Astragalus purshii |
Astragalus obscurus |
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Pursh's milkvetch, woollypod milkvetch |
arcane milkvetch |
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Habit | Plants perennial, acaulescent to shortly caulescent, densely villous to villous-tomentose, hairs basifixed. | Plants perennial, caulescent, strigillose, hairs basifixed. |
Stems | prostrate, loosely to densely tufted, 0–20 cm. |
several–numerous, decumbent to ascending, 15–40 cm. |
Leaves | 1–12(17) cm; leaflets (3)5–17(21), elliptic to oblanceolate, 2–14(20) × 1–7 mm; tips obtuse to acute; surfaces densely villous; stipules 2.5–15 mm; free. |
(2.5)4–10(12) cm; leaflets 5–15, oblong-elliptic to lance-oblong or linear-elliptic, 2–15 × 0.5–2.5 mm; tips obtuse to truncate to shallowly retuse or subacute; surfaces abaxially strigillose, adaxially thinly pubescent to glabrous; stipules 1.5–2.5 mm; free. |
Inflorescences | racemes or subumbels, 1–12-flowered; peduncles 1–14 cm; bracts 4–9 mm; pedicels 2–4.3 mm; bracteoles 0–2. |
racemes compact in early anthesis; soon elongating; (3)6–15-flowered; peduncles 3–15 cm; bracts 0.8–2.5 mm; pedicels 0.5–2.2 mm; bracteoles 0–2. |
Flowers | ascending at anthesis; calyces 5.5–16(19) mm, often purple, villous-pilose with white or mixed white and black hairs; tubes 8.5–12.5 mm; teeth subulate, 2.2–6 mm; corollas 19–27 mm; whitish to ochroleucous or pink-purple; ovules 14–40(46). |
ascending at anthesis; calyces 3–5.5 mm, strigillose with black and white hairs; tubes 2.3–4 mm; teeth triangular to subulate, 0.4–1.6 mm; corollas 7–10.5 mm, ochroleucous or whitish, often tinged with dull purple; ovules 14–23. |
Fruits | unilocular, ascending, obliquely ovoid, usually curved, obcompressed, scarcely to deeply sulcate; (7)13–27(30) × 3.5–11 mm, densely white to tawny tomentose or densely villous; hairs nearly always concealing valve surfaces; valves coriaceous, sessile or on gynophores 0–1.6 mm. |
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Fruits ± | bilocular; erect, linear-oblong; straight, obtusely triquetrous, 10–25 × 2.4–4 mm, finely strigillose; valves coriaceous to cartilaginous; stipes 0. |
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Astragalus purshii |
Astragalus obscurus |
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Distribution | ||
Discussion | Western North America. ~8 varieties; 4 varieties treated in Flora. Throughout western North America, particularly in the Intermountain Region, this is a low, tufted milkvetch with white or gray villous hairs and pods resembling balls of cotton. Barneby (1964) stated, “Attempts to devise a practical key to the varieties of A. purshii are never wholly successful.” Variety ophiogenes, the Snake River milkvetch, a native of Idaho, has been reported from Malheur County, but this is apparently based on misidentifications of A. purshii var. lagopinus. Variety ophiogenes has 3–11-flowered racemes and 9–17 leaflets. |
Sagebrush, ridge tops, talus, hillsides, scabland. Flowering May–Jul. 700–2300 m. BR, BW, ECas, Lava, Owy. CA, ID, NV. Native. Astragalus obscurus is recognizable by its few leaflets, small, dingy flowers ascending in a close raceme, and erect, sessile, linear-oblong, trigonously compressed fruits. It may be confused with the sympatric A. atratus, which is alike in general habit but has pendulous, decurved pods. |
Source | Flora of Oregon, volume 2, page 671 Richard Halse |
Flora of Oregon, volume 2, page 670 Richard Halse |
Sibling taxa | ||
Subordinate taxa | ||
Synonyms | Astragalus purshii var. ophiogenes | Astragalus miser |
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