Astragalus purshii
Fl. Bor.-Amer. 1: 152. 1831.
Plants tuft-forming, acaulescent, subacaulescent, or shortly caulescent, 4.5–13 cm, usually villous to villous-tomentose, sometimes appearing white or gray, hairs basifixed; from branched, superficial caudex, branches with thatch. Stems usually obscured by stipules, or internodes to 2 cm, villous to villous-tomentose. Leaves 1–12(–15) cm; stipules (2.5–)3–15 mm, membranous; leaflets (3 or)5–17(–21), blades obovate, obovate-cuneate, elliptic to oblanceolate, or rhombic-elliptic, 2–14(–20) mm, apex usually acute, subacute, acuminate, or obtuse, rarely truncate-emarginate, surfaces densely villous. Peduncles ascending or erect, decumbent in fruit, 1.5–10.5 cm. Racemes 1–11-flowered, flowers ascending; axis 0.3–2(–4) cm in fruit; bracts 2–9 mm; bracteoles 0. Pedicels 1–5 mm. Flowers 19–25(–27) mm; calyx cylindric, cylindro-campanulate, or campanulate, (5.5–)6–16(–19) mm, villous-pilose, tube (4–)4.5–12(–13.6) mm, lobes subulate, 1–6(–7) mm; corolla white, cream, purple, or pink-purple; banner recurved through 40°; keel 8–21.2(–22.5) mm. Legumes initially ascending (humistrate), brownish, not mottled or spotted, incurved, ovoid, ovoid-ellipsoid, or lanceoloid-ellipsoid, dorsiventrally compressed, 7–26(–30) × 3.5–11(–13) mm, unilocular, fleshy becoming leathery, mostly shaggy-villous, sometimes tomentose or villous-hirsute, hairs 1.6–4(–5) mm, often concealing surface; sessile or subsessile, or gynophore 0.5+ mm. Seeds 14–38(–46).
Distribution
w North America.
Discussion
Varieties 8 (8 in the flora).
The geographic distribution of Astragalus purshii, forming a relatively large triangle in western North America, from southwestern Canada to southern California, northeastward to western North Dakota, makes it the most widely distributed of all astragali with woolly fruits. The case for specific status for such entities as A. inflexus and A. utahensis may be little stronger than that for several of the taxa included within A. purshii (D. Isely 1998). L. Abrams (1944b) often gave an inclusive name of woolly-pod to all of the fuzzy-podded species, sometimes sheep-pod. For consistency they are all called milkvetch here. Isely gave a synopsis that helped to distinguish other woolly fruited species. The treatment of R. C. Barneby (1964) is followed here, and his key to varieties is largely followed.
Selected References
None.
Lower Taxa
Key
| 1 | Calyces (5.5–)6–10.1 mm; banners 9–16.5 mm; keel 8–13 mm. | > 2 |
| 2 | Racemes (3–)5–11-flowered; leaflets (7 or)9–15(or 17); sw Idaho. | Astragalus purshii var. ophiogenes |
| 2 | Racemes 1–5(–7)-flowered; leaflets (3 or)5–9(or 11); California, sw Idaho, nw Nevada, and along foothills and plains adjacent to e slope of Cascades in Oregon. | > 3 |
| 3 | Legumes incurved only in beak; seeds 24–32; San Bernardino Mountains and Sierra Nevada, California, w Nevada. | Astragalus purshii var. lectulus |
| 3 | Legumes arched throughout, at least through 0.5–1 spiral; seeds 14–20; plains of ne California to c Oregon, sw Idaho, and nw Nevada. | Astragalus purshii var. lagopinus |
| 1 | Calyces (8–)9–16(–19) mm; banners (14.6–)15.4–25(–26) mm; keel (11.5–)12.4–21.2(–22.5) mm. | > 4 |
| 4 | Corollas mostly white or cream (keel tip maculate), rarely banners and wings tipped dull, pale bluish purple; widespread from California and British Columbia eastward to North Dakota and Colorado. | Astragalus purshii var. purshii |
| 4 | Corollas purple or pink-purple throughout; British Columbia to s California (cis- and transmontane), sw Montana, and sc Nevada. | > 5 |
| 5 | Banners (14.6–)19–25(–26.5) mm; keel (11.5–)12.4–21(–22.5) mm. | > 6 |
| 6 | Plants acaulescent or subacaulescent; leaflets (5 or)7 or 9(or 11), blades obovate, obovate-cuneate, or broadly elliptic, apices obtuse or truncate; ec Idaho, sw Montana. | Astragalus purshii var. concinnus |
| 6 | Plants shortly caulescent or subacaulescent; leaflets (3 or)5–17(–21), blades obovate-cuneate, oblanceolate, narrowly elliptic or elliptic-oblanceolate, apices usually acute, subacute, or short-acuminate, rarely obtuse; British Columbia, California, Idaho, Nevada, Oregon, Utah, Washington. | > 7 |
| 7 | Legumes not or very shallowly sulcate ventrally; leaflets (3 or)5–13(–17), blades usually obovate-cuneate or oblanceolate, rarely elliptic-oblanceolate, apices usually acute or subacute, rarely obtuse; racemes 3–11-flowered; banners (14.6–)15.4–25 mm; cis- and transmontane California, w Nevada, and Oregon. | Astragalus purshii var. tinctus |
| 7 | Legumes strongly depressed-sulcate ventrally in proximal 1/2; leaflets (7 or)9–15(or 17), blades usually narrowly elliptic, rarely elliptic-oblanceolate, apices usually acute or short-acuminate; racemes 2–5(–10)-flowered; banners 19–25(–26.5) mm; Oregon and British Columbia eastward to Utah. | Astragalus purshii var. glareosus |
| 5 | Banners 11.5–18(–25) mm; keel 10.2–15(–20.8) mm. | > 8 |
| 8 | Legumes strongly sulcate ventrally in proximal 1/2; c Nevada. | Astragalus purshii var. pumilio |
| 8 | Legumes not or shallowly sulcate ventrally; ne California, sw Idaho, nw Nevada, se Oregon. | > 9 |
| 9 | Legumes 13–23(–27) mm; racemes with relatively short (subcapitate) flowering axes; ne California, nw Nevada, e Oregon. | Astragalus purshii var. tinctus |
| 9 | Legumes 8–13 mm; racemes with relatively long flowering axes; along Owyhee, Snake, and lower Bruneau rivers, se Oregon and sw Idaho. | Astragalus purshii var. ophiogenes |