Astragalus asclepiadoides
Plants stout, 7–62 cm, glabrous or glabrate. Stems erect, 0–7 cm underground, glabrous. Leaves crowded, loosely imbricate, 1.5–6.5 cm; stipules 2–15 mm, membranous; leaflet blade ovate, orbiculate, or cordate, 15–65 mm, apex obtuse to rounded or retuse, surfaces glabrous. Peduncles erect, 0.5–4.5 cm. Racemes 2–12-flowered; axis 0.4–2.5 cm in fruit; bracts 1–5 mm; bracteoles 2. Pedicels 1–5 mm. Flowers 17–27 mm; calyx 10–17 mm, black-strigose, tube 8.3–13 mm, lobes linear to subulate, 1.5–3.8 mm; corolla keel 14.2–18.5 mm. Legumes pale green and purple-speckled becoming stramineous, straight, 25–35 × 11–16 mm, fleshy becoming leathery or stiffly papery, glabrous; stipe 10–23 mm. 2n = 24.
Phenology: Flowering May–Jun.
Habitat: Saline desert shrub communities on fine-textured, seleniferous, Arapien, Cretaceous Mancos, and Tropic shales, Jurassic Carmel, Tertiary Duchesne River, and Triassic Moenkopi formations.
Elevation: 1200–2400 m.
Discussion
Astragalus asclepiadoides is known from western Colorado and northeastern and north-central Utah.
Astragalus asclepiadoides is unique for the genus in the flora area, with broad, leathery, unifoliolate leaves. The blade apparently represents the terminal leaflet of an ancestral imparipinnate leaf; a few Eurasian taxa show somewhat parallel modification (R. C. Barneby 1964). The leaves, though alternate, bear an uncanny resemblance to those of the milkweed Asclepias cryptoceras.
Selected References
None.