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blackish locoweed, blackish oxytrope, one-flower oxytrope

Habit Plants pulvinate-cespitose to loosely matted, appearing acaulescent, herbage silvery-canescent, villous, silky-villous, strigose, pilose, or glabrous; caudex branches erect or ascending to prostrate-spreading.
Leaves

0.5–5 cm;

stipules membranous, whitish or with light tan or grayish herbaceous tips, 5–14 mm, usually ± pilose, rarely glabrous abaxially, margins often long-ciliate, with clavate processes;

leaflets 5–15, blades elliptic to ovate, 2–10 × 1–2(–3) mm, flat, margins involute but not falcate, apex acute or obtuse, surfaces silky- or silvery-canescent, villous, strigose, or loosely pilose, rarely glabrous.

Racemes

1 or 2(–5)-flowered.

Peduncles

0.3–4[–5] cm, pubescent;

bract narrowly lanceolate to linear, pilose.

Corollas

bright pink-purple or blue-purple to white, 12–20 mm.

Calyces

campanulate, usually black-pilose, sometimes villous, strigose, or glabrous;

tube 3–6 mm, lobes 1.8–4 mm.

Legumes

spreading, subsessile to short-stipitate or stipitate, stipe 1.5–5 mm, oblong-ellipsoid, 18–38(–40) × 8–11 mm, unilocular or subunilocular, usually strigulose to pilose or villous, rarely glabrous.

Oxytropis nigrescens

Distribution
from USDA
n North America; Asia
[WildflowerSearch map]
[BONAP county map]
Discussion

The Pan-Arctic Flora (http://panarcticflora.org/) splits the Oxytropis nigrescens complex into multiple species. It does not recognize O. nigrescens in the narrow sense as present in North America, restricting that species to Asia; instead, O. arctobia, O. bryophila and O. czukotica Jurtzev (not treated here) are considered present in North America. The Pan-Arctic Flora does not address the status of O. nigrescens var. lonchopoda because it grows outside the region they considered.

Varieties 3 (3 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Legumes long-stipitate, stipes 4–5 mm, subequal to calyx tube; Ogilvie Mountains, Yukon.
var. lonchopoda
1. Legumes subsessile to short-stipitate, stipes 1.5–2 mm, shorter than calyx tube; Alaska, British Columbia, Northwest Territories, Nunavut, Quebec, Yukon.
→ 2
2. Leaflets 9–15, blade surfaces silvery-canescent, villous, strigose, or glabrous; Alaska, British Columbia, Northwest Territories, Yukon.
var. nigrescens
2. Leaflets 5–11, blade surfaces densely silky-canescent; alpine in s Yukon and n British Columbia, coastal from Mackenzie Delta east­ward.
var. uniflora
Source FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae > Oxytropis
Sibling taxa
O. arctica, O. besseyi, O. borealis, O. campestris, O. deflexa, O. huddelsonii, O. kobukensis, O. kokrinensis, O. lagopus, O. lambertii, O. maydelliana, O. mertensiana, O. multiceps, O. nana, O. oreophila, O. parryi, O. podocarpa, O. riparia, O. scammaniana, O. sericea, O. splendens
Subordinate taxa
O. nigrescens var. lonchopoda, O. nigrescens var. nigrescens, O. nigrescens var. uniflora
Synonyms Astragalus nigrescens
Name authority (Pallas) Fischer in A. P. de Candolle and A. L. P. P. de Candolle: Prodr. 2: 278. (1825)
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