Description from Flora of China
Slender herbs, annual, to 40 cm tall; stems 4-angled to flattened, 2-sulcate, with sides glabrous and angles thickened to winged and puberulent and/or scaberulous (var. corymbosa) or terete to flattened and sparsely to densely scaberulous to puberulent throughout (var. tereticaulis). Leaves subsessile; blade drying membranous, linear, narrowly lanceolate, or narrowly elliptic, 0.8-2 × 0.1-0.5 cm, adaxially sparsely scaberulous to glabrescent, abaxially glabrescent, base cuneate to acute, margins usually at least shortly revolute at least when dry, apex acute; secondary veins not visible; stipules fused to petiole bases, tubular, 1-2 mm, puberulent to glabrous, rounded to triangular, with 1-5(or 7) linear lobes or bristles 0.2-2.5 mm, these sometimes bifid. Inflorescence axillary, 1-flowered or usually cymose and 2-5-flowered, glabrous, pedunculate; peduncles 1(or 2) per axil, filiform, 1-16 mm; bracts lacking or stipuliform and 1-1.2 mm; pedicels slender, 2-12 mm. Flowers homostylous, pedicellate. Calyx glabrous to puberulent; hypanthium portion subglobose to narrowly ellipsoid, 0.5-0.8 mm; limb lobed essentially to base; lobes narrowly triangular, 0.5-1.2 mm, entire to ciliate. Corolla white or pink, funnelform to rotate; tube 0.8-1 mm, inside pubescent or glabrous; lobes spatulate-oblong to narrowly triangular, 0.5-0.8 mm. Anthers included, ca. 0.6 mm. Stigma 0.3-0.5 mm, included. Fruit capsular, subglobose, ovoid, or oblate, 1.2-2 × 1.2-2.2 mm, somewhat dicoccous, membranous, glabrous to puberulent, loculicidally dehiscent through flat to broadly rounded apex, beak when present to 0.5 mm, peduncles and pedicels usually elongating rapidly and markedly as fruit develop; seeds 20 or more, dark brown, angled, smooth. Fl. and fr. almost year-round.
These plants are low annual weeds found in highly disturbed habitats and show wide morphological variation between sites and usually among plants in one site in plant size, leaf width, number of peduncles per axil, and number of flowers per peduncle. The taxonomy of this and related species is complicated, and different authors have drawn very different conclusions (e.g., Sivarajan & Biju, Taxon 39: 665-674. 1990; Dutta & Deb, Taxon. Rev. Hedyotis. 2004). In particular, Hedyotis brachypoda, H. diffusa, and H. erecta are related and have been variously circumscribed. Here, these species are circumscribed generally though not completely following Sivarajan and Biju (loc. cit.) and W. C. Ko (in FRPS 71(1): 72, 75. 1999). However, W. C. Ko described the hypanthium of H. corymbosa as 1-1.2 mm in diam., which corresponds to H. diffusa in most recent classifications rather than H. corymbosa. The varieties recognized by W. C. Ko are presented here for reference.
Paddy fields, ridges of farmlands, humid grasslands; sea level to 900 m. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Sichuan, Taiwan, Zhejiang [Africa and tropical Asia; widely adventive in the Americas and the Pacific region].