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Pursh's milkvetch, woollypod milkvetch

four-wing milkvetch

Habit Plants perennial, acaulescent to shortly caulescent, densely villous to villous-tomentose, hairs basifixed. Plants perennial, caulescent, strigillose, hairs basifixed.
Stems

prostrate, loosely to densely tufted, 0–20 cm.

several, ascending to erect, becoming decumbent in fruit, 10–35(45) cm.

Leaves

1–12(17) cm;

leaflets (3)5–17(21), elliptic to oblanceolate, 2–14(20) × 1–7 mm;

tips obtuse to acute;

surfaces densely villous;

stipules 2.5–15 mm; free.

1.5–9 cm;

leaflets 9–23, linear, narrowly oblong or elliptic, 1–33 × 0.3–3.2 mm;

tips obtuse to acute;

surfaces glabrous to strigose;

terminal leaflets confluent with rachis in the uppermost leaves;

stipules 2–5.5 mm; free.

Inflorescences

racemes or subumbels, 1–12-flowered;

peduncles 1–14 cm;

bracts 4–9 mm;

pedicels 2–4.3 mm;

bracteoles 0–2.

racemes 6–15-flowered;

peduncles 1–6.5 cm;

bracts 1.5–3.5 mm;

pedicels 1.4–4.3 mm;

bracteoles 0–2.

Flowers

ascending at anthesis;

calyces 5.5–16(19) mm, often purple, villous-pilose with white or mixed white and black hairs;

tubes 8.5–12.5 mm;

teeth subulate, 2.2–6 mm;

corollas 19–27 mm; whitish to ochroleucous or pink-purple;

ovules 14–40(46).

ascending at anthesis;

calyces (4)5.5–8.7 mm, strigose with black or mixture of black and white hairs;

tubes 3.5–7 mm;

teeth subulate or triangular, 0.5–2.8 mm;

corollas 15–19 mm, white to yellowish and pink or bright pink-purple-tinged;

keel faintly to darkly purple-tipped;

ovules 28–42.

Fruits

unilocular, ascending, obliquely ovoid, usually curved, obcompressed, scarcely to deeply sulcate; (7)13–27(30) × 3.5–11 mm, densely white to tawny tomentose or densely villous;

hairs nearly always concealing valve surfaces;

valves coriaceous, sessile or on gynophores 0–1.6 mm.

unilocular, declined or pendulous, obliquely oblong or clavate-oblong, curved or coiled, strongly carinate, obcompressed early, becoming sharply tetragonal and 4-winged;

wings up to 2.5 mm wide at maturity; (16)20–40 × (4)6–10 mm, glabrous to strigose;

valves stiffly papery to subcoriaceous;

stipes 0.

2n

=22.

Astragalus purshii

Astragalus tetrapterus

Distribution
[WildflowerSearch map]
[BONAP county map]
[WildflowerSearch map]
[BONAP county map]
Discussion

Western North America. ~8 varieties; 4 varieties treated in Flora.

Throughout western North America, particularly in the Intermountain Region, this is a low, tufted milkvetch with white or gray villous hairs and pods resembling balls of cotton. Barneby (1964) stated, “Attempts to devise a practical key to the varieties of A. purshii are never wholly successful.” Variety ophiogenes, the Snake River milkvetch, a native of Idaho, has been reported from Malheur County, but this is apparently based on misidentifications of A. purshii var. lagopinus. Variety ophiogenes has 3–11-flowered racemes and 9–17 leaflets.

Hillsides of ash-clay-tuff, sandy soils, sagebrush. Flowering May–Jun. 900–1700 m. BR, ECas, Owy. ID, NV; southeast to AZ. Native.

The four-winged fruits of this species are unique among Oregon milkvetches.

Source Flora of Oregon, volume 2, page 671
Richard Halse
Flora of Oregon, volume 2, page 675
Richard Halse
Sibling taxa
A. accidens, A. agrestis, A. alpinus, A. alvordensis, A. applegatei, A. arthuri, A. atratus, A. australis, A. beckwithii, A. californicus, A. calycosus, A. canadensis, A. caricinus, A. collinus, A. conjunctus, A. curvicarpus, A. cusickii, A. diaphanus, A. drummondii, A. eremiticus, A. filipes, A. gambellianus, A. geyeri, A. hoodianus, A. howellii, A. inflexus, A. iodanthus, A. kentrophyta, A. lemmonii, A. lentiginosus, A. malacus, A. misellus, A. mulfordiae, A. multiflorus, A. newberryi, A. nudisiliquus, A. obscurus, A. peckii, A. platytropis, A. reventus, A. robbinsii, A. salmonis, A. sclerocarpus, A. sheldonii, A. solitarius, A. spaldingii, A. sterilis, A. succumbens, A. tegetarioides, A. tetrapterus, A. toanus, A. tweedyi, A. tyghensis, A. umbraticus, A. vallaris, A. whitneyi
A. accidens, A. agrestis, A. alpinus, A. alvordensis, A. applegatei, A. arthuri, A. atratus, A. australis, A. beckwithii, A. californicus, A. calycosus, A. canadensis, A. caricinus, A. collinus, A. conjunctus, A. curvicarpus, A. cusickii, A. diaphanus, A. drummondii, A. eremiticus, A. filipes, A. gambellianus, A. geyeri, A. hoodianus, A. howellii, A. inflexus, A. iodanthus, A. kentrophyta, A. lemmonii, A. lentiginosus, A. malacus, A. misellus, A. mulfordiae, A. multiflorus, A. newberryi, A. nudisiliquus, A. obscurus, A. peckii, A. platytropis, A. purshii, A. reventus, A. robbinsii, A. salmonis, A. sclerocarpus, A. sheldonii, A. solitarius, A. spaldingii, A. sterilis, A. succumbens, A. tegetarioides, A. toanus, A. tweedyi, A. tyghensis, A. umbraticus, A. vallaris, A. whitneyi
Subordinate taxa
A. purshii var. glareosus, A. purshii var. lagopinus, A. purshii var. purshii, A. purshii var. tinctus
Synonyms Astragalus purshii var. ophiogenes Astragalus cinerascens, Astragalus tetrapterus var. cinerascens, Astragalus tetrapterus var. tetrapterus
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