Shrubs. Branches irregular; ste­rile shoots not or faintly sharp-tipped. Stems 3–10 dm, ± eg­landular when young, strigulose. Leaves pinnate, 1–4 cm; leaf­lets 3–7(or 9), blades obovate to linear-elliptic, linear-oblanceolate, or linear, (2–)3–25 mm, ter­minal leaflet seldom longer than laterals, surfaces gland-dotted abaxially, strigulose, more strongly so adaxially. Racemes loose; rachis without thornlike tip in anthesis, 2–9(–11) cm; bracts subulate, 1.2–2 mm; bracteoles present. Flowers: calyx (5–)5.4–7.7 mm, glabrous or strigulose externally, tube (5–)5.4–7.7 mm, ribs prominent, intervals each with 1 row of 2–5 glands, adaxial ones with 4–7 scattered glands, lobes lanceolate or triangular-lanceolate, abaxial lobe becoming reflexed, nearly equal but narrower; corolla magenta-purple; banner flabellate to flabellate-ovate, 7.3–9.3 mm, base cuneate or auriculate, claw cuneate; wings oblong to oblong-ovate, 6.1–7.3 × (2.6–)2.8–3.8 mm; keel obliquely obovate, (6–)6.4–7.5 × (3.6–)4–4.7 mm; stamens 6.6–9.1 mm; filaments distinct to 3.2–4.4 mm; anthers (0.7–)0.9–1.2 mm, connective not gland-tipped. Legumes obliquely obovoid, 7–10 mm, with numerous blister-glands, glands confluent into vertical ridges, glabrous or glabrate. Seeds 4.4–5.8 mm.

Distribution

sw United States.

Discussion

Varieties 2 (2 in the flora).

Psorothamnus fremontii is often separated from P. arborescens with difficulty because the critical distinction requires mature fruit. Most other features are too variable or overlapping to be of much use. Flowering specimens can usually be identified if the location of the collection is considered, since the two species are largely allopatric. Psorothamnus fremontii is confined to southeastern California, southern Nevada, northern and western Arizona, and south-central Utah; P. arborescens is found mainly west and north of P. fremontii in California, Nevada, and northwestern Mexico, except for var. pubescens, which occurs with P. fremontii in north-central Arizona and south-central Utah.

Selected References

None.

Lower Taxa

Psorothamnus fremontii var. attenuatus, Psorothamnus fremontii var. fremontii

Key

1	Leaflet blades obovate to linear-elliptic or linear-oblanceolate, (2–)3–15(–20) × 1.5–2(–4) mm.	Psorothamnus fremontii var. fremontii
1	Leaflet blades linear, (3–)5–25 × 0.7–1(–1.2) mm.	Psorothamnus fremontii var. attenuatus