Psorothamnus scoparius
N. Amer. Fl. 24: 48. 1919.
Shrubs or subshrubs. Branches broomlike; sterile shoots not sharp-tipped. Stems to 10 dm, gland-dotted when young, often gray-strigulose, hairs antrorse. Leaves unifoliolate or pinnate, (0.2–)0.4–2 cm; leaflets 1 or 3, blades linear-oblanceolate, 2–15 mm, terminal leaflet longer than laterals, surfaces gland-dotted abaxially, strigulose. Racemes relatively loose; rachis not spine-tipped in anthesis, (0.1–)0.3–1.8 cm; bracts ovate to oblanceolate, 1.5–2.5 mm; bracteoles absent. Flowers: calyx 3.5–4.5 mm, densely pilosulous, tube 2.2–3 mm, ribs fairly prominent, intervals each with 1 row of (1 or)2–5 glands, lobes ovate, abaxial lobe shorter; corolla usually bright blue or blue-purple with pale yellow eye, rarely white; banner 6.4–9 mm, oblong-obovate, base cordate; wings oblong-lanceolate, 5–6.7 × 1.7–2.1 mm; keel obliquely obovate, (4.2–)4.6–5.8 × 1.7–2.1 mm; stamens 5.5–8.5 mm; filaments distinct to 2.3–2.6 mm; anthers 0.6–0.9 mm, connective gland-tipped. Legumes obliquely obovate, 4 mm, with large glands distally, glabrous proximally, pilosulous distally. Seeds 2.1–2.7 mm. 2n = 20.
Phenology: Flowering fall (late spring–early summer).
Habitat: Sandy desert flats or dunes.
Elevation: 1100–1600 m.
Distribution
Ariz., N.Mex., Tex., Mexico (Chihuahua, Coahuila).
Discussion
Psorothamnus scoparius, a distinctive broomlike plant, is usually nearly leafless by flowering time. In Texas, P. scoparius is known only from El Paso and Hudspeth counties in the trans-Pecos region.
Selected References
None.