Astragalus layneae

Plants short-lived, somewhat coarse, 15–35 cm, pilosulous to gray-strigulose; from branching caudex, branches becoming rhizomatous. Stems erect or nearly so, 1–7(–10) cm underground, becoming abruptly stouter on emergence, clump-forming at irregular intervals along subterranean rhizome, gray-strigulose to pilosulous. Leaves (4–)6–16 cm; stipules 3–10(–12) mm, membranous throughout or herbaceous at distal nodes; leaflet blades ovate, obovate, rhombic-ovate, obovate-cuneate, broadly elliptic, or suborbiculate, 5–18(–23) mm, apex obtuse or shallowly retuse, surfaces strigulose-pilosulous. Peduncles erect, 4.5–10(–14) cm. Racemes (12–)15–45-flowered; axis (3–)5–20(–30) cm in fruit; bracts 2.5–6 mm; bracteoles 2. Pedicels 0.6–2.8 mm. Flowers 12.5–17.5(–18) mm; calyx 6–8.8 mm, densely hirsutulous, tube 5–7.5 mm, lobes deltate or subulate, 1–2 mm; corolla whitish and suffused, veined, or tipped with purple; keel 10.4–15.4(–16.5) mm. Legumes green, sometimes purplish, usually red-mottled, (20–)30–65 × 3.5–8 mm, fleshy becoming leathery, villosulous. 2n = 44.

Phenology: Flowering Mar–May.
Habitat: Sandy flats, washes and gentle slopes or outwash fans in foothills of desert mountains.
Elevation: 400–1600 m.

Ariz., Calif., Nev.

Discussion

Astragalus layneae, named for Katharine Layne Brandegee, western American botanist, is the only extensively rhizomatous Astragalus in the Mojave Desert; however, the rhizomes are rarely collected. This is one of the few North American Astragalus with a reported tetraploid chromosome number (x = 22), and this with meiotic abnormalities in at least one population (R. Spellenberg 1976).

Selected References

None.

Lower Taxa