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Robbins' milk-vetch

kremmling milkvetch, Osterhout's milkvetch

Habit Plants clump-forming, slender to robust, 7–45(–60) cm, strigulose to pilose-villosulous; from superficial or somewhat subterranean caudex. Plants stout, clump-forming, 25–45 cm, very sparsely strigulose; from shallow, subterranean caudex.
Stems

usually ascending, rarely decumbent, 0–2 cm underground, strigulose to pilose-villosulous.

erect or ascending, very sparsely strigulose.

Leaves

2.5–12 cm;

stipules 1.5–6 mm, papery at proximal nodes, herbaceous or submembranous at distal nodes;

leaflets (5 or)7–17, blades lanceolate to oblong, (3–)5–30(–32) mm, apex obtuse or emarginate, surfaces usually strigulose, sometimes villous-pilosulous, cinereous, glabrate, or glabrous abaxially, glabrous, glabrescent, or sparsely strigose adaxially.

sometimes unifoliolate distally, 3–8.5 cm;

stipules shortly connate-sheathing and scarious at proximal nodes, connate or distinct and herbaceous at distal nodes, 2–8 mm;

leaflets (1 or)5–15, blades linear-oblong, oblanceolate, or filiform, 6–40 mm, apex obtuse to acute, surfaces glabrous or sparsely strigulose abaxially, glabrous adaxially;

terminal leaflet decurrent, not jointed to rachis.

Racemes

(3–)5–25(–33)-flowered;

axis 1–18(–20) cm in fruit, elongating little after flowering, arising distal to middle of stem;

bracts 1–3.5 mm;

bracteoles usually 0.

12–25-flowered, flowers spreading-declined;

axis 2.5–10 cm in fruit;

bracts 1–3.5 mm;

bracteoles 1 or 2.

Peduncles

incurved-ascending or erect, 3.5–21(–23) cm, usually surpassing subtending leaf, together with racemes usually shorter than stems.

erect, (6–)8–14 cm.

Pedicels

0.5–3 mm.

2–6 mm.

Flowers

(6–)7.2–11.5 mm;

calyx 4–6.8 mm, strigulose, tube 3.2–4.5 mm, lobes subulate, 0.7–2.3 mm;

corolla usually purple, pink-purple, pink, lilac, lavender, or whitish, sometimes whitish with maculate keel;

wing apex obtuse;

keel 5.4–7.9 mm, shorter than wings.

17–23 mm;

calyx 8.5–12 mm, strigulose, tube 7–10 × 3.5–4.7 mm, lobes triangular-subulate, 0.8–2 mm;

corolla white;

keel 12.3–14.8 mm.

Legumes

pendulous, green or purplish, straight or slightly decurved, ellipsoid, obtusely 3-sided, faces slightly convex, flattened or depressed but not sulcate abaxially, 13–25 × 3.5–5.5 mm, subunilocular or semibilocular, papery-membranous, sparsely strigulose, hairs black or black and white;

valves inflexed as hyaline septum 0.2–2 mm wide;

stipe (0.5–)1.5–6.5 mm.

pendulous, green-stramineous, straight or slightly incurved, linear-ellipsoid, strongly laterally compressed, 25–45 × 3–4 mm, fleshy becoming stiffly papery, glabrous;

stipe 2–6.5 mm.

Seeds

6–11.

12–17.

Astragalus robbinsii

Astragalus osterhoutii

Phenology Flowering Jun–Aug.
Habitat Seleniferous clay hills, bar­ren knolls, bluffs on openings in sagebrush-grass com­munities, under sagebrush.
Elevation 2200–2400 m. (7200–7900 ft.)
Distribution
from USDA
North America
[WildflowerSearch map]
[BONAP county map]
from FNA
CO
[BONAP county map]
Discussion

Varieties 8 (8 in the flora).

Astragalus robbinsii consists of a series of infraspecific taxa with two centers of dispersal in North America: Colorado to Alaska, and New England into eastern Canada. The distribution of three closely allied subordinate taxa within Vermont and New Hampshire is unmatched in the genus in North America. D. Isely (1998) questioned the taxonomic significance of the traditional varieties as recognized herein. The species is often confused in herbaria with A. alpinus, which has a keel longer than or as long as and wider than the wings (in A. robbinsii the keel is shorter than and little or no wider than the wings).

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

Astragalus osterhoutii, with the combination of white flowers and stipitate, laterally compressed, ultimately deflexed and proportionally very long fruits, is unique in sect. Pectinati. This selenophyte, restricted to Grand County, was estimated to have a geographic range of approximately 120 km2 in soils derived from shales of the Niobrara, Pierre, and Troublesome formations (S. Spackman et al. 1997b). J. D. Karron (1989) reported this species as self-compatible, but not particularly autogamous. It was reported to have restricted genetic polymorphism, but still to exhibit a moderate level of isozyme variation (Karron et al. 1988).

Astragalus osterhoutii is in the Center for Plant Conservation’s National Collection of Endangered Plants.

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

Key
1. Leaflet blade surfaces abaxially densely gray or white villous-pilosulous, hairs 0.6–0.8 mm; legume stipes 1.2–3 mm, septae 1.2–2 mm wide; s coastal Alaska.
var. harringtonii
1. Leaflet blade surfaces abaxially sparsely strigu­lose, cinereous, glabrous, or glabrate, hairs 0.2–0.6(–0.7) mm; legume stipes (0.5–)1.5–5(–6.5) mm, septae 0.2–1(–1.5) mm wide; not in s coastal Alaska.
→ 2
2. Legume stipes (1–)1.5–5(–6.5) mm; Alaska, New England, Nova Scotia, n Rocky Mountains.
→ 3
3. Stems 7–10 cm; racemes 5–11-flowered, axes 1–1.5 cm in fruit (barely elongated); legume stipes 5 mm; seeds 5 or 6; Mt. Roberts, near Juneau, Alaska.
var. morganiae
3. Stems 10–40(–60) cm; racemes (5–)7–21-flowered, axes (1–)3–18(–20) cm in fruit; legume stipes (1–)1.5–5(–6.5) mm; seeds (6 or)7–11.
→ 4
4. Legumes 10–15 mm, sparsely strigu­lose, beaks to 1 mm; corollas whitish; Vermont historically.
var. robbinsii
4. Legumes (10–)13–25 mm, sparsely or densely pubescent, beaks 0.8–3 mm; corollas pale purple, pink-purple, pink, or whitish and keel tip purple; widespread, including Vermont.
→ 5
5. Legumes sparsely strigose-pilosulous, beaks 0.8–1.5 mm; leaf­let blade surfaces uniformly strigu­lose abaxially, or glabrate through­out; Alaska, Canada, w United States, Maine and Vermont.
var. minor
5. Legumes sparsely strigulose, beaks 1.5–3 mm; leaflet blade surfaces cinereous abaxially, pubescent adax­ially (margins sparsely pubescent); local along Connecticut River in Vermont and New Hampshire.
var. jesupii
2. Legume stipes 0.5–3(–6.5) mm; coastal Labrador, adjoining Newfoundland, e Quebec to Alberta, northward to Northwest Territories, southward to New Mexico, including Maine and Vermont.
→ 6
6. Seeds 3–6; legumes 8–13 mm; Wallowa Mountains, ne Oregon.
var. alpiniformis
6. Seeds (6 or)7–10; legumes (8–)10–25 mm; not Oregon.
→ 7
7. Raceme axis 1.2–6(–8) cm in fruit; leaflet blade surfaces sparsely pubescent along margins adaxially or strigulose throughout; s Labrador, adjoining Newfoundland, Quebec.
var. fernaldii
7. Raceme axis (2–)3–18(–20) cm in fruit; leaflet blade surfaces glabrous or glabrate adaxially; not s Labrador, adjoining Newfoundland, and Quebec.
→ 8
8. Legumes (10–)13–25 mm, stipes (1–)1.5–5(–6.5) mm; racemes (5–)7–25(–33)-flowered, axes (2–)3–18(–20) cm in fruit; proximal stipules distinct or obscurely connate; not ne Nevada.
var. minor
8. Legumes (8–)10–15(–18) mm, stipes 0.5–1.4 mm; racemes remotely (3–)6–12-flowered, axes (2–)6–15 mm in fruit; proximal stipules connate 1/2 their length; East Humboldt and Ruby mountains, ne Nevada.
var. occidentalis
Source FNA vol. 11. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae > Astragalus > sect. Oroboidei Fabaceae > subfam. Faboideae > Astragalus > sect. Pectinati
Sibling taxa
A. accidens, A. accumbens, A. ackermanii, A. acutirostris, A. adanus, A. aequalis, A. agnicidus, A. agrestis, A. albens, A. albulus, A. allochrous, A. alpinus, A. altus, A. alvordensis, A. amblytropis, A. americanus, A. amnis-amissi, A. amphioxys, A. ampullarioides, A. ampullarius, A. andersonii, A. anisus, A. anserinus, A. applegatei, A. aquilonius, A. aretioides, A. argophyllus, A. aridus, A. arizonicus, A. arrectus, A. arthurii, A. asclepiadoides, A. asotinensis, A. asymmetricus, A. atratus, A. atropubescens, A. atwoodii, A. austiniae, A. australis, A. barnebyi, A. barrii, A. beathii, A. beatleyae, A. beckwithii, A. bernardinus, A. bibullatus, A. bicristatus, A. bisulcatus, A. bodinii, A. bolanderi, A. bourgovii, A. brandegeei, A. brauntonii, A. brazoensis, A. breweri, A. californicus, A. callithrix, A. calycosus, A. camptopus, A. canadensis, A. caricinus, A. casei, A. castaneiformis, A. castetteri, A. ceramicus, A. cerussatus, A. chamaeleuce, A. chamaemeniscus, A. chinensis, A. chloödes, A. chuskanus, A. cibarius, A. cicer, A. cimae, A. claranus, A. clevelandii, A. cliffordii, A. cobrensis, A. coccineus, A. collinus, A. coltonii, A. columbianus, A. concordius, A. congdonii, A. conjunctus, A. consobrinus, A. contortuplicatus, A. convallarius, A. cottamii, A. crassicarpus, A. cremnophylax, A. cronquistii, A. crotalariae, A. curtipes, A. curvicarpus, A. cusickii, A. cutleri, A. cyaneus, A. cymboides, A. deanei, A. debequaeus, A. desereticus, A. desperatus, A. deterior, A. detritalis, A. diaphanus, A. didymocarpus, A. distortus, A. diversifolius, A. douglasii, A. drabelliformis, A. drummondii, A. duchesnensis, A. eastwoodiae, A. egglestonii, A. emoryanus, A. endopterus, A. ensiformis, A. episcopus, A. equisolensis, A. eremiticus, A. ertterae, A. eucosmus, A. eurekensis, A. eurylobus, A. falcatus, A. feensis, A. filipes, A. flavus, A. flexuosus, A. fucatus, A. funereus, A. gambelianus, A. geyeri, A. gibbsii, A. giganteus, A. gilensis, A. gilmanii, A. gilviflorus, A. glycyphyllos, A. gracilis, A. grayi, A. gypsodes, A. hallii, A. hamiltonii, A. harrisonii, A. heilii, A. henrimontanensis, A. holmgreniorum, A. hoodianus, A. hornii, A. howellii, A. humillimus, A. humistratus, A. hyalinus, A. hypoxylus, A. inflexus, A. insularis, A. inversus, A. inyoensis, A. iodanthus, A. iodopetalus, A. iselyi, A. jaegerianus, A. jejunus, A. johannis-howellii, A. kelseyae, A. kentrophyta, A. kerrii, A. knightii, A. laccoliticus, A. lancearius, A. laxmannii, A. layneae, A. leibergii, A. lemmonii, A. lentiformis, A. lentiginosus, A. leptaleus, A. leptocarpus, A. leucolobus, A. limnocharis, A. lindheimeri, A. linifolius, A. loanus, A. lonchocarpus, A. lotiflorus, A. lutosus, A. lyallii, A. macrodon, A. magdalenae, A. malacoides, A. malacus, A. megacarpus, A. michauxii, A. microcymbus, A. microcystis, A. microlobium, A. micromerius, A. miguelensis, A. minthorniae, A. misellus, A. miser, A. missouriensis, A. moencoppensis, A. mohavensis, A. mollissimus, A. molybdenus, A. monoensis, A. montii, A. monumentalis, A. mulfordiae, A. multiflorus, A. musiniensis, A. naturitensis, A. neglectus, A. nelsonianus, A. neomexicanus, A. nevinii, A. newberryi, A. nidularius, A. nothoxys, A. nudisiliquus, A. nutans, A. nutriosensis, A. nuttallianus, A. nuttallii, A. nutzotinensis, A. nyensis, A. obcordatus, A. obscurus, A. oniciformis, A. oocalycis, A. oocarpus, A. oophorus, A. oreganus, A. osterhoutii, A. oxyphysus, A. pachypus, A. palmeri, A. panamintensis, A. pardalinus, A. parryi, A. pattersonii, A. pauperculus, A. paysonii, A. peckii, A. pectinatus, A. perianus, A. phoenix, A. pictiformis, A. pinonis, A. piscator, A. piutensis, A. plattensis, A. platytropis, A. polaris, A. pomonensis, A. porrectus, A. praelongus, A. preussii, A. proimanthus, A. proximus, A. pseudiodanthus, A. pterocarpus, A. pubentissimus, A. pulsiferae, A. puniceus, A. purshii, A. pycnostachyus, A. racemosus, A. rafaelensis, A. rattanii, A. ravenii, A. recurvus, A. reflexus, A. remotus, A. reventiformis, A. reventus, A. riparius, A. ripleyi, A. rusbyi, A. sabulonum, A. sabulosus, A. salmonis, A. saurinus, A. scaphoides, A. schmolliae, A. sclerocarpus, A. scopulorum, A. sepultipes, A. serenoi, A. sericoleucus, A. serpens, A. sesquiflorus, A. sheldonii, A. shevockii, A. shortianus, A. siliceus, A. simplicifolius, A. sinuatus, A. solitarius, A. sophoroides, A. soxmaniorum, A. spaldingii, A. sparsiflorus, A. spatulatus, A. speirocarpus, A. straturensis, A. striatiflorus, A. subcinereus, A. subvestitus, A. succumbens, A. tegetarioides, A. tener, A. tennesseensis, A. tephrodes, A. terminalis, A. tetrapterus, A. thurberi, A. tibetanus, A. tidestromii, A. tiehmii, A. titanophilus, A. toanus, A. toquimanus, A. tortipes, A. traskiae, A. tricarinatus, A. trichopodus, A. tridactylicus, A. troglodytus, A. tweedyi, A. tyghensis, A. umbellatus, A. umbraticus, A. uncialis, A. utahensis, A. vaccarum, A. vallaris, A. vexilliflexus, A. villosus, A. wardii, A. waterfallii, A. webberi, A. welshii, A. wetherillii, A. whitneyi, A. williamsii, A. wingatanus, A. wittmannii, A. woodruffii, A. wootonii, A. wrightii, A. xiphoides, A. yoderwilliamsii, A. zionis
A. accidens, A. accumbens, A. ackermanii, A. acutirostris, A. adanus, A. aequalis, A. agnicidus, A. agrestis, A. albens, A. albulus, A. allochrous, A. alpinus, A. altus, A. alvordensis, A. amblytropis, A. americanus, A. amnis-amissi, A. amphioxys, A. ampullarioides, A. ampullarius, A. andersonii, A. anisus, A. anserinus, A. applegatei, A. aquilonius, A. aretioides, A. argophyllus, A. aridus, A. arizonicus, A. arrectus, A. arthurii, A. asclepiadoides, A. asotinensis, A. asymmetricus, A. atratus, A. atropubescens, A. atwoodii, A. austiniae, A. australis, A. barnebyi, A. barrii, A. beathii, A. beatleyae, A. beckwithii, A. bernardinus, A. bibullatus, A. bicristatus, A. bisulcatus, A. bodinii, A. bolanderi, A. bourgovii, A. brandegeei, A. brauntonii, A. brazoensis, A. breweri, A. californicus, A. callithrix, A. calycosus, A. camptopus, A. canadensis, A. caricinus, A. casei, A. castaneiformis, A. castetteri, A. ceramicus, A. cerussatus, A. chamaeleuce, A. chamaemeniscus, A. chinensis, A. chloödes, A. chuskanus, A. cibarius, A. cicer, A. cimae, A. claranus, A. clevelandii, A. cliffordii, A. cobrensis, A. coccineus, A. collinus, A. coltonii, A. columbianus, A. concordius, A. congdonii, A. conjunctus, A. consobrinus, A. contortuplicatus, A. convallarius, A. cottamii, A. crassicarpus, A. cremnophylax, A. cronquistii, A. crotalariae, A. curtipes, A. curvicarpus, A. cusickii, A. cutleri, A. cyaneus, A. cymboides, A. deanei, A. debequaeus, A. desereticus, A. desperatus, A. deterior, A. detritalis, A. diaphanus, A. didymocarpus, A. distortus, A. diversifolius, A. douglasii, A. drabelliformis, A. drummondii, A. duchesnensis, A. eastwoodiae, A. egglestonii, A. emoryanus, A. endopterus, A. ensiformis, A. episcopus, A. equisolensis, A. eremiticus, A. ertterae, A. eucosmus, A. eurekensis, A. eurylobus, A. falcatus, A. feensis, A. filipes, A. flavus, A. flexuosus, A. fucatus, A. funereus, A. gambelianus, A. geyeri, A. gibbsii, A. giganteus, A. gilensis, A. gilmanii, A. gilviflorus, A. glycyphyllos, A. gracilis, A. grayi, A. gypsodes, A. hallii, A. hamiltonii, A. harrisonii, A. heilii, A. henrimontanensis, A. holmgreniorum, A. hoodianus, A. hornii, A. howellii, A. humillimus, A. humistratus, A. hyalinus, A. hypoxylus, A. inflexus, A. insularis, A. inversus, A. inyoensis, A. iodanthus, A. iodopetalus, A. iselyi, A. jaegerianus, A. jejunus, A. johannis-howellii, A. kelseyae, A. kentrophyta, A. kerrii, A. knightii, A. laccoliticus, A. lancearius, A. laxmannii, A. layneae, A. leibergii, A. lemmonii, A. lentiformis, A. lentiginosus, A. leptaleus, A. leptocarpus, A. leucolobus, A. limnocharis, A. lindheimeri, A. linifolius, A. loanus, A. lonchocarpus, A. lotiflorus, A. lutosus, A. lyallii, A. macrodon, A. magdalenae, A. malacoides, A. malacus, A. megacarpus, A. michauxii, A. microcymbus, A. microcystis, A. microlobium, A. micromerius, A. miguelensis, A. minthorniae, A. misellus, A. miser, A. missouriensis, A. moencoppensis, A. mohavensis, A. mollissimus, A. molybdenus, A. monoensis, A. montii, A. monumentalis, A. mulfordiae, A. multiflorus, A. musiniensis, A. naturitensis, A. neglectus, A. nelsonianus, A. neomexicanus, A. nevinii, A. newberryi, A. nidularius, A. nothoxys, A. nudisiliquus, A. nutans, A. nutriosensis, A. nuttallianus, A. nuttallii, A. nutzotinensis, A. nyensis, A. obcordatus, A. obscurus, A. oniciformis, A. oocalycis, A. oocarpus, A. oophorus, A. oreganus, A. oxyphysus, A. pachypus, A. palmeri, A. panamintensis, A. pardalinus, A. parryi, A. pattersonii, A. pauperculus, A. paysonii, A. peckii, A. pectinatus, A. perianus, A. phoenix, A. pictiformis, A. pinonis, A. piscator, A. piutensis, A. plattensis, A. platytropis, A. polaris, A. pomonensis, A. porrectus, A. praelongus, A. preussii, A. proimanthus, A. proximus, A. pseudiodanthus, A. pterocarpus, A. pubentissimus, A. pulsiferae, A. puniceus, A. purshii, A. pycnostachyus, A. racemosus, A. rafaelensis, A. rattanii, A. ravenii, A. recurvus, A. reflexus, A. remotus, A. reventiformis, A. reventus, A. riparius, A. ripleyi, A. robbinsii, A. rusbyi, A. sabulonum, A. sabulosus, A. salmonis, A. saurinus, A. scaphoides, A. schmolliae, A. sclerocarpus, A. scopulorum, A. sepultipes, A. serenoi, A. sericoleucus, A. serpens, A. sesquiflorus, A. sheldonii, A. shevockii, A. shortianus, A. siliceus, A. simplicifolius, A. sinuatus, A. solitarius, A. sophoroides, A. soxmaniorum, A. spaldingii, A. sparsiflorus, A. spatulatus, A. speirocarpus, A. straturensis, A. striatiflorus, A. subcinereus, A. subvestitus, A. succumbens, A. tegetarioides, A. tener, A. tennesseensis, A. tephrodes, A. terminalis, A. tetrapterus, A. thurberi, A. tibetanus, A. tidestromii, A. tiehmii, A. titanophilus, A. toanus, A. toquimanus, A. tortipes, A. traskiae, A. tricarinatus, A. trichopodus, A. tridactylicus, A. troglodytus, A. tweedyi, A. tyghensis, A. umbellatus, A. umbraticus, A. uncialis, A. utahensis, A. vaccarum, A. vallaris, A. vexilliflexus, A. villosus, A. wardii, A. waterfallii, A. webberi, A. welshii, A. wetherillii, A. whitneyi, A. williamsii, A. wingatanus, A. wittmannii, A. woodruffii, A. wootonii, A. wrightii, A. xiphoides, A. yoderwilliamsii, A. zionis
Subordinate taxa
A. robbinsii var. alpiniformis, A. robbinsii var. fernaldii, A. robbinsii var. harringtonii, A. robbinsii var. jesupii, A. robbinsii var. minor, A. robbinsii var. morganiae, A. robbinsii var. occidentalis, A. robbinsii var. robbinsii
Synonyms Phaca robbinsii
Name authority (Oakes) A. Gray: Manual ed. 2, 98. (1856) unknown
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