Whited's Milkvetch

Homalobus sinuatus (Piper) Rydb. Bull. Torrey Club 51: 16. 1924.
Astragalus sinuatus Piper, Bull. Torrey Club 28: 40. 1901 . . Phaca sinuata Piper, Contr. U. S. Nat. Herb. 11: 370. 1906.
A perennial; stem decumbent, 3-5 dm. high, terete, villous with short white incurved hairs; leaves 4-5 cm. long; stipules deltoid, 2-3 mm. long; leaflets 1 1-13, elliptic-obovate, truncate or slightly retuse, 10-12 mm. long, shortvillous; peduncles about 6 cm. long; flowers reflexed on short pedicels, probably closely resembling those of 77. Whitedii; pod short-pubescent, arcuate, the stipe about 1 cm. long, the body tapering at each end, 2-2.5 cm. long, 5-6 mm. broad, reticulate, the lower suture curiously sinuate.
Type locality: Eastern Washington. Distribution: Known only from the type locality.

Homalobus whitedii (Piper) Rydb. Bull. Torrey Club 51: 16. 1924.
Astragalus speirocarpus falciformis A. Gray, Bot. Calif. 1: 152. 1876. Not .4. falciformis Desf.
1802. Astragalus speirocarpus curvicarpus Sheldon. Minn. Bot. Stud. 1: 125. 1894. Astragalus Gibbsii falciformis M. E. Jones, Contr. W. Bot. 8: 23. 1898. Astragalus Gibbsii curvicarpus M. E. Jones. Contr. W. Bot. 10: 62. 1902. Astragalus Whitedii Piper, Bull. Torrey Club 29: 224. 1902. Homalobus curvicarpus A. Heller, Muhlenbergia 2: 86. 1905. Astragalus curvicarpus F. Maebr. Contr. Gray Herb. 65: 38. 1922.
A perennial, with a cespitose woody caudex; stems decumbent at the base, 2-4 dm. high, striate, short-pubescent with incurved hairs; leaves 4-7 cm. long; stipules triangular or deltoid, 3 mm. long; leaflets 9-13, obovate or obcordate, 5-15 mm. long, 3-8 mm. wide, short-hairy on both sides, with incurved hairs, obtuse to retuse at the apex; peduncles 5-10 cm. long; racemes 5-8 cm. long, 10-lS-flowered; bracts lanceolate, 2 mm. long, nearly equaling the pedicels; calyx short-pilose, the tube 8 mm. long, gibbous on the upper side, the two upper teeth triangular, the three lower lanceolate, 1 mm. long; corolla ochroleucous; banner 15 mm. long, obovate, with a rather long claw; wings of about the same length, the blades obliquely oblanceolate, with a rounded basal auricle, about as long as the claws; keel-petals about 12 mm. long, the blade nearly semicircular, with a rounded apex and a rounded basal auricle, shorter than the claw; pods short-pubescent, stipitate, the stipe about 1 cm. long, the body strongly curved in a semicircle or more, 2-3 cm. long, 3 mm. wide; seeds obliquely reniform, 3 mm. long, nearly 2 mm. broad.
Type locality: Sierra County, California.
Distribution: Idaho, Oregon, Nevada, and northern California.

Perennial, Herbs, Stems woody below, or from woody crown or caudex, Taproot present, Nodules present, Stems or branches arching, spreading or decumbent, 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, Inflorescences globose heads, capitate or subcapitate, Inflorescence axillary, Bracts very small, absent or caducous, Flowers zygomorphic, Calyx 5-lobed, Calyx glabrous, Petals separate, Corolla papilionaceous, Petals clawed, Petals white, Petals ochroleucous, cream colored, Petals bicolored or with red, purple or yellow streaks or spots, Banner petal narrow or oblanceolate, Wing petals narrow, oblanceolate to oblong, Win g 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 unilocular, Fruit tardily or weakly dehiscent, Fruit oblong or ellipsoidal, Fruit strongly curved, falcate, bent, or lunate, Fruit rugose wrinkled or reticulate, Fruit fleshy, Fruit coriaceous or becoming woody, Fruit exserted from calyx, Fruit inflated or turgid, 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 sinuatus is a species of flowering plant in the legume family known by the common name Whited's milkvetch. It is endemic to Washington in the United States, where it is limited to one creek drainage on the western edge of the Columbia Basin. Its range measures about ten square miles in Chelan and Kittitas Counties in the central part of the state.

This perennial herb has stems up to about 45 centimeters long. In April and May it produces yellowish or cream-colored flowers with purple-tinged keels. The fruit is a legume pod which is so tough it sometimes requires pliers to crack it open. The pod is 2.4 to 2.7 centimeters in length.

This plant grows on harsh, dry, rocky land in the shrubsteppe. Other plants in the habitat may include Lupinus sulphureus, Erigeron linearis, Phlox longifolia, Woodsia oregana, Balsamorhiza sagittata, Lomatium dissectum, Lithophragma bulberifera, and Astragalus purshii. Precipitation amounts to only about 9 inches per year.

There are about 8 populations of the plant, totalling about 5000 individuals. Threats to the species include fire suppression, which has led to a buildup of organic matter that facilitates hotter fires when they do occur now. Other threats include habitat loss, invasive species of plants (such as Bromus tectorum), herbicides, and predation of seed pods by insects.