Astragalus pectinatus

Plants relatively coarse, forming bushy clumps, 10–60 cm, strigulose; from branched caudex. Stems usually decumbent or ascending, sometimes erect, strigulose. Leaves 4–11 cm; stipules connate-sheathing and papery at proximal nodes, connate or distinct and herbaceous at distal nodes, 1.5–10 mm; leaflets (5–)9–15(–21), blades linear, filiform, or linear-oblanceolate, 15–70 mm, margins involute, apex acuminate, surfaces strigulose abaxially, glabrous adaxially; terminal leaflet decurrent, not jointed to rachis. Peduncles incurved-ascending, (2–)3.5–8(–10.5) cm. Racemes (7–)12–30-flowered, flowers nodding; axis 3–13(–17) cm in fruit; bracts 2–7 mm; bracteoles 0. Pedicels 2–3(–3.5) mm. Flowers (16–)21–24(–27) mm; calyx 8–12 mm, strigulose, tube 6.5–9 × 2.8–4.3 mm, lobes subulate, 1.5–3 mm; corolla white or ochroleucous, drying yellowish; keel 13.8–16 mm. Legumes declined or deflexed, stramineous or brown, straight or slightly decurved, ellipsoid or oblong-ellipsoid to clavate-ellipsoid, ± obcompressed, (10–)15–25 × (4.5–)5–8 mm, woody, glabrous; sessile. Seeds (23–)26–32. 2n = 22.

Phenology: Flowering May–Jul.
Habitat: Saline flats, bluffs, hilltops, on seleniferous substrates derived from shale.
Elevation: 400–2400 m.

Alta., Man., Sask., Colo., Kans., Mont., Nebr., N.Dak., S.Dak., Wyo.

Discussion

Astragalus pectinatus is an elevationally and geographically widely distributed selenophyte of the western Great Plains showing no sign of racial differentiation. Its leaves, with extremely long, narrow, stiffly incurved leaflets, have no exact counterpart in the genus. J. D. Karron (1989) reported it to be essentially self-incompatible, and Karron et al. (1988) found it to have higher genetic polymorphism than the geographically restricted A. linifolius and A. osterhoutii, and also the widespread A. pattersonii.

Selected References

None.

Lower Taxa