Astragalus humistratus var. tenerrimus
Proc. Calif. Acad. Sci., ser. 2, 5: 649. 1895.
Plants forming loose mats, to 8+ dm wide, strigulose, hairs ± straight, sometimes shorter ones crispate or sinuous, herbage greenish cinereous or silvery. Stems 10–30 cm, sometimes 1–3 cm underground. Stipules 1.5–4.5(–5.5) mm. Leaves 1–3(–4) cm; leaflets (9 or)11–15, blades 2–6.5 mm, surfaces pubescent or glabrescent adaxially. Peduncles 1–3(–4) cm. Racemes 3–6(–8)-flowered; axis 0.5–2 cm in fruit. Flowers: calyx 3.2–4.7 mm, tube 2.1–2.7 mm, lobes subulate, 1–1.2 mm; corolla whitish, veined or suffused with lilac-purple; banner 5.9–7.2 × 5.2–6.6 mm. Legumes lunately semi-ovoid-ellipsoid, 6–9 × 3–4.5 mm, loosely strigulose. Seeds 9–14.
Phenology: Flowering Jul–Sep.
Habitat: Meadows, ponderosa pine, white fir, and spruce forests, margins of aspen stands.
Elevation: 2400–2800 m.
Discussion
Variety tenerrimus, a diminutive Kaibab Plateau endemic, may deserve specific status as proposed by P. A. Rydberg (1929) in the segregate genus Batidophaca Rydberg. R. C. Barneby (1964) considered it closely allied to var. humivagans.
Selected References
None.