Psorothamnus spinosus
Mem. New York Bot. Gard. 27: 25. 1977.
Trees, small, rounded, appearing shrublike when young. Branches divergent; sterile shoots sharp-tipped or thornlike. Stems 70(–100) dm, gland-dotted distally when young, glands orange, silvery-silky to glabrate. Leaves unifoliolate, 0.2–2.2 cm, leaflet 1, blade oblanceolate or cuneate-oblanceolate, surfaces gland-tipped abaxially, strigulose. Racemes loose; rachis with thornlike tip in anthesis, 1–4 cm; bracts ovate, 0.5–8 mm; bracteoles present. Flowers: calyx 4.5–5.2 mm, silky-strigulose, tube 3–3.8 mm, ribs not prominent, intervals each with (0 or)1(or 2) large glands, lobes ovate, abaxial lobe shorter; corolla indigo-blue; banner obcordate, 6.4–7.5 mm, base auriculate, claw linear to cuneate; wings broadly oblanceolate, 5.5–6.8 × (2.4–)3–4.5 mm; keel obovate, 6.6–8.2 × 4.2–5.4 mm; stamens 9.5–11.5 mm; filaments distinct to 4.1–4.9 mm; anthers 0.7–1.1 mm, connective gland-tipped. Legumes obovoid, 3–4 mm, with several glands proximally, pilosulous distally. Seeds rarely 2, 3 mm.
Phenology: Flowering late spring–mid summer (fall).
Habitat: Rocky or sandy deserts, wetter areas.
Elevation: -70–400 m.
Distribution
Ariz., Calif., Nev., Mexico (Baja California, Sonora).
Discussion
Leaves of Psorothamnus spinosus are not retained for long; most of the time, the tree crown consists of a rounded mass of silvery branches. In California, P. spinosus is known from the desert areas in the southeastern part of the state.
Selected References
None.