Duration: Perennial
Nativity: Native
Lifeform: Forb/Herb
General: Tufted perennial herb, to about 20 cm tall, from a branching caudex; stems lacking or short and prostrate, up to 15 cm long, with internodes less than 2 cm long and often hidden by stipules; herbage covered with greenish-gray to silvery-silky hairs.
Leaves: Alternate and pinnately compound, 4-16 cm long, with 11-27 leaflets per leaf; leaflets obovate to oblanceolate, 4-17 mm long, with entire margins, the upper surface sometimes less hairy and brighter green than the lower surface; stipules 2-15 mm long, wrapping partly around the stem.
Flowers: Purplish, in terminal racemes on leafless flower stalks to 4-40 cm long, with the flowers ascending to spreading or slightly declined at maturity; flowers about 2 cm long, with pea-flower morphology (papilionaceous), with a wide upper petal called the banner, two smaller lateral petals called the wings, and a boat-shaped lower petal called the keel which contains the style and stamens. Petals pink-purple to dull lilac, or occasionally off-white and tipped with purple; sepals 5, hairy, united into a tube 4-10 mm long, topped with 5 narrow teeth, 1-4 mm long.
Fruits: Pods ascending (pointing upward), oblong-lanceolate to ovate, laterally compressed and curved into a crescent-shape, 1-4 cm long and 5-16 mm wide, unilocular, strigose, and thinly leathery to slightly woody at maturity; lacking a stipe (short stalk at the
Ecology: Found on open dry ground to rocky slopes, from 3,500-8,000 ft (1067-2438 m); flowers April-June.
Distribution: s NV to sw CO, south to s AZ, sw NM, and neighboring MEX.
Notes: This is a mostly acaulescent (lacking a stem) Astragalus, with the leaves appearing mostly basal, and leafless flower stalks usually elevating the flowers above the tops of the leaves. However, the species sometimes takes on a prostrate, spreading growth form with leafy stems up to 15 cm long that grow along the ground; when that is the case, the stem internodes are still quite short, no more than 2 cm long. This is a morphologically variable and taxonomically muddy species. The two most common and well-defined varieties are var. brachylobus and var. tephrodes. The former is the widest-ranging, from western New Mexico through Arizona along the Mogollon Rim, to southwest California, and is distinguished by having longer calyx tubes, 7-10 mm long; longer seed pods, 2-3 cm long; and flat leaflets. Var. tephrodes is found in western New Mexico and extreme eastern Arizona, and is distinguished by having shorter calyx tubes, 4-7 mm long; smaller seed pods, 1-2 cm long; and folded leaflets. Distinguish from A. missouriensis based on the shape of the seed pods (mostly straight, and round in cross-section (terete) in A. missouriensis; laterally complessed and somewhat crescent-shaped in A. tephrodes).
Ethnobotany: Unknown
Etymology: Astragalus comes from the Greek astragalos, ankle bone, an early name applied to some plants in this family because of the shape of the seeds; tephrodes is from the Greek tephros for ash colored, probably referring to the grayish pubescence covering the leaves.
Synonyms: None
Editor: SBuckley 2010, AHazelton 2017
