Chamaesyce serpyllum Small, Fl. Florida Keys, 81, 155. 1913; C. deltoidea subsp. serpyllum (Small) D. G. Burch

Stems prostrate, loosely mat-forming, canescent, hairs appressed, less than 0.1 mm. Stipules canescent with appressed hairs; petiole canescent with appressed hairs; blade 2–5(–7) × 1–2.5(–5) mm, 2 times longer than wide, surfaces silver-green, canescent with appressed hairs. Involucre canescent with appressed hairs. Pistillate flowers: ovary canescent with appressed hairs. Capsules canescent with appressed hairs.

Flowering and fruiting year-round. Open pine rocklands; of conservation concern; 0–10 m; Fla.

Subspecies serpyllum is restricted to pine rockland on Big Pine Key, Monroe County.