Humboldt River Milkvetch

Xylophacos iodanthus (S. Wats.) Rydb. Bull. Torrey Club 52: 144. 1925.
Astragalus iodanthus S. Wats. Bot. King's Expl. 70. 1871. Tragacanlha iodantha Kuntze, Rev. Gen. 945. 1891.
A perennial, with a cespitose woody caudex; stems decumbent, flexuose, 2-6 dm. long, glabrate or sparingly strigose; stipules triangular, 2-4 mm. long, hyaline, reflexed; leaves spreading, 4-10 cm. long; leaflets 17-21, obovate or oval, 8-12 mm. long, 4—6 mm. wide, glabrous or ciliolate on the margins and ribs, obtuse, rounded, or retuse at the apex; peduncles 3-5 cm. long; racemes short and rather dense; bracts lanceolate, 3 mm. long, longer than the pedicels; calyx sparingly strigose with black hairs, the tube about 5 mm. long, the teeth subulate, 2 mm. long; corolla light-purple or white, 12-15 mm. long; banner oblong, abruptly bent at the middle, deeply notched at the apex; wings shorter, the blades obliquely oblaneeolate, with a rounded basal auricle; keel-petals much shorter, broader, strongly arcuate, and rounded at the apex; pod lanceolate in outline, strongly arcuate, about 3 cm. long and 8 mm. wide, mottled, sparingly strigose, finely cross-reticulate, acute at each end, usually depressed, and somewhat sulcate on the sutures.
Type locality: Virginia City. Nevada. Distribution: Nevada and eastern California.

Perennia l, Herbs, Stems woody below, or from woody crown or caudex, Taproot present, Nodules present, Stems or branches arching, spreading or decumbent, Stems prostrate, trailing, or mat forming, Stems less than 1 m tall, Stems solid, Stems or young twigs glabrous or sparsely glabrate, 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 umbel-like or subumbellate, Inflorescence axillary, Bracts very small, absent or caducous, Flowers zygomorphic, Calyx 5-lobed, Calyx glabrous, Petals separate, Corolla papilionaceous, Petals clawed, Petals pinkish to rose, Petals blue, lavander to purple, or violet, Banner petal narrow or oblanceolate, Wing petals narrow, oblanceolate to oblong, W ing 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 humistrate, lying on the ground, Fruit tardily or weakly dehiscent, Fruit oblong or ellipsoidal, Fruit strongly curved, falcate, bent, or lunate, Fruit spirally coiled or contorted, Fruit coriaceous or becoming woody, Fruit exserted from calyx, 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 lentiginosus var. iodanthus, synonym Astragalus iodanthus, is a variety of Astragalus lentiginosus, a flowering plant in the legume family, Fabaceae. It is known by the common names Humboldt River milkvetch and violet milkvetch. It is native to the western United States, where its range includes California, Idaho, Nevada, Oregon, and Utah. It grows on hills and in valleys in barren sandy and volcanic soils in habitat such as sagebrush.

This perennial herb produces several prostrate stems up to 40 centimeters long. The compound leaves are made up of 9 to 21 rounded or teardrop-shaped leaflets each up to 1.8 centimeters long. The inflorescence is a raceme of flowers in shades of reddish purple or white to cream with a purple tip on the keel petal. There are up to 25 flowers in a raceme, and they are crowded when first blooming but spread out over time. The fruit is a legume pod up to 4 centimeters long, becoming dark, mottled, and papery to leathery with age.