Plants robust, coarse, 25–90(–100) cm, villous; from stolon­iferous, superficial or slightly subterranean caudex. Stems ascending to erect, vil­lous. Leaves (6–)9–17 cm; stipules reflexed, connate-sheathing at proximal nodes, distinct at distal nodes, 10–22 mm, foliose becoming papery-membranous; leaf­lets (7 or)9–15, blades broadly lanceolate- or ovate-oblong or elliptic, 15–60 mm, thin, pinnately veined, apex obtuse, surfaces sparsely villous abaxially, glabrous adaxially. Peduncles erect, (3.5–)5–14(–19) cm, equaling or shorter than subtending leaf, sometimes exceeding proximal ones, together with racemes usually not longer than distalmost leaves. Racemes 10–25(–30)-flowered; axis 2–5 cm in fruit; bracts 4–9 mm; bracteoles 0 or 2. Pedicels 3–9 mm. Flowers 8–13(–14.2) mm; calyx campanulate, (4.5–)4.9–5.8 mm, glabrous, tube (4.3–)4.9–5.8 mm, lobes deltate (often reduced to shallow crenulations), 0.2–0.7 mm, ciliate; corolla white or cream, keel 10.3–12.7 mm. Legumes stramineous, straight, obliquely ellipsoid, bladdery-inflated, 20–28 × 6.5–9.5 mm, papery, translucent, glabrous; stipe 4.5–7 mm. Seeds 6–9. 2n = 16.

Phenology: Flowering late Jun–Aug.
Habitat: Gravelly or sandy soils in woods or thickets, glades, grasslands, stream banks, roadsides.
Elevation: 0–2200 m.

Distribution

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Alta., B.C., Man., N.W.T., Ont., Que., Sask., Yukon, Alaska, Colo., Idaho, Mont., S.Dak., Wyo.

Discussion

R. C. Barneby (1964) noted that the geographically isolated Astragalus gaspensis is connected to A. americanus along its main Cordilleran range through populations in central Canada and that the fruits and length of calyx lobes are not distinctive. D. Isely (1998) pointed out that A. americanus is sufficiently similar to the Eurasian A. frigidus (Linnaeus) A. Gray that the two might be united.

Selected References

None.

Lower Taxa

None.