Rosy Deer Vetch

Perennial, Herbs, 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, Leaves alternate, Leaves petiolate, Stipules inconspicuous, absent, or caducous, Stipules green, triangulate to lanceolate or foliaceous, Stipules deciduous, Stipules free, Leaves compound, Leaves odd pinnate, Leaf or leaflet margins entire, Leaflets opposite, Leaflets alternate or subopposite, Leaflets 5-9, Leaflets 10-many, Leaves glabrous or nearly so, Flowers solitary in axils, or appearing solitary, Flowers in axillary clusters or few-floweredracemes, 2-6 flowers, Inflorescence umbel-like or subumbellate, Inflorescence axillary, Bracts conspicuously present, Flowers zygomorphic, Calyx 5-lobed, Calyx hairy, Petals separate, Corolla papilionaceous, Petals clawed, Petals white, Petals pinkish to rose, Petals bicolored or with red, purple or yellow streaks or spots, Banner petal ovoid or obovate, Wing petals narrow, oblanceolate to oblong, Wing tips obtuse or rounded, Keel tips obtuse or rounded, not beaked, Stamens 9-10, Stamens or anthers dimorphic, alternating large and small, Stamens diadelphous, 9 united, 1 free, Filaments glabrous, Style terete, Style persistent in fruit, Fruit a legume, Fruit unilocular, Fruit freely dehiscent, Fruit elongate, straight, Fruit or valves persistent on stem, Fruit coriaceous or becoming woody, Fruit exserted from calyx, Fruit internally septate between the seeds, Valves twisting or coiling after dehiscence, Fruit glabrous or glabrate, Fruit 3-10 seeded, Seeds reniform, Seed surface smooth, Seeds olive, brown, or black.

Hosackia rosea, synonym Lotus aboriginus, is a species of legume native to North America. It is known by the common names rosy bird's-foot trefoil and thicket trefoil. It grows in mountains and canyons, often in moist areas. It is a perennial herb lined with leaves each made up of pairs of oval leaflike leaflets 1 to 3 cm long. The inflorescence is a spray of six to 10 white or pink flowers each about 1 cm long. The flower is somewhat tubular, encased at the base in a calyx of sepals and lobed at the mouth. The fruit is a hairless elongated legume pod 3–5 cm long.

It is believed that Hosackia rosea could be a potential host plant for the caterpillars of the critically endangered lotis blue butterfly (syn. Lycaeides idas lotis, Lycaeides argyrognomon lotis, Plebejus anna lotis).