Shrubs. Branches irregular, stiff; sterile shoots often sharp-tipped. Stems 3–10 dm, gland-dotted distally when young, glands prickle-shaped, hairy to glabrate. Leaves usually pinnate, sometimes unifoliolate distally, (0.3–)1–3.5(–5.5) cm; leaflets (1 or 3)5–11, blades ovate, obovate, lanceolate, linear, elliptic, rhombic-elliptic, rhombic-ovate, or linear-oblanceolate, 2–14(–17) mm, terminal leaflet seldom longer than laterals, surfaces gland-dotted abaxially, silky-strigulose, villous-tomentulose to glabrate, loosely hairy, or glabrous. Racemes loose; rachis without thornlike tip in anthesis, (1–)1.5–12 cm; bracts subulate to linear, 2.5–4 mm; bracteoles present. Flowers: calyx 5–9 mm, pilosulous to minutely puberulent, strigulose, silky-canescent, or glabrate, tube 3–4.5 mm, ribs prominent, broader adaxial intervals with 2 rows, narrower one with 1 row of 3–5 glands, lobes broadly lanceolate, triangular, or lanceolate, abaxial lobe often shorter; corolla indigo-blue to violet; banner flabellate to flabellate-ovate, 6.3–10 mm, base cuneate to auriculate, claw cuneate; wings oblong to oblong-ovate, 5.4–8.2 × 2.2–3.5 mm; keel obliquely obovate, 5.8–8.4 × 3.3–4.9 mm; stamens (5.5–)6.5–9.8 mm; filaments distinct to (3–)3.5–5.6 mm; anthers (0.8–)0.9–1.3 mm, connective not gland-tipped. Legumes ovoid-ellipsoid or obliquely ellipsoid, 8–10 mm, with scattered blister-glands, glands not confluent, glabrous or sparsely villosulous. Seeds (4.7–)5–6 mm.

Distribution

sw United States, nw Mexico.

Discussion

Varieties 4 (4 in the flora).

Selected References

None.

Lower Taxa

Psorothamnus arborescens var. arborescens, Psorothamnus arborescens var. californicus, Psorothamnus arborescens var. minutifolius, Psorothamnus arborescens var. pubescens

Key

1	Calyces 7–9 mm, lobes to 3–5.4 mm.	> 2
2	Leaflets (3 or)5 or 7, blades ovate to obovate, elliptic, or broadly lanceolate.	Psorothamnus arborescens var. arborescens
2	Leaflets (5 or)7–11, blades linear to linear-oblanceolate.	Psorothamnus arborescens var. pubescens
1	Calyces 5–6.9 mm, lobes to 1.8–3.7 mm.	> 3
3	Calyx tube glabrate or puberulent; leaflet blades lanceolate to rhombic-ovate or -elliptic, surfaces loosely hairy or glabrous.	Psorothamnus arborescens var. minutifolius
3	Calyx tube silky-canescent externally; leaflet blades linear-oblanceolate to narrowly elliptic, surfaces silky-strigulose.	Psorothamnus arborescens var. californicus