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Pursh's milkvetch, woollypod milkvetch

Tygh Valley milkvetch

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

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

several or numerous, prostrate or decumbent to ascending, forming loose mats, 10–55 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.

5–14 cm;

leaflets (7)15–21; oval-obovate to elliptic, 6–17 × 2–7 mm;

tips obtuse to subacute;

surfaces densely villous-tomentose;

stipules 3–6 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; dense, closely crowded; ovoid to oblong; later elongating and becoming cylindrical; (10)20–40-flowered;

peduncles 5–12 cm;

bracts 2–5 mm;

pedicels 0.5–1 mm;

bracteoles 0.

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).

spreading to ascending at anthesis;

calyces 6.6–7.8 mm, densely white; silky villous-tomentose;

tubes 3.9–4.5 mm;

teeth narrowly subulate, 2.7–3.5 mm;

corollas 9–12 mm, pale yellow, pubescent, marcescent;

ovules 6–8.

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.

bilocular, mostly enclosed by persistent calyces, spreading to somewhat declined, obliquely ovoid; straight, obscurely trigonous, 4.5–6 × 3 mm, canescently tomentulose;

valves stiffly papery;

body contracted basally into stipe-like necks, 0.4–0.6 mm.

Astragalus purshii

Astragalus tyghensis

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.

Dry hillsides and valleys, open pine woodlands, sagebrush communities. Flowering May–Jun. 300–1000 m. Col. Native. Endemic to Oregon.

The pubescent petals of this narrow endemic species distinguish it from all other Oregon milkvetches.

Source Flora of Oregon, volume 2, page 671
Richard Halse
Flora of Oregon, volume 2, page 676
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. tetrapterus, A. toanus, A. tweedyi, 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 spaldingii var. tyghensis
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