Astragalus serenoi
Minnesota Bot. Stud. 1: 130. 1894.
Plants robust, 15–45(–53) cm, strigulose. Stems erect or ascending, sparsely strigulose. Leaves 2–15 cm; stipules 1.5–5 mm, papery-scarious at proximal nodes, subherbaceous at distal nodes; leaflet blades linear, linear-oblanceolate, or filiform, 5–30 mm, apex acute, subacute, or, often, mucronate, surfaces silvery-canescent, more densely so adaxially; terminal leaflet sometimes decurrent distally, not jointed to rachis. Peduncles erect, 3–25 cm. Racemes (3–)5–25-flowered; axis 2–20 cm in fruit; bracts 1.5–4 mm; bracteoles 2. Pedicels 0.7–4 mm. Flowers 14.5–26 mm; calyx 7.9–13.7 mm, strigulose, tube 6.5–10 mm, lobes lanceolate-subulate, 1.5–4.3 mm; corolla keel 12.8–18.5 mm. Legumes firmly attached to receptacle, falling while still attached to pedicel, stramineous, straight or slightly incurved, obliquely ovoid or plumply oblong, 15–31 × 5–12 mm, fleshy becoming woody, glabrous; septum (0–)1–2.5(–4) mm wide.
Distribution
w United States.
Discussion
Varieties 3 (3 in the flora).
The vernacular name for Astragalus serenoi, naked milkvetch, refers to the persistent fruits borne naked because of the fragile calyx that is soon deciduous by a circumscissile fracture (R. C. Barneby 1964). The plant is coarse, scarcely leafy, with nearly zigzag stems.
Selected References
None.
Lower Taxa
Key
| 1 | Corollas ochroleucous and margined or tinged lavender, petals not especially graduated, banners 14.5–16 mm; legumes unilocular or subunilocular, septae 0–1 mm wide; Esmeralda and Nye counties, Nevada. | Astragalus serenoi var. sordescens |
| 1 | Corollas purple, petals strongly graduated, banners 17–24(–26) mm; legumes unilocular or semibilocular, septae 2–4 mm wide; California, Nevada. | > 2 |
| 2 | Legumes unilocular, septae 0 mm; nc Humboldt County southward to Churchill and adjacent Lander and nw Nye counties, Nevada. | Astragalus serenoi var. serenoi |
| 2 | Legumes semibilocular, septae 2–4 mm wide; Lyon and Mineral counties, southward through Esmeralda County, Nevada, to Inyo and Mono counties, California. | Astragalus serenoi var. shockleyi |