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Cusick's milk-vetch

ashen milkvetch, silverline locoweed

Habit Plants clump-forming, slender, 30–70 cm, strigulose; from subterranean or superficial caudex. Plants loosely or densely tuft-forming, acaulescent or shortly caulescent, 10–48 cm, strigulose, pilosulous, or villosulous, hairs basifixed; from branched caudex, branches often with conspicuous thatch of marcescent leaf rachises.
Stems

erect to ascending, strigulose.

prostrate, 0–15(–25) cm, internodes to 2(–2.5) cm, strigulose, pilosulous, or villosulous.

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.

4–24 cm;

stipules sometimes obscurely connate at proximal nodes, 2–15 mm, submembranous becoming papery-scarious;

leaflets 11–27(–31), blades oblanceolate, obovate, obovate-cuneate, rhombic, rhombic-ovate, or rhombic-elliptic, rarely suborbiculate, 2–27 mm, apex usually obtuse or acute, rarely emarginate, surfaces usually pubescent, sometimes glabrescent or glabrous adaxially.

Racemes

becoming loosely (3–)4–14(–18)-flowered;

axis 1–8.5 cm in fruit;

bracts 0.8–1.5 mm;

bracteoles 0.

loosely (9 or)10–25(–35)-flowered, flowers ascending;

axis (1.5–)2–20 cm in fruit;

bracts 1.5–11 mm;

bracteoles usually 0(–2).

Peduncles

erect or incurved-ascending, 5–15(–22) cm.

incurved-ascending or erect, 4–40 cm.

Pedicels

ascending, 1.2–3.5 mm.

0.6–3.4 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.

11.8–24 mm;

calyx cylindric to deeply campanulate, (5–)6.4–14 mm, loosely strigulose, pilosulous, or villous, tube (3.5–)4.5–10.2 mm, lobes subulate or triangular-subulate, 1.2–3.8 mm;

corolla usually pink-purple to dull lilac, rarely white or nearly so;

banner recurved through 45°;

keel 10.2–20.1 mm.

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.

ascending, green or purplish becoming stramineous or brownish, lunately incurved or straight proximally and only beak incurved, obliquely ovoid-acuminate, lanceoloid-, oblong-, or ovoid-ellipsoid, strongly obcompressed, 13–34 × 5–10(–12) mm, ± unilocular, valves less than 1 mm thick, thinly to thickly fleshy becoming thinly leathery, stiffly leathery, or subligneous, usually densely to sparsely strigulose or pilosulous, rarely glabrous.

Seeds

10–20.

24–36.

Astragalus cusickii

Astragalus tephrodes

Distribution
from USDA
nw United States
[WildflowerSearch map]
[BONAP county map]
from USDA
sw United States; nw Mexico
[WildflowerSearch map]
[BONAP county map]
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.

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

Varieties 3 (3 in the flora).

Astragalus tephrodes consists of two intergrading varieties (var. brachylobus, var. tephrodes) that are rather widely distributed and one (var. chloridae) that is narrowly distributed. R. C. Barneby (1947b, 1964) discussed the taxonomic complexity of the species and described the clinal variation from Arizona to the western limits of the species distribution, resulting in a classification that is necessarily arbitrary.

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

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.
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.
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.
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.
var. packardiae
1. Calyx tubes (3.5–)4.5–6.8(–8) mm, lobes 1.2–2.2 mm; corolla banners 11.8–17.5 mm, keel 10.2–14.5 mm; legumes 13–20 mm, thinly leathery; leaflets mostly conduplicate; sw New Mexico and adjoining Mexico, westward across Arizona to Verde Valley, Yavapai County.
var. tephrodes
1. Calyx tubes 7.1–10.2 mm, lobes 1.7–3.8 mm; corolla banners (14–)16.8–24 mm, keel 14.7–20.1 mm; legumes 17–34 mm, stiffly leathery or subligneous; leaflets mostly flat; Arizona, Nevada, California, and w New Mexico.
→ 2
2. Peduncles (4–)5–15(–21) cm; raceme rachis (1.5–)2–8(–11) cm in fruit; broadly distributed from se California and Nevada to New Mexico.
var. brachylobus
2. Peduncles 13–40 cm; raceme rachis (4–)7–20 cm in fruit; nw Arizona, extreme s Nevada.
var. chloridae
Source FNA vol. 11. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae > Astragalus > sect. Cusickiani Fabaceae > subfam. Faboideae > Astragalus > sect. Argophylli
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. 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. 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
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. 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. 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. cusickii var. cusickii, A. cusickii var. flexilipes, A. cusickii var. packardiae, A. cusickii var. sterilis
A. tephrodes var. brachylobus, A. tephrodes var. chloridae, A. tephrodes var. tephrodes
Name authority A. Gray: Proc. Amer. Acad. Arts 13: 370. (1878) A. Gray: Smithsonian Contr. Knowl. 5(6): 45. (1853)
Web links