Duration: Perennial

Nativity: Native

Lifeform: Subshrub

General: Perennial with several to many stems that branch from base, ascending to erect, 30-70 cm, commonly woody at base, pale green, glabrous or soon glabrate with internodes much longer than the leaves.

Leaves: On petioles 1-5 mm long, pinnate with 3-5 leaflets, oblong-linear to oblong-oblanceolate to obovate, 1.2-5 mm wide, 5-15 mm long, finely strigose or eventually glabrate, green.

Flowers: On peduncles 3-12 cm long, 1-3 flowered, stipules reduced to glands, bearing a small leafy bract 3-6 mm long, just below the flowers, or bractless; pedicels appressed-pubescent, 1-3 mm long; calyx strigose, 7-9 mm long, cylindro-campanulate; corolla 15-25 mm long, yellow or cream, suffused with red, teeth 2-4 mm long, shorter than calyx tube.

Fruits: Pods narrowly oblong, 32-45 mm long, 3.7-4.2 mm wide, straight, glabrous.

Ecology: Found on sandy, gravelly, or clayey soils often along washes and on rocky hillsides below 5,500 ft (1676 m); flowers February-May.

Distribution: s UT, NV, AZ, se CA; south to Baja Calif., MEX

Notes: This is the most xerophytic of the Lotus in Arizona, forming rounded clumps with brittle stems; like other species in this genera it is known to hybridize.

Ethnobotany: Unknown, but other species in the genera have uses.

Etymology: Acmispon comes from the Greek acme for point or hook, while rigidus means rigid.

Synonyms: Lotus rigidus, Hosackia rigida

Editor: SBuckley, 2010

Plant: Perennial, shrub-like, finely strigose; stems ascending, clustered, branched, 0.5-1.5 m

Leaves: irregularly pinnate to ± palmate, well spaced; stipules gland-like or 0; leaflets 3-4, 0.5-1.5 cm, oblanceolate to obovate; axis (including petiole) 1-8 mm

INFLORESCENCE: 1-3-flowered; peduncle 3-6 cm; bract near top or 0

Flowers: calyx 5-8 mm, lobes < tube; corolla 12-22 mm, wings > keel; stamens 10, 9 filaments fused, 1 free; stigma ± glabrous

Fruit: legume, slowly dehiscent, spreading or erect, 2-4 cm, oblong, ± straight, much exserted, generally glabrous; Seeds several-many, often ± reniform, generally hard, smooth

Misc: Chaparral, desert flats, washes, foothills; < 1550 m.; Mar-May

References: Jepson Manual 1993