Monographs Details: Astragalus collinus Douglas ex Hook. var. collinus
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.
Family:Fabaceae
Synonyms:Phaca collina Hook., Tragacantha collina (Hook.) Kuntze, Homalobus collinus (Hook.) Rydb.
Description:Variety Description - Stipe of the pod (5) 6-15 mm. long; otherwise as given in the key. [Key: "Pod slenderly linear-oblong in profile 0.7-2.5 cm. long, 2.5-3.4 (4) mm. in diameter, straight or rarely a little incurved, the valves villosulous or loosely strigulose with hairs up to 0.25-0.5 mm. long; ovules (10) 12-18"]

Distribution and Ecology - Bunchgrass prairies, grassy hillsides, and sagebrush valleys, in light sandy or stony soils overlying basalt, 900-3100 feet, forming colonies and locally abundant in central and southeastern transmontane Washington, extending southeast along the Snake River and its affluents from the south into westcentral Idaho and the north foothills of the Wallowa and Blue Mountains in Oregon, westward into Umatilla County; also apparently isolated on the upper Okanogan and lower Thompson Rivers in southern British Columbia.—Map No. 28.—May to July.

Discussion:Within its area of dispersal the hill milk-vetch, A. collinus, is easily recognized by its greatly modified flower, remarkable for the tumid, basally pouched calyx of nearly the same color as the creamy petals, and for the relatively short, sigmoidally arched banner. The body of the pod is ordinarily straight, but is sometimes a trifle arched upward or downward. A noteworthy collection from Idaho County, Idaho, (Constance 1847, WS, WTU) combines a rather long, gently incurved pod with a developed banner, its limb recurved through about 50° rather than abruptly folded back a little below the apex. This may possibly represent a distinct race cut off from the main area of the species by the deeply dissected topography of the Salmon River canyon, but for the present too little evidence is available on which to base an opinion.
Distribution:Washington United States of America North America| Idaho United States of America North America| Oregon United States of America North America| British Columbia Canada North America|