Oenothera claviformis Torrey & Frémont subsp. yumae P. H. Raven, Univ. Calif. Publ. Bot. 34: 104. 1962 (as clavaeformis); Camissonia claviformis (Torrey & Frémont) P. H. Raven subsp. yumae (P. H. Raven) P. H. Raven

Herbs strigillose, often densely so, sometimes also glandular puberulent distally. Stems 5–40 cm. Leaves: blade lateral lobes poorly or well developed, terminal lobe lanceolate, to 6.5 × 2 cm, margins irregularly sinuate-dentate. Flowers opening at sunset; buds usually without free tips, sometimes with apical free tips less than 1 mm; floral tube orange-brown inside, 2.5–4 mm; petals pale yellow, fading reddish or not changing color, 3–5 mm. 2n = 14.

Flowering Feb–May. Very arid dunes and sandy flats, with Ambrosia dumosa and Larrea tridentata; 0–300 m; Ariz., Calif.; Mexico (Baja California, Sonora).

Subspecies yumae is known from southeastern Imperial County, California, Yuma Desert, Arizona, and from El Gran Desierto to Puerto Peñasco in north­western Sonora, and in northeastern Baja California. The subspecies is probably from hybridization between subspp. aurantiaca and peirsonii; it intergrades with subsp. aurantiaca and rarely hybridizes with Chylismia brevipes subsp. arizonica.