Duration: Annual

Nativity: Native

Lifeform: Forb/Herb

General: Annual herb; herbage usually glabrous and sometimes glaucous; stems freely branching, prostrate (sometimes erect) and forming mats, 5-35 cm long; slender taprooted

Leaves: Usually 3-4 (10) mm long, oblong, ovate or obovate, sometimes serrulate, at least toward the tip; often wider below the middle and tapering to the apex.

Flowers: Cyathia solitary at nodes, 1 female flower surrounded by 5-18 male flowers, involucre about 1 mm in diameter, the involucre campanulate; glands oblong with narrow, white, entire or subdentate appendages.

Fruits: Capsules 1.5-2 mm long, sharply 3-angled, glabrous; seeds quadrangular, ovoid, 1-1.5 mm long, white to brown; reticulately wrinkled to nearly smooth, testa dark gray under whitish outer coat.

Ecology: Found on open, moist to dry places, on various substrates, tolerant of alkali, sometimes weedy in habit from lowlands to mountains; 3,000-7,000 ft (915-2135 m); flowers May-September.

Distribution: Most of N. Amer., almost every state in the US; south to c MEX.

Notes: This group of Euphorbia is in the Chamaesyce clade and used to be in its own genus. They are typically low-growing; have opposite leaves with non-symmetrical bases; milky sap and small flowers (actually inflorescences called cyathia) which produce a much larger ovary or fruit with three sections which hangs over the flowers. E. serpyllifolia is widespread and common at mid-elevations throughout much of the west. Distinguished by being a completely hairless, prostrate to ascending annual with non-linear leaves possessing serrate margins; cyathia are solitary from axils and not clustered; capsules <2 mm and seeds with no ridges.

Ethnobotany: White Mountain Apache chew plant as saliva sweetener. Miwok make poultice for snakebites from plant. Navajo make cold tea for stomachache, diarrhea, and for ceremonial purposes. Poultice also made to treat poison ivy, warts or toothaches.

Etymology: Euphorbia is named for Euphorbus, Greek physician of Juba II, King of Mauretania, while serpyllifolia means with leaves like those of thyme.

Synonyms: Chamaesyce albicaulis, C. neomexicana, Euphorbia neomexicana, Euphorbia serpyllifolia

Editor: SBuckley 2010, FSCoburn 2015