General: Whitemargin Sandmat (Chamaesyce albomarginata) is low-growing, spreading perennial forb that hugs the ground to form mats about 18-inches across. The small, rounded leaves are paired. Cyathia ("flowers") emerge from leaf nodes, 1 cyathia per node. Bracts emerging from beneath the cyathia have white margins, giving the appearance of white flower petals. Fruit grows on a stalk from the center of the cyathia. Fruit without hairs, 2–2.5 mm long.

Whitemargin Sandmat is a common component of shrub communities in washes and on bajadas in the Lower Sonoran (Creosote-Bursage Flats) and Upper Sonoran (Mojave Desert Scrub) life zone.

Family: Spurge (Euphorbiaceae).

Other Names: Euphorbia albomarginata, Rattlesnake Weed

Plant Form: Spreading ground mat.

Height: Usually about 1-2 inches, about 5 inches.

Stems: Thin, prostrate, glabrous, fork repeatedly as the plant spreads. Release milky sap when broken.

Leaves: Opposite, round to oblong, 1/3-inch long, entire.

Flowers: Blooms spring to fall. Flowers small and nondescript (no petals), but surrounded by a white bract that gives the appearance of white petals.

Seeds: The fruits are three-sided seed pods.

Habitat: Dry, well-drained sandy and gravelly soils in washes, desert flats, and bajadas.

Elevation: To about 7,500 feet

Distribution: California to Utah and Louisiana, and south into Mexico.

Comments: Although this is a perennial forb, the above-ground parts usually dry up and completely blow away during later summer.