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Astragalus amnis-amissi
Astragalus amnis-amissi Barneby ex C.L. Hitchc.
Custer Milkvetch
Fabaceae (Pea family)
Synonym(s):
USDA Symbol: ASAM4
USDA Native Status: L48 (N)
"Slender, caulescent, with a taproot and shortly forking aerial caudex, strigulose with fine, straight, appressed or subappressed hairs up to 0.3-0.4 mm. long, the herbage green, the leaflets thinly pubescent to nearly glabrous above (exceptionally, in some upper leaves, more densely pubescent above than beneath); stems few (± 2-7), weakly ascending, 1-2.5 dm. long, simple or feebly spurred at base, floriferous from ± 3-6 nodes upward from near or commonly from well below the middle." (bibref: 1814).
"The Lost River milk-vetch, A. amnis-amissi, is closely related to A. amblytropis, but the essentially simple stems arising from a superficial root-crown and caudex, the slightly larger flowers, and especially the smaller, semibilocular, relatively few-ovulate pod provide amply satisfactory specific differences. The leaves are of thinner texture than in A. amblytropis and much more thinly strigulose; but in one plant of the type-series, the leaflets of some upper leaves are more densely pubescent above than beneath and cinereous when young, so a greater variation in this direction must be anticipated as the species becomes better known. Furthermore, a caulescent astragalus similar to A. amnis-amissi, except for the apparently buried root- crown and the silvery-glaucescent foliage, has been collected in young flower on a "moist hillside by aspens" at the Forks of the Wood River, Blaine County, Idaho." (bibref: 1814).
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Plant Characteristics
Duration: PerennialHabit: Herb
Leaf Arrangement: Alternate
Fruit Type: Legume
Size Notes: "Stems few (2-7), weakly ascending, 1-2.5 dm. long." (bibref: 1814).
Leaf: "Stipules 1.5-5 mm. long, the small, triangular-ovate lower ones papery- membranous, pallid or brownish, the larger median and upper ones ovate or broadly lanceolate, herbaceous, mostly reflexed, all strongly, often fully amplexicaul, but free or only very obscurely connate; leaves (3) 4-9.5 cm. long, slender- petioled, with (7) 9-13 broadly ovate-oblong or oblong-elliptic, retuse or emarginate (in some lower leaves small and obcordate) flat, thin-textured, faintly penninerved leaflets (3) 4-15 (18) mm. long." (bibref: 1814).
Flower: "Peduncles slender, at anthesis incurved-ascending, divaricate or recurved in fruit, (2) 3-6 (8) cm. long, shorter than the leaf; racemes loosely but shortly 5-12-flowered, the flowers at first ascending, spreading or loosely declined in age, the axis somewhat elongating, 1-3 cm. long in fruit; bracts submembranous, ovate or lanceolate, 1-2 mm. long; pedicels at anthesis slender, ascending, 1-1.7 mm. long, in fruit either ascending or arcuately recurved, scarcely thickened, 1.7-2.2 mm. long; bracteoles 0-2, minute when present; calyx 4-5.9 mm. long, strigulose with black or mixed black and white hairs, the subsymmetric disc 0.4-1 mm. deep, the submembranous, green or purplish, campanulate tube 2-3 mm. long, 1.9-2.1 mm. in diameter, the subulate or lance-subulate teeth 1.8-2.9 mm. long; petals whitish distally suffused with purplish-blue, the banner sometimes purple-striate, the keel-tip prominently maculate; banner recurved through about 40 degrees, broadly ovate-cuneate, rather deeply notched, 8.8-10.4 mm. long, 5.6-8 mm. wide; wings (0.6 mm. shorter to 0.5 mm. longer than the banner) 8.6-10.5 mm. long, the claws 2.4-3.1 mm., the oblong- oblanceolate, obtuse or emarginate, straight blades 7-8.4 mm. long, 2.2-3.1 mm. wide; keel (0.5-1.1 mm. shorter than the banner) 7.8-9.8 mm. long, the claws 3-3.8 mm., the broadly half-oblong-obovate blades 5.3-6.6 mm. long, 2.5-3.1 mm. wide, abruptly incurved through 90 degrees to the bluntly deltoid apex, truncate in profile; anthers (0.4) 0.5-0.6 mm. long." (bibref: 1814).
Fruit: "Pod ascending or loosely spreading (humistrate), sessile, subsymmetrically ellipsoid or ovoid-ellipsoid, moderately inflated but not strongly bladdery, about 1.5-1.7 cm. long, 7-8 mm. in diameter, a little obcompressed, shallowly and openly sulcate ventrally, the thin, green or purplish, strigulose valves becoming papery, stramineous, finely cross-reticulate, inflexed as a partial septum about 1.6 mm. wide, the funicular flange narrow, about 0.5 mm. wide; ovules 16-20; dehiscence and seeds unknown." (bibref: 1814).
Bloom Information
Bloom Color: White , Blue , PurpleBloom Time: Jun , Jul , Aug
Bloom Notes: "Petals whitish distally suffused with purplish-blue, the banner sometimes purple-striate, the keel-tip prominently maculate." (bibref: 1814).
Distribution
USA: IDNative Distribution: "Known only from the canyon of Pass Creek, in the Lost River Mountains, southeastern Custer County, Idaho." (bibref: 1814).
Native Habitat: "Rock crevices and talus under limestone cliffs, 6300-6600 feet." (bibref: 1814).
Bibliography
Bibref 1814 - Atlas of North American Astragalus Volume 2 (1964) Barneby, Rupert C.Search More Titles in Bibliography
Additional resources
USDA: Find Astragalus amnis-amissi in USDA PlantsFNA: Find Astragalus amnis-amissi in the Flora of North America (if available)
Google: Search Google for Astragalus amnis-amissi
Metadata
Record Modified: 2020-12-07Research By: Joseph A. Marcus