Herbs, annual, 15-20 cm tall. Root fibrous, 0.8-1 mm. Stems many from base, ascending or suberect, rarely prostrate, ca. 1 mm thick, usually glabrous, rarely with a few hairs when young. Leaves opposite; stipules interpetiolar, truncate, 0.7-0.9 mm, shallowly lacerate; petiole 1.5-2 mm; leaf blade oblong-elliptic, 0.7-3 cm × 0.3-1.2 mm, thickly papery, base slightly oblique, asymmetric, subrounded, margin sparsely crenate, apex obtuse, adaxially with a few purple spots. Cyathia axillary and terminal, single or in small cymes, peduncle to 4 mm; involucre narrowly campanulate, ca. 0.8 × 0.4-0.5 mm, glabrous, marginal lobes 5, triangular; glands 4, yellow-green, rounded to transversely elliptic, appendages white or pale pink, wider than glands, to 0.7 × 0.5 mm, margin entire to slightly undulate. Male flowers 5-15, exserted; anthers red. Female flower pedicellate, exserted from involucre; ovary smooth, glabrous; styles free; stigma slightly 2-lobed. Capsule 3-angular-ovoid, 2-2.5 × ca. 2.5 mm, smooth, glabrous; fruiting pedicel ca. 2 mm. Seeds ovoid-tetragonal, ca. 1.1 × 0.8 mm, blackish, each side with 3 or 4 transverse furrows; caruncle absent. Fl. and fr. Jan-Apr.

Wiggins 1964, Jepson 1993, Kearney and Peebles 1969

Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Erect to strongly ascending annual 5-60 cm tall with mostly glabrous but sometimes sparsely pilose herbage, stems simple to moderately branched at or near base. Leaves: Lanceolate to oblong, 4-20 mm, sometimes with a red blotch at center, margins evenly serrated, paler beneath than above. Flowers: Cyathia 0.4-.9 mm wide, solitary or in few-flowered cyme, peduncle 0.5-2 mm long, involucral glands 0.2-0.4 mm wide oval pink to maroon, appendages 0.3-0.6 mm wide, broader than long, white to pink, darkening with age; staminate flowers 4-15 per cyathium. Fruits: Strongly 3-lobed capsule, 1.6-2.1 mm long, with obtuse to rounded angles, glabrous. Ecology: Found on valley flowers, grassy slopes, washes, and rocky hillsides from 1,000-6,000 ft (305-1829 m); flowers throughout year under favorable moisture. Distribution: Widely distributed; Africa, Europe, e Asia, Australia; much of s N. Amer. and s US from UT and AZ east to MD; south through FL, Greater Antilles, MEX, C. Amer. and S. Amer. Notes: A highly variable plant in size, habit and shapes of leaves. Distinguished for the most part by being a mostly hairless annual, sometimes with sparse hairs; serrate leaves many longer than 15 mm; a hairless ovary larger than most species 2-2.5 mm long; and seeds with ridges. Could be confused with E. serpillifolia except it is more erect and larger in general, has more elongated leaves and ridges on seeds. Ethnobotany: Unknown for this species, other species in genera have medicinal use. Etymology: Euphorbia is named for Euphorbus, Greek physician of Juba II, King of Mauretania, hyssopifolia means having leaves like Hyssop. Synonyms: Chamaesyce brasiliensis, Euphorbia brasiliensis, Euphorbia hyssopifolia Editor: SBuckley 2010, FSCoburn 2015