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Photo is of parent taxon

crescent milkvetch, modest milkvetch

crescent milkvetch

Habit Plants short-lived, sometimes flowering first year, tuft- or loosely mat-forming, subacaulescent to shortly caulescent, 2–35 cm, densely strigose-strigulose, hairs malpighian; from weakly developed caudex.
Stems

usually prostrate or weakly ascending, sometimes erect, 0–20 cm, internodes often concealed by stipules, densely strigose-strigulose.

Leaves

2–13 cm;

stipules sometimes connate-sheathing at proximal nodes, 2–13 mm, submembranous becoming papery;

leaflets (1–)5–21, blades elliptic to obovate or oblanceolate, 3–20 mm, apex obtuse to acute, surfaces strigose.

Racemes

2–13-flowered, flowers ascending;

axis (0.5–)1–6.5 cm in fruit;

bracts 2.5–8 mm;

bracteoles 0–2.

Peduncles

ascending, (1–)2–15(–20) cm.

Pedicels

0.6–2.5 mm.

Flowers

calyx cylindro-campanulate, tube 6.1–9.3 mm, lobes 1.1–2.6 mm;

corolla banner 12.8–16 mm;

keel 11–12.7 mm.

10.3–27(–28) mm;

calyx usually purplish, cylindric, campanulate, or cylindro-campanulate, 6.3–14.2 mm, strigose, tube (3.4–)5.8–13.2 mm, lobes subulate, 1.1–3.7(–4.5) mm;

corolla usually pink-purple, rarely white;

banner recurved through 40°;

keel 8–23.6 mm.

Legumes

16–40 mm, crescentic or incurved through 1/2 their length.

readily deciduous, ascending, green, sometimes mottled, usually incurved, crescentic, mostly dorsiventrally compressed, 15–40 × 5–12 mm, unilocular, distinctly beaked, fleshy becoming stiffly leathery or subligneous, walls much less than 1 mm thick, strigose.

Seeds

44–58.

42–70.

Astragalus amphioxys var. modestus

Astragalus amphioxys

Phenology Flowering Mar–May.
Habitat Dry gravelly hillsides, in blackbrush, four-wing saltbush, Indian ricegrass, needle-and-thread grass, old man sagebrush, mixed grass communities, on sandy silt, limestone, or cindery volcanic debris.
Elevation 1100–1500 m. (3600–4900 ft.)
Distribution
from FNA
AZ; NV; UT; Dry gravelly hillsides; in blackbrush; four-wing saltbush; Indian ricegrass; needle-and-thread grass; old man sagebrush; mixed grass communities; on sandy silt; limestone; or cindery volcanic debris
[BONAP county map]
from USDA
w United States; n Mexico
[WildflowerSearch map]
[BONAP county map]
Discussion

The small-flowered var. modestus forms the other major extreme in flower size within the species, contrasting with the large-flowered var. vespertinus. It is local, forming uniform colonies within the range of var. amphioxys but only from valleys affluent to the Colorado River from San Juan and eastern Kane counties, Utah, and northern Mohave County, Arizona, with disjunct populations in Lincoln County, Nevada. Some plants from northeastern Arizona and northwestern New Mexico have similarly small flowers and might represent an eastward extension of var. modestus; however, in this case introgression from Astragalus missouriensis cannot be ruled out.

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

Varieties 4 (4 in the flora).

Astragalus amphioxys is a widely distributed and complex species consisting of a series of morphological and geographical varieties that are fairly distinctive. The species is common in the middle Colorado Basin and adjoining regions. Astragalus missouriensis, mostly of the Missouri drainage, is a major related species; the ranges of the two are essentially allopatric, but they slightly conjoin in southwestern Colorado and northwestern New Mexico. Flowering material is difficult to identify in the Four Corners area of the Southwest.

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

Key
1. Calyx tubes (5.8–)7–13.2 mm; banners (16.2–)19–27(–28) mm; keel (13.2–)14.3–23.6 mm; Arizona, Colorado, Nevada, New Mexico, Texas, Utah.
→ 2
2. Calyx tubes (5.8–)7–10.5 mm; banners (16.2–)19–24.5 mm; keel (13.2–)14.3–18.8(–19.6) mm; Arizona, Colorado, Nevada, New Mexico, Texas, Utah.
var. amphioxys
2. Calyx tubes 8.8–13.2 mm; banners 23–27(–28) mm; keel 19–23.6 mm; extreme n Arizona, sw Colorado, nw New Mexico, se Utah.
var. vespertinus
1. Calyx tubes 3.4–9.3 mm; banners 10.3–16 mm; keel 8–12.7 mm; Mohave and Coconino counties, Arizona, se Nevada, sc Utah.
→ 3
3. Calyces cylindro-campanulate, tubes 6.1–9.3 mm; keel 11–12.7 mm; seeds 44–58; nc, nw Arizona, Lincoln County, Nevada, and Kane County, Utah.
var. modestus
3. Calyces campanulate, tubes 3.4–4.8 mm; keel 8–11.5 mm; seeds 26–36; Mohave County, Arizona, Clark County, Nevada.
var. musimonum
Source FNA vol. 11. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae > Astragalus > sect. Argophylli > Astragalus amphioxys Fabaceae > subfam. Faboideae > Astragalus > sect. Argophylli
Sibling taxa
A. amphioxys var. amphioxys, A. amphioxys var. musimonum, A. amphioxys var. vespertinus
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. 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. 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. amphioxys var. amphioxys, A. amphioxys var. modestus, A. amphioxys var. musimonum, A. amphioxys var. vespertinus
Name authority Barneby: Leafl. W. Bot. 9: 89. (1960) A. Gray: Proc. Amer. Acad. Arts 13: 366. (1878)
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