Plants annual. Stems prostrate, much branched in large plants, forming loose mats, elongate, glandular-pubescent or glabrous. Leaves: petiole 1–6 cm; blade ovate, elliptic, or rhombic, 1.5–6.8 × 0.8–4.7 cm, margins entire to ± repand and undulate, surfaces glandular-puberulent to glandular-villous, usually ± glaucous. Inflorescences: peduncle longer than subtending petiole; bracts lanceolate to ovate, 5–7 × 3–5 mm, papery, glandular-puberulent to viscid-villous; flowers 8–27. Perianth: tube magenta to greenish, 6.5–18 mm, limb magenta, 6–16 mm diam., throat surrounded by white to yellowish white eyespot. Fruits ± obdeltate in profile, 6–12 × 6–16(–24) mm, indurate, smooth, not rugose veined, apex beaklike; wings 5, not folded, poorly to very well developed, from slightly shorter than beaklike apex of body to prolonged beyond beak, thin, without cavities.
B.C., Calif., Oreg., Wash., Mexico (Baja California).
Varieties 3 (3 in the flora).
S. S. Tillett (1967) stated that Abronia umbellata is sufficiently similar to the inland A. villosa that without information regarding locality some specimens would be very difficult to identify. He also considered A. umbellata subsp. alba (Eastwood) Munz, subsp. platyphylla (Standley) Munz, and subsp. variabilis (Standley) Munz, A. insularis Standley, and A. neurophylla Standley to be introgressive hybrids of A. umbellata with A. maritima.
The name Abronia gracilis Bentham has appeared in regional floras and treatments of Nyctaginaceae since Standley’s continental treatment (1918). S. S. Tillett (1967) stated that the taxon was reported for San Diego County, California, but cited no documenting specimens. I. L. Wiggins (F. Shreve and I. L. Wiggins 1964) considered only A. gracilis subsp. platyphylla (Standley) Ferris to enter the United States, in San Diego County, an entity considered by Tillett to be an intergrade between A. umbellata and A. maritima. The distinctions among A. gracilis, A. umbellata, and A. villosa are subtle at best, and the group is in need of careful study.
|1||Fruit wing tips often prolonged beyond fruit apex; flowers 7-10 mm||Abronia umbellata var. acutalata|
|1||Fruit wing tips terminating below or extending to fruit apex; flowers 6.5-18 mm||> 2|
|2||Flowers 6.5-10 mm; wings of fruit poorly to moderately developed, if developed, tapering to fruit apex||Abronia umbellata var. breviflora|
|2||Flowers 12-18 mm; wings of fruit well developed, truncate or tapering to fruit apex||Abronia umbellata var. umbellata|