Astragalus linifolius

Plants stout, rushlike, forming bushy clumps, 35–50 cm; from shallow, subterranean or superficial caudex. Stems erect or ascending, sparsely strigulose. Leaves distally (rarely all) unifoliolate or reduced to phyllodia, 3–12 cm; stipules connate-sheathing and papery-membranous at proximal nodes, distinct and herbaceous at distal nodes, 3.5–5 mm; leaflets (0 or 1–)3–9, blades obovate or linear, 2–12 mm, apex obtuse to acute, surfaces sparsely strigulose; terminal leaflet of compound leaves decurrent, not jointed to rachis. Peduncles erect or incurved-ascending, 10–25 cm. Racemes loosely 3–10-flowered, flowers ascending; axis 1.5–9(–12) cm; bracts 2–3 mm; bracteoles 1 or 2. Pedicels 0.5–3.5 mm. Flowers 14.6–18(–22) mm; calyx 5.0–7.8 mm, strigose, tube 3.8–5.3 × 3.7–3.8 mm, lobes subulate, 1.1–2.8 mm; corolla white, keel tip pink-purple fading dark purple; keel 11.3–12.3 mm. Legumes erect, stramineous, ± straight, narrowly oblong-ellipsoid, slightly compressed laterally, (10–)12–17(–20) × 4.4–6 mm, fleshy becoming woody, glabrous or strigose; sessile. Seeds 18–20.

Phenology: Flowering May–Jun.
Habitat: Pinyon-juniper woodlands and sagebrush communities on seleniferous substrates.
Elevation: 1400–1800 m.

Colo.

Discussion

Astragalus linifolius has erect fruits and white flowers that distinguish this handsome clump-former from the morphologically similar but disjunct A. rafaelensis, with which it was synonymized by P. A. Rydberg (1929). J. D. Karron (1989) reported this species to be self-compatible and moderately autogamous, but to exhibit inbreeding depression when self-pollinated. Karron et al. (1988) reported the species to have restricted genetic polymorphism, but to still exhibit a moderate level of isozyme variation.

Astragalus linifolius is restricted to Delta and Montrose counties. It is in the Center for Plant Conservation’s National Collection of Endangered Plants.

Selected References

None.

Lower Taxa