a fairly attractive perennial with several to many upright stems arising from 30-80 cm high from freely rooting rhizomes. The herbage of the stems is more or less hairy and glandular. The stems are noticeably leafy with 5-12 pairs of opposite leaves which are relatively the same size along the whole stem. Individual leaves are narrowly lance-elliptic to lance-ovate in shape with either short petioles on the lower leaves to lacking petioles on the upper leaves. The leaves range from 5-12 cm long and 1.2-6 cm wide and have toothed margins (See photos below.). There are several bell-shaped heads with the involucral bracts (seen at right) narrowly lanceolate with acute to acuminate tips covered with sparse hairs or glandular hairs. The 8-14 yellow rays are 1-2 cm long and surround a yellow central disk.
Variety amplexicaulis: Has thinner leaves (up to 4 cm wide). Found in the range of the species which includes the Columbia River Gorge.
Variety piperi: Has thicker leaves (up to 6-8 cm wide). Found only in the Columbia River Gorge.
Streambank arnica is found in wet meadows, along streambanks, and in the spray zone around waterfalls.
Variety amplexicaulis may be found from Alaska south to northern California and east to western Montana. In the Columbia River Gorge it may be found between the elevations of 100'-4000' from Cape Horn east to the White Salmon River.
Variety piperi is found only in the Columbia River Gorge where it is found between the elevations of 100'-1500' from east of the Sandy River to Dog Creek Falls.
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