Smithsonian Contr. Knowl. 5(6): 31. 1853.
Herbs (2–)3–6(–7) dm. Stems branched distally, hairs incurved. Leaves: petiole 1–2.5 mm; blade mostly lanceolate or narrowly ovate to elliptic, sometimes obovate proximally, 15–60 × 2–10 mm, base cuneate, apex usually acute to attenuate-acuminate, sometimes obtuse proximally. Racemes 2–20(–30) × 0.3–0.6 cm; peduncle to 6 cm; bracts narrowly lanceolate or ovate-subulate. Pedicels 0.4–0.5 mm, pubescent. Cleistogamous flowers usually present on much-reduced axillary branches, chasmogamous flowers sometimes absent, 1.5–2.1 mm. Flowers: non-wing sepals ovate to lanceolate, 1.2–1.8 mm; wings obovate, 1–2 mm wide; keel 1.5–3 mm. Fruits ovoid, subglobose, or subobovoid, 3–5 × 2.8–4 mm. Seeds 2–3 mm.
Phenology: Flowering (mid–)late summer–fall.
Habitat: Igneous, limestone, gravelly, sandy, or silty loam soils, in dry to moist, open to shaded grasslands, shrublands, woodlands, disturbed areas.
Elevation: 1200–2600 m.
Ariz., N.Mex., Mexico (Chihuahua, Colima, Durango, Guanajuato, Jalisco, Michoacán, Nayarit, Sinaloa, Sonora, Zacatecas), South America.
Monnina wrightii is amphitropically disjunct in Argentina and Bolivia, with single collections each from Peru and Uruguay.