Astragalus cusickii
Proc. Amer. Acad. Arts 13: 370. 1878.
Plants clump-forming, slender, 30–70 cm, strigulose; from subterranean or superficial caudex. Stems erect to ascending, strigulose. Leaves 4–10(–13) cm; stipules connate-sheathing and papery-membranous at proximal nodes, connate or distinct and herbaceous at distal nodes, 0.5–4.5 mm; leaflets 13–21, blades linear to linear-filiform, (5–)7–15(–17) mm, apex acute to obtuse, surfaces strigulose or adaxially glabrous; terminal leaflet sometimes decurrent distally, not jointed to rachis. Peduncles erect or incurved-ascending, 5–15(–22) cm. Racemes becoming loosely (3–)4–14(–18)-flowered; axis 1–8.5 cm in fruit; bracts 0.8–1.5 mm; bracteoles 0. Pedicels ascending, 1.2–3.5 mm. Flowers 12.5–15.5 mm; calyx campanulate, obliquely cuneate, 4–6.7 mm, silky-villous, hairs white, sometimes also black, tube 3.2–5.8 mm, lobes triangular, 0.5–1 mm; corolla white, creamy white, or purplish, banner recurved through 40°; keel 8–11 mm, apex bluntly deltate or triangular, often slightly beaklike. Legumes pale green, sometimes also red-mottled, becoming stramineous, straight or slightly curved, obliquely obovoid, semi-obovoid, or semi-ellipsoid, bladdery-inflated, 20–48 × 5–16(–22) mm, papery-membranous, translucent, apex differentiated into broad, low-deltoid beak, glabrous; stipe (5–)8–12 mm. Seeds 10–20.
Distribution
nw United States.
Discussion
Varieties 4 (4 in the flora).
Astragalus cusickii is known from the great canyons of the Snake and lower Salmon rivers and their tributaries; it is peripheral to the closely related, variable A. whitneyi, from which it differs conspicuously in its reduced foliage. The varieties of A. cusickii seem to have resulted from its geographical isolation and ability to adapt in various habitats.
Recent phylogenetic analysis indicates that three monophyletic entities exist within traditional Astragalus cusickii and justification exists to recognize each as a distinct species (J. F. Smith and J. C. Zimmers 2017; Zimmers et al. 2017). Two of the present varieties, vars. packardiae and sterilis, would become A. packardiae (Barneby) J. F. Smith & Zimmers and A. sterilis Barneby, respectively, with var. flexilipes maintained within A. cusickii.
Selected References
None.
Lower Taxa
Key
| 1 | Leaflets 9–15(or 17), blade surfaces glabrous adaxially; calyces 3.2–4.4 mm; legumes semi-obovoid or semi-ellipsoid, 6–12 mm wide when pressed; lower Salmon and Little Salmon rivers, Idaho and Adams counties, Idaho, Asotin County, Washington. | Astragalus cusickii var. flexilipes |
| 1 | Leaflets (5 or)7–11(or 13), blade surfaces usually strigulose (often densely so); calyces 3–5.8 mm; legumes usually broadly obovoid or obovoid-ellipsoid, rarely semi-ellipsoid, (1–)1.2–2.2 mm wide when pressed; Snake River canyon and streams affluent from the west, ne Oregon, immediately adjacent Idaho, and extreme se corner of Washington. | > 2 |
| 2 | Leaflets to 2–5 mm, terminal leaflet not jointed with rachis to slightly dilated; plants from subterranean caudex, sometimes with stolonlike branches; legumes purple-mottled; Owyhee County, Idaho, and Malheur County, Oregon. | Astragalus cusickii var. sterilis |
| 2 | Leaflets to 5–18(–27) mm, terminal leaflet jointed or continuous with rachises; plants from shallow subterranean or superficial caudex; legumes not or faintly mottled; wc Idaho, e Oregon (including Malheur County), and se Washington. | > 3 |
| 3 | Leaves foliose distally; calyces 4.4–5.8 mm; corollas white or creamy white, concolorous, banners 14–15.5 mm; legumes much inflated, 1–2 cm wide when pressed; Malheur County, Oregon, n on both sides of the Snake River to Asotin County, Washington. | Astragalus cusickii var. cusickii |
| 3 | Leaves reduced to naked rachis distally; calyces 3.7–4.3 mm; corollas purplish, banners 8.5–10.5 mm; legumes narrowly ellipsoid, 7–10 mm wide; Payette County, Idaho. | Astragalus cusickii var. packardiae |