Flora of North America species comparison

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Oxytropis nigrescens var. uniflora

Oxytropis
Photo is of parent taxon

one-flower blackish locoweed, one-flower oxytrope

crazyweed, locoweed, oxytrope
Habit Plants densely cespitose or pulvinate, herbage densely silky-villous, caudex branches often becoming columnar. Herbs, perennial, usually with very short internodes and appearing acaulescent, rarely caulescent, with 1 or more internodes apparent, unarmed or with spinescent leaf bases; usually cespitose, rarely pulvinate-cespitose or loosely matted; sometimes glandular-viscid, pubescent, hairs usually basifixed (malpighian in O. lambertii); from taproot or caudex.
Stems

spreading to ascending, usually pubescent, rarely glabrescent or glabrous.
Leaves

basally clustered or cauline, alternate, mostly odd-pinnate;

stipules present, sometimes persistent, adnate to petiole, often connate-sheathing;

petiolate, petiole sometimes persistent as marcescent thatch on caudex, rarely as pungent spines;

leaflets 1–45(–70), usually opposite, subopposite, scattered (irregularly spaced), or fasciculate, rarely alternate or verticillate, usually jointed to rachis, blade margins entire, surfaces usually pubescent, sometimes glabrous.
Leaflets

5–11, blade surfaces densely silky-canescent.

Racemes

1- or 2-flowered.

Inflorescences

1–50-flowered, axillary, racemes (sometimes subcapitate);

bract 1;

bracteoles usually absent, rarely 2.
Peduncles

0.3–2.1 cm.

Flowers

papilionaceous;

calyx usually campanulate or cylindric, rarely inflated-urceolate, lobes 5, sometimes inflated and enclosing legumes, usually ruptured by legume;

corolla pink to blue-purple or white to yellowish, 5–25 mm, keel petals shorter than wing petals, tip elongated into porrect beak;

stamens 10, diadelphous;

anthers dorsifixed;

ovary enclosed in staminal sheath;

style glabrous.
Fruits

legumes, sessile or stipitate, sometimes tumid or bladdery-inflated, straight, oblong to ellipsoid, ovoid, ovoid-ellipsoid, ovoid-oblong, lanceoloid-ovoid, cylindric, or subcylindric, abaxial suture usually rounded, adaxial suture often sulcate, dehiscent apically or throughout, unilocular or bilocular, or partially bilocular by intrusion of adaxial suture, usually pubescent, rarely glabrous.
Legumes

usually subsessile, sometimes short-stipitate, stipe to 2 mm, shorter than calyx tube;

body usually variously strigulose to pilose or villous, rarely glabrous, hairs black.

Seeds

3–25, light to dark brown or black, somewhat reniform.
x

= 8.

Oxytropis nigrescens var. uniflora

Oxytropis
Phenology Flowering summer.
Habitat Arctic tundra, coastal shores, gravel bars, rock outcrops.
Elevation 10–1500 m. (0–4900 ft.)
Distribution
from FNA
AK; BC; NT; NU; QC; YT
[BONAP county map]
from USDA
North America; Europe; Asia
[BONAP county map]
Discussion

Variety uniflora, as treated here, is a North American endemic and is of conservation concern in British Columbia; it was treated as Oxytropis arctobia by Z. Meyer (2012). Oxytropis gorodkovii Jurtzev from the Chukchi Peninsula of the Russian Far East matches it in every way. The Siberian specimens seem to represent ecological variants within var. nigrescens. The online Pan-Arctic Flora (http://panarcticflora.org/) considers the material treated here as var. uniflora to be two distinct species: O. gorodkovii and O. arctobia.

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

Species ca. 300 (22 in the flora).

Separation of Oxytropis from Astragalus has long been argued, and the history of the discussion was outlined by R. C. Barneby (1952b) and S. L. Welsh (1989). The main distinctions lie in the inequilateral leaf bases of Oxytropis (as opposed to equilateral in Astragalus), and the porrect keel petals found in all species of Oxytropis and not in Astragalus. Molecular phylogenetic studies have supported the distinctness of the two genera (M. F. Wojciechowski 2005; A. D. Tekpinar et al. 2016).

Several relatively recent treatments of the taxonomy and nomenclature of Oxytropis differ greatly in their conclusions. Among these are the revision by S. L. Welsh (2001), publications by B. A. Jurtzev (1986, 1993b), J. M. Gillett et al. (2007), and the Pan-Arctic Flora (http://panarcticflora.org/).

At least some species of Oxytropis are highly toxic to grazing animals, due to the presence of swainsonine in their tissues (L. F. James et al. 1989).

Oxytropis revoluta Ledebour was attributed to Alaska by E. Hultén (1968) but has not yet been found in the flora area. It occurs in Russian islands immediately west of the United States/Russia border.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Plants usually caulescent (1+ internodes apparent); legumes subsessile or stipitate, pendulous or spreading-declined.
→ 2
2. Leaflets 11–17, blades broadly lanceolate to oblanceolate, apices acute or subacute; racemes 20–40-flowered; introduced, Idaho, Montana, North Dakota, Utah, Wyoming.
O. riparia
2. Leaflets (9–)15–41, blades ovate, lanceolate, or lanceolate-oblong, apices acute to obtuse; racemes (2–)4–25[–30+]-flowered; native, widespread in w North America.
O. deflexa
1. Plants acaulescent or appearing acaulescent (internodes concealed by leaf bases); legumes sessile, subsessile, or stipitate, erect, spreading, or spreading-declined.
→ 3
3. Legumes spreading-declined.
O. deflexa
3. Legumes erect or spreading.
→ 4
4. Base of herb sheathed with reddish, purplish, or purplish brown stipules.
→ 5
5. Corollas yellowish.
O. maydelliana
5. Corollas purplish.
→ 6
6. Racemes 1–3-flowered; legumes stipitate, reclining on ground at maturity, usually at least 3 times longer than wide.
O. kokrinensis
6. Racemes 5–8-flowered; legumes sessile, held aloft at maturity, to 3 times longer than wide.
O. kobukensis
4. Base of herb with light tan or grayish stipules, sometimes black in O. campestris).
→ 7
7. Leaflets usually 1 or 3, rarely 5, decurrent or obscurely articulated with rachis.
O. mertensiana
7. Leaflets (1–)5–45(–70), jointed to rachis.
→ 8
8. Plants glandular-viscid (especially stipules and calyces); bracts glabrous, except margins ciliate.
O. borealis
8. Plants not glandular-viscid; bracts pilose or villous.
→ 9
9. Racemes usually 1–5-flowered; corollas pink, purple, or bluish, not yellow, ochro­leucous, or white (except in white morphs).
→ 10
10. Corollas (14–)16–22 mm; leaflets 9+, alternate, opposite, subopposite, widely scattered, or fasciculate; stipular margins with clavate processes mixed with cilia.
O. arctica
10. Corollas 6–20(–24) mm; leaflets 5–17, widely scattered or opposite, not fasciculate; stipular margins ciliate, without clavate processes (except in some O. nigrescens).
→ 11
11. Legumes erect, usually black-pilose, rarely glabrous or white-pilose; stipules usually prominent, glabrous or sparsely pilose abaxially, stramineous; interior Alaska, Yukon, Northwest Territories, British Columbia.
O. scammaniana
11. Legumes spreading to ascending, glabrous or pilosulous; stipules not especially conspicuous, pilose, silky-pilose, villous, or glabrous abaxially, whitish to light tan, grayish, or black; widespread.
→ 12
12. Calyces usually conspicuously swollen or inflated at anthesis, investing legumes or nearly so (if not conspicuously inflated, O. lagopus var. atropurpurea, calyx villous to shaggy-villous); Alberta, Colorado, Idaho, Montana, Nebraska, South Dakota, Utah, Wyoming.
→ 13
13. Legumes strigose-canescent, leathery, rigid at maturity; Wyoming.
O. nana
13. Legumes villous, papery, not rigid at maturity; Alberta, Colorado, Idaho, Montana, Nebraska, South Dakota, Utah, Wyoming.
→ 14
14. Bracts ovate to broadly lanceolate, flat; plants pulvinate-cespitose; Colorado, Nebraska, Utah, Wyoming.
O. multiceps
14. Bracts ovate-lanceolate to lanceolate, margins involute; plants cespitose but not pulvinate; Alberta, Idaho, Montana, South Dakota, Wyoming.
O. lagopus
12. Calyces slightly inflated at anthesis, not investing legume at maturity; n Canada to sw United States.
→ 15
15. Legumes 10–18(–23) mm, sessile or subsessile, glabrous or minutely strigose or strigulose, unilocular; racemes 1 or 2 (or 3)-flowered; Alaska, British Columbia, Yukon.
O. huddelsonii
15. Legumes (7–)9–38(–40) mm, sessile, subsessile, or stipitate, usually pilose, pilosulous, villous, villous-pilose, hirtellous, strigulose, or strigose-pilosulous, rarely glabrous, unilocular, subunilocular, sub-bilocular, or bilocular; racemes 1–12-flowered; widespread.
→ 16
16. Legumes ovoid-ellipsoid or bladdery-inflated, stipitate; leaflet blades falcate.
O. podocarpa
16. Legumes oblong, oblong-ellipsoid, lanceoloid-ovoid, ovoid, or bladdery-inflated, usually sessile, subsessile, or short-stipitate (stipitate in O. nigrescens var. lonchopoda); leaflet blades not falcate.
→ 17
17. Corollas 12–20 mm; leaflet surfaces usually silky- or silvery-canescent, villous, strigose, or loosely pilose, rarely glabrous; n North America.
O. nigrescens
17. Corollas usually 6–12.5 mm (to 17 mm in O. oreophila var. jonesii); leaflet surfaces pilose, villous-pilose, or silky-pilose; w United States.
→ 18
18. Racemes 3–5-flowered; legumes ellipsoid, cylindroid, bladdery-inflated.
O. oreophila
18. Racemes 1–3 (or 4)-flowered; legumes oblong to lanceoloid-ovoid or ovoid, not bladdery-inflated.
O. parryi
9. Racemes usually 6–many-flowered; corollas pink, pink-purple, lavender, bluish purple, blue, purple, pinkish violet, if racemes fewer-flowered, then corollas yellow, ochroleucous, or white.
→ 19
19. Hairs malpighian; corollas usually pink-purple, rarely white.
O. lambertii
19. Hairs basifixed; corollas pink, pink-purple, lavender, bluish purple, blue, purple, pinkish violet, white, whitish, yellowish, or creamy white.
→ 20
20. Corollas usually 6–12.5 mm (to 17 mm in var. jonesii); legumes bladdery-inflated; Arizona, California, Nevada, Utah.
O. oreophila
20. Corollas (10–)12–27(–28) mm; legumes cylindric, subcylindric, ovoid, ovoid-oblong, or ovoid-acuminate, not bladdery-inflated; Canada, w United States, not including Arizona or California.
→ 21
21. Calyces swollen at anthesis, accrescent and enclosing fruit.
→ 22
22. Calyces villous to shaggy-villous, hairs mixed blackish and white, appearing gray; legumes villous, papery to nearly membranous; Alberta, Idaho, Montana, South Dakota, Wyoming.
O. lagopus
22. Calyces densely shaggy-hirsute and subtomentose, hairs white; legumes strigose-canescent, firm; Wyoming.
O. nana
21. Calyces not or slightly swollen in fruit, usually ruptured by fruit.
→ 23
23. Corollas white or yellowish.
→ 24
24. Corollas (10–)12–20(–23) mm; leaflets 7–45; legumes papery to leath­ery or membranous.
O. campestris
24. Corollas (14–)16–27(–28) mm; leaflets 7–19(–21); legumes fleshy when fresh, becoming leathery or almost woody and rigid, or thinly papery.
→ 25
25. Leaflets 7–19(–21), blade surfaces sericeous, often densely so; racemes subcapitate to elongate, 5–20+-flowered; legumes fleshy when fresh, becoming leathery or almost woody and rigid.
O. sericea
25. Leaflets 11–17, blade surfaces pilose; racemes relatively short to subcapitate, 2–10-flowered; legumes thinly papery.
O. arctica
23. Corollas pinkish or purplish (rarely creamy white in O. splendens).
→ 26
26. Calyces with blackish hairs and long, white hairs, appearing gray; leaves 1–10 cm; Alberta, Idaho, Montana, South Dakota, Wyoming.
O. lagopus
26. Calyces with white hairs, if with both blackish and white, then not from Wyoming or adjacent states; leaves 1.5–28 cm; Alaska east to Newfoundland and Labrador, south to New Mexico.
→ 27
27. Corollas 17–25 mm; stipules papery or membranous, light tan or pale gray; Colorado, Idaho, Montana, Nevada, Saskatchewan, Utah, Wyoming.
O. besseyi
27. Corollas 11–22(–23) mm; stipules rigid, fragile, or membranous, purplish, yellowish, or grayish; widespread.
→ 28
28. Corollas (14–)16–22 mm; stipular margins ciliate, with clavate processes; n, w Alaska, Manitoba, Northwest Territories, Nunavut, Yukon.
→ 29
29. Stipules firm, usually purplish, usually well separated on elongate caudex branches; leaflets not fasciculate; Kobuk River drainage, Alaska.
O. kobukensis
29. Stipules fragile, grayish or yellowish, strongly imbricate; leaflets usually fasciculate; Alaska, Manitoba, Northwest Territories, Nunavut, Yukon.
O. arctica
28. Corollas 11–20(–23) mm; stipular margins ciliate or not, with or without clavate processes; n, nw North America, seldom in arctic.
→ 30
30. Leaflets fasciculate or not; corollas 11–20(–23) mm, calyces tubes (3.7–)4–9 mm; stipules glabrous, strigose, or pilose abaxially becoming glabrate, with or without marginal clavate processes; Alaska, se, n Yukon, Alberta, n, c British Columbia, North Dakota.
O. campestris
30. Leaflets usually fasciculate, rarely verticillate; corollas 12–16 mm, calyces tubes 5–6.5 mm; stipules silky-pilose abaxially, without marginal clavate processes; e Alaska, s Yukon, e to Hudson Bay, s to Colorado.
O. splendens
Source FNA vol. 11. FNA vol. 11. Author: Stanley L. Welsh.
Parent taxa Fabaceae > subfam. Faboideae > Oxytropis > Oxytropis nigrescens Fabaceae > subfam. Faboideae
Sibling taxa
O. nigrescens var. lonchopoda, O. nigrescens var. nigrescens
Subordinate 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. nigrescens, O. oreophila, O. parryi, O. podocarpa, O. riparia, O. scammaniana, O. sericea, O. splendens
Synonyms O. arctica var. uniflora, Astragalus nigrescens var. arctobia, O. arctobia, O. nigrescens subsp. arctobia, O. nigrescens var. arctobia, Spiesia arctobia
Name authority (Hooker) Barneby: Proc. Calif. Acad., ser. 4, 27: 209. (1952) de Candolle: Astragalogia (qto.), 24, 66; (fol.), 19, 53, plates 2–8. (1802) — name conserved
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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