Descanso Milkvetch

Phaca oocarpa (A. Gray) Rydberg
Astragalus Crotalariae Torr. Bot. Mex. Bound. Surv. 56. 1859. Not Phaca Crotalariae Benth.
1848. Astragalus crotalar hides Torr. Bot. Mex. Bound. Surv. pi. 17, hyponym. 1859. Astragalus oocarpus A. Gray, Proc. Am. Acad. 6: 213. 1864. Tragacanlha oocarpa Kuntze, Rev. Gen. 946. 1891.
Perennial; stem 1-2 m. high, sulcate and angled, glabrous or nearly so, sometimes tinged with purple, branched; leaves ascending, 8-15 cm. long; stipules deltoid, 3-4 mm. long; leaflets 15-21, oval, rather thick, 1-2 cm. long, 5-10 mm. wide, glabrous or nearly so, rounded or retuse at the apex; peduncles 5-7 cm. long; racemes lax, 9-12 cm. long; bracts lanceolate, 1-2 mm. long; flowers ascending, with very short pedicels; calyx-tube 4 mm. long, finely pubescent, the lobes triangular, 1 mm. long; corolla ochroleucous; banner obovate, 10-12 mm. long; wings decidedly shorter, the blade oblong-lunate, with a reflexed basal auricle, obtuse, fully as long as the claw; keel-petals broader, more curved; pod erect, glabrous, rather firm, ovoid, shortacute at the base, more tapering at the apex, 2.5 cm. long, fully 1 cm. wide; seeds obliquely reniform.
Type locality: Mountains east of San Diego, California.
Distribution: San Diego County. California.

Perennial, Herbs, Stems woody below, or from woody crown or caudex, Taproot present, Nodules present, Stems erect or ascending, Stems or branches arching, spreading or decumbent, Stems less than 1 m tall, Stems 1-2 m tall, Stems solid, Stems or young twigs glabrous or sparsely glabrate, Leaves alternate, Leaves petiolate, Stipules conspicuous, Stipules membranous or chartaceous, Stipules persistent, Stipules free, Leaves compound, Leaves odd pinnate, Leaf or leaflet margins entire, Leaflets opposite, Leaflets 10-many, Leaves hairy on one or both surfaces, Inflorescences racemes, Inflorescence axillary, Bracts very small, absent or caducous, Flowers zygomorphic, Calyx 5-lobed, Calyx hairy, Petals separate, Corolla papilionaceous, Petals clawed, Petals ochroleucous, cream colored, Banner petal narrow or oblanceolate, Wing petals narrow, oblanceolate to oblong, Wing tips obtuse or rounded, Keel petals auriculate, spurred, or gibbous, Keel tips obtuse or rounded, not beaked, Stamens 9-10, Stamens diadelphous, 9 united, 1 free, Filaments glabrous, Style terete, Style persistent in fruit, Fruit a legume, Fruit unilocular, Fruit freely dehiscent, Fruit oblong or ellipsoidal, Fruit or valves persistent on stem, Fruit coriaceous or becoming woody, Fruit exserted from calyx, Fruit inflated or turgid, Fruit beaked, Fruit glabrous or glabrate, Fruit hairy, Fruit 11-many seeded, Seeds cordiform, mit-shaped, notched at one end, Seed surface smooth, Seeds olive, brown, or black.

Astragalus oocarpus is a rare species of milkvetch known by the common names San Diego milkvetch and Descanso milkvetch.

It is endemic to southern California, where it is known only from the Peninsular Ranges of San Diego County. Its range may extend north into Riverside County. It is a plant of the chaparral slopes and woodlands of the mountains.