Mearns' Bird's Foot Trefoil

Perennial, Herbs, Stems woody below, or from woody crown or caudex, Plants with rhizomes or suckers, Taproot present, Nodules present, Stems prostrate, trailing, or mat forming, Stems less than 1 m tall, Stems solid, Stems or young twigs sparsely to densely hairy, Stem hairs hispid to villous, Stems silvery, canescent, tomentose, cobwebby, or wooly, Leaves alternate, Leaves petiolate, Stipules inconspicuous, absent, or caducous, Stipules persistent, Stipules free, Stipules reduced to glands, Leaves compound, Leaves palmately 2-3 foliate, Leaves palmately 5-11 foliate, Leaves odd pinnate, Leaf or leaflet margins entire, Leaflets opposite, Leaflets alternate or subopposite, Leaflets 3, Leaflets 5-9, Leaves glabrous or nearly so, Flowers in axillary clusters or f ew-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 orange or yellow, 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 2-seeded, Fruit 3-10 seeded, Seeds renifo rm, Seed surface smooth, Seeds olive, brown, or black.

Acmispon mearnsii, synonym Lotus mearnsii, is a species of flowering plant in the legume family endemic to Arizona in the United States. It known by the common name Mearns' bird's-foot trefoil. In Arizona, it occurs in Coconino, Navajo, and Yavapai Counties.