Triplerib Milkvetch

Hamosa tricarinata (A. Gray) Rydb. Bull. Torrey Club 54:20. 1927.'
Astragalus tricarinatus A. Gray, Proc. Am. Acad. 12: 56. 1876.
A perennial, from a woody base; stems erect, 3-5 dm. high, stout, strigose; leaves 10-15 cm. long, ascending; stipules ovate, 2 mm. long; leaflets 25-35, oval, 7-15 mm. long, rounded or retuse at the apex, silvery above, strigose beneath with short lanceolate hairs; peduncles 1-2 dm. long; racemes lax, 5-10 cm. long; bracts lanceolate, 2 mm. long; calyx black-hairy, the tube 4 mm. long and nearly as broad, the teeth lance-subulate, 2 mm. long; corolla white; banner broadly obovate, abruptly arcuate, about 15 mm. long; wings 12 mm. long, the blade lanceolate, falcate, with a large reflexed auricle; keel-petals 10 mm. long, the blade broadly lunate, strongly arched, obtuse; pod glabrous, slightly arcuate, 3-3.5 cm. long, 4—5 mm. wide and 4 mm. thick, broadly sulcate on the lower suture, deeply cordate in cross-section.
Type locality: White Water, San Bernardino County, California. Distribution: San Bernardino County, California.

Perennial, Herbs, Stems woody below, or from woody crown or caudex, Taproot present, Nodules present, Stems erect or ascending, Stems less than 1 m tall, Stems solid, Stems or young twigs sparsely to densely hairy, 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 white, 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 stipitate, Fruit tardily or weakly dehiscent, Fruit oblong or ellipsoidal, Fruit exserted from calyx, Fruit beaked, Fruit glabrous or glabrate, Fruit 11-many seeded, Seeds cordiform, mit-shaped, notched at one end, Seed surface smooth, Seeds olive, brown, or black.

Astragalus tricarinatus is a rare species of milkvetch known by the common name triplerib milkvetch, or triple-ribbed milkvetch.

It is endemic to California, where it can be found in the region where the San Bernardino Mountains meet the Mojave Desert and the Colorado Desert. It grows in desert scrub and expanses of rock litter amongst stands of Joshua trees. The plant is known from only one location and there were twenty individuals remaining there in 1998, when it was federally listed as an endangered species.