Astragalus robbinsii

Plants clump-forming, slender to robust, 7–45(–60) cm, strigu­lose to pilose-villosulous; from superficial or somewhat subter­ranean caudex. Stems usually ascending, rarely decumbent, 0–2 cm underground, strigu­lose to pilose-villosulous. Leaves 2.5–12 cm; stipules 1.5–6 mm, papery at proximal nodes, herbaceous or submembranous at distal nodes; leaflets (5 or)7–17, blades lanceolate to oblong, (3–)5–30(–32) mm, apex obtuse or emarginate, surfaces usually strigulose, sometimes villous-pilosulous, cinereous, glabrate, or glabrous abaxially, glabrous, glabrescent, or sparsely strigose adaxially. Peduncles incurved-ascending or erect, 3.5–21(–23) cm, usually surpassing subtending leaf, together with racemes usually shorter than stems. Racemes (3–)5–25(–33)-flowered; axis 1–18(–20) cm in fruit, elongating little after flowering, arising distal to middle of stem; bracts 1–3.5 mm; bracteoles usually 0. Pedicels 0.5–3 mm. Flowers (6–)7.2–11.5 mm; calyx 4–6.8 mm, strigulose, tube 3.2–4.5 mm, lobes subulate, 0.7–2.3 mm; corolla usually purple, pink-purple, pink, lilac, lavender, or whitish, sometimes whitish with maculate keel; wing apex obtuse; keel 5.4–7.9 mm, shorter than wings. Legumes pendulous, green or purplish, straight or slightly decurved, ellipsoid, obtusely 3-sided, faces slightly con­vex, flattened or depressed but not sulcate abaxially, 13–25 × 3.5–5.5 mm, subunilocular or semibilocular, papery-membranous, sparsely strigulose, hairs black or black and white; valves inflexed as hyaline septum 0.2–2 mm wide; stipe (0.5–)1.5–6.5 mm. Seeds 6–11.

Distribution

North America.

Discussion

Varieties 8 (8 in the flora).

Astragalus robbinsii consists of a series of infra­specific taxa with two centers of dispersal in North America: Colorado to Alaska, and New England into eastern Canada. The distribution of three closely allied subordinate taxa within Vermont and New Hampshire is unmatched in the genus in North America. D. Isely (1998) questioned the taxonomic significance of the traditional varieties as recognized herein. The species is often confused in herbaria with A. alpinus, which has a keel longer than or as long as and wider than the wings (in A. robbinsii the keel is shorter than and little or no wider than the wings).

Selected References

None.

Lower Taxa

Astragalus robbinsii var. alpiniformis, Astragalus robbinsii var. fernaldii, Astragalus robbinsii var. harringtonii, Astragalus robbinsii var. jesupii, Astragalus robbinsii var. minor, Astragalus robbinsii var. morganiae, Astragalus robbinsii var. occidentalis, Astragalus robbinsii var. robbinsii

Key

1	Leaflet blade surfaces abaxially densely gray or white villous-pilosulous, hairs 0.6–0.8 mm; legume stipes 1.2–3 mm, septae 1.2–2 mm wide; s coastal Alaska.	Astragalus robbinsii var. harringtonii
1	Leaflet blade surfaces abaxially sparsely strigu­lose, cinereous, glabrous, or glabrate, hairs 0.2–0.6(–0.7) mm; legume stipes (0.5–)1.5–5(–6.5) mm, septae 0.2–1(–1.5) mm wide; not in s coastal Alaska.	> 2
2	Legume stipes (1–)1.5–5(–6.5) mm; Alaska, New England, Nova Scotia, n Rocky Mountains.	> 3
3	Stems 7–10 cm; racemes 5–11-flowered, axes 1–1.5 cm in fruit (barely elongated); legume stipes 5 mm; seeds 5 or 6; Mt. Roberts, near Juneau, Alaska.	Astragalus robbinsii var. morganiae
3	Stems 10–40(–60) cm; racemes (5–)7–21-flowered, axes (1–)3–18(–20) cm in fruit; legume stipes (1–)1.5–5(–6.5) mm; seeds (6 or)7–11.	> 4
4	Legumes 10–15 mm, sparsely strigu­lose, beaks to 1 mm; corollas whitish; Vermont historically.	Astragalus robbinsii var. robbinsii
4	Legumes (10–)13–25 mm, sparsely or densely pubescent, beaks 0.8–3 mm; corollas pale purple, pink-purple, pink, or whitish and keel tip purple; widespread, including Vermont.	> 5
5	Legumes sparsely strigose-pilosulous, beaks 0.8–1.5 mm; leaf­let blade surfaces uniformly strigu­lose abaxially, or glabrate through­out; Alaska, Canada, w United States, Maine and Vermont.	Astragalus robbinsii var. minor
5	Legumes sparsely strigulose, beaks 1.5–3 mm; leaflet blade surfaces cinereous abaxially, pubescent adax­ially (margins sparsely pubescent); local along Connecticut River in Vermont and New Hampshire.	Astragalus robbinsii var. jesupii
2	Legume stipes 0.5–3(–6.5) mm; coastal Labrador, adjoining Newfoundland, e Quebec to Alberta, northward to Northwest Territories, southward to New Mexico, including Maine and Vermont.	> 6
6	Seeds 3–6; legumes 8–13 mm; Wallowa Mountains, ne Oregon.	Astragalus robbinsii var. alpiniformis
6	Seeds (6 or)7–10; legumes (8–)10–25 mm; not Oregon.	> 7
7	Raceme axis 1.2–6(–8) cm in fruit; leaflet blade surfaces sparsely pubescent along margins adaxially or strigulose throughout; s Labrador, adjoining Newfoundland, Quebec.	Astragalus robbinsii var. fernaldii
7	Raceme axis (2–)3–18(–20) cm in fruit; leaflet blade surfaces glabrous or glabrate adaxially; not s Labrador, adjoining Newfoundland, and Quebec.	> 8
8	Legumes (10–)13–25 mm, stipes (1–)1.5–5(–6.5) mm; racemes (5–)7–25(–33)-flowered, axes (2–)3–18(–20) cm in fruit; proximal stipules distinct or obscurely connate; not ne Nevada.	Astragalus robbinsii var. minor
8	Legumes (8–)10–15(–18) mm, stipes 0.5–1.4 mm; racemes remotely (3–)6–12-flowered, axes (2–)6–15 mm in fruit; proximal stipules connate 1/2 their length; East Humboldt and Ruby mountains, ne Nevada.	Astragalus robbinsii var. occidentalis