Shrubs (evergreen), 50–200 cm. Stems profusely branched; glabrate or puberulent (bark corky, twigs smooth). Leaves: petiole 1–3 cm; leaflets 3, blade oblong-elliptic, 1.5–4.5 × 0.4–1.3 cm, margins serrate, apex acuminate to obtuse, surfaces glaucous. Racemes 1–3 cm (6–40 cm in fruit); bracts unifoliate, obovate to spatulate, 2–15 mm. Pedicels 7–15 mm (thickened in fruit). Flowers: sepals persistent, connate ca. 1/2 of length, green, lanceolate, 4–7 × 2.2–4 mm, margins entire, glabrous; petals yellow, ovate-elliptic, 8–14 × 4.2–5 mm, (apex acute); stamens yellow, 15–25 mm; anthers 2–2.5 mm; gynophore (reflexed), 10–20 mm in fruit; ovary 3–6 mm (often aborting in bud); style 0.9–1.2 mm. Capsules (tardily dehiscent), usually inflated,(valves sometimes 3), 20–30 × 6–12 mm, smooth. Seeds 5–25, dark brown, obovoid, 6–7 × 5–6 mm, smooth.
Ariz., Calif., nw, w Mexico.
Varieties 3 (3 in the flora).
Peritoma arborea is woody and is variable in fruit size and shape. The large variability in fruit shape has led to the naming of varieties (L. D. Benson and R. A. Darrow 1945).