Duration: Perennial

Nativity: Native

Lifeform: Subshrub

General: Herbaceous perennials, to 15 cm tall, (usually low-growing), stems several, erect to decumbent, herbage glabrous, plants with a deep-set taproot.

Leaves: Opposite, lanceolate to ovate, 3-11 mm long with acute tips, margins entire.

Flowers: Monoecious, borne within a calyx-like involucre (cyathium), involucres campanulate to turbinate, to 1.5 mm in diameter, each involucre surrounds a naked pistillate flower surrounded by 5 glomerules of 1-5 or more naked staminate flowers, (totaling 25-35), involucre margins with 1-5 nectariferous glands, these oblong, reddish, to 1 mm long and half as wide or less, subtended by white petaloid appendages with crenate margins and obtuse tips, involucres borne solitary at the nodes.

Fruits: Capsules, subglobose, to 2.5 mm long, 3-celled, nodding. Seeds quadrangular, to 2 mm long, white, 3 per capsule.

Ecology: Found from 4,000-7,500 ft (1219-2286 m); flowering May-September.

Distribution: Arizona, California, Nevada, New Mexico, Texas

Notes: The glabrous herbage, ovate to lanceolate, entire leaves 3-11 mm long with acute tips, and white, quadrangular seeds help identify this species. Kearney and Peebles, who list this species as E. fendleri var. chaetocalyx, note that the variety freely integrades with the typical E. fendleri, which has wider leaves with obtuse tips, usually about as wide as long, and petaloid appendages which are narrowly deltoid with entire margins.

Ethnobotany: There is no use recorded for this species, but other species in this genus have uses.

Etymology: Euphorbia is named for Euphorbus, Greek physician of Juba II, King of Mauretania, while the meaning of chaetocalyx is Unknown

Synonyms: Chamaesyce chaetocalyx

Editor: LCrumbacher 2012