Stems usually with 5+ lateral branches, these often branched, glabrous. Leaf blades: both surfaces glabrous; vein reticulum clearly visible abaxially. Cymules with 1 staminate and (1–)2–3(–5) pistillate flowers. Pistillate flowers: sepals linear-lanceolate or narrowly spatulate, (0.7–)0.8–1(–1.4) × 0.2–0.3 mm, apex acute; nectary cupular, unlobed, enclosing ovary 1/3–1/2 length at anthesis.

Flowering and fruiting summer–fall. Open, moist areas such as stream banks, lake and pond margins, forest openings, depressions in grasslands, disturbed sites; 0–600 m; Ala., Ark., Del., D.C., Fla., Ga., Ill., Ind., Kans., Ky., La., Md., Miss., Mo., N.J., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va.; Mexico; West Indies; Central America; South America; introduced in se Asia.

Subspecies caroliniensis is found almost throughout the range of Phyllanthus caroliniensis. In Florida, it reaches its native southern limit in Hillsborough County [it was collected on Key West once in the late nineteenth century (Curtis 185, GH), where it presumably was an introduced waif]. It has also been found as a garden weed in San Diego, California (Rebman 7115, SD), and may become established in that state.