Astragalus obscurus S. Wats.

Tium obscurum (S. Wats.) Rydberg
Astragalus obscurus S. Wats. Bot. King's Expl. 69. 1871. Tragacantha obscura Kuntze, Rev. Gen. 946. 1891.
A perennial, with a woody root and short cespitose caudex; stems decumbent or ascending, 1—3 dm. long; leaves 5-10 cm. long; stipules deltoid, 3-4 mm. long; leaflets 9-13, oblong to oval or obovate, rounded or retuse at the apex, 5-10 mm. long, 2-4 mm. wide, strigose on both sides; peduncles 5-10 cm. long; racemes 1-5 cm. long; bracts lanceolate, 2 mm. long; pedicels 1 mm. long; calyx strigose, the tube 3-3.5 mm. long, the teeth lanceolate, 1.5 mm. long; corolla white, about 8 mm. long; banner obovate, notched at the apex, rather strongly arcuate at the middle; wings shorter, the blade obliquely lanceolate, falcate, with a large auricle; keel-petals still shorter, the blade broadly lunate, strongly arched at the middle, acutish; pod subsessile, the body linear-oblong, acute at each end, strigose, 2-2.5 cm. long, 3 mm. wide and thick, sulcate on the lower suture, the septum 1.5 mm. wide, nearly meeting the upper suture. .
Type locality: Truckee Pass. Nevada. Distribution: Nevada and eastern 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 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, Leafl ets opposite, Leaflets 5-9, 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 glabrous, Petals separate, Corolla papilionaceous, Petals clawed, Petals white, Petals ochroleucous, cream colored, Petals blue, lavander to purple, or violet, Petals bicolored or with red, purple or yellow streaks or spots, Banner petal narrow or oblanceolate, Wing petals narrow, oblanceolate to oblong, Wing tips obtuse or rounded, Keel petals auriculate, spurred, or gibbous, Stamens 9-10, Stamens diadelphous, 9 united, 1 free, Filaments glabrous, Style terete, Style persistent in fruit, Fruit a legume, Fruit freely dehiscent, Fruit oblong or ellipsoidal, Fruit or valves persistent on stem, 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, bro wn, or black.

Astragalus obscurus is a species of milkvetch known by the common name arcane milkvetch. It is native to the northwestern United States in Idaho and Oregon and northern parts of Nevada and California. It is a plant of rocky areas in mountains and Great Basin plateaus. This is a small, mat-forming perennial herb with tufts of hairy stems approaching a maximum length of 15 centimeters. The leaves are up to 10 centimeters long and made up of thick oval-shaped leaflets. The inflorescence is a dense cluster of 5 to 15 off-white to faintly lilac-tinted flowers, each less than a centimeter long. The fruit is a narrow, leathery legume pod held upright in the infructescence. It may reach 2.5 centimeters in length and usually has two chambers inside.