Diminutive herb, to c. 15 cm high, sometimes unbranched. Leaves linear or narrowly oblong, 3–10 mm long, 0.5–1.5 mm wide, margins minutely serrulate, acutely tapered but blunt at the very apex. Flowers on pedicels 1–3 mm long; calyx 2–4 mm long, persisting and the lobes spreading star-like after the capsule has fallen; corolla c. one-third as long as calyx, lobes broadly obovate, with broadly acuminate apex, white; stamens attached at throat of corolla tube. Capsule broadly ovoid or c. spherical, c. 2 mm diam.; seeds c. elliptic, 1 mm long, dark red-brown, concave on inner face, rounded and transversely ridged dorsally. Flowers Aug.–Oct.
Flowers are less than 1/8 inch across when the lobes are fully spreading and about 1/16 inch across when they are more erect.Leaves are usually less than ¼ inch long and 1/8 inch wide, but may be up to 1/3 inch long, toothless and hairless, and mostly alternate along the stem though lower leaves may be opposite. Shape is elliptic to egg-shaped, sometimes widest above the middle, pointed at the tip and narrowed to a stalk-like base. Stems are smooth and simple or branched, erect or prostrate but rising at the tip (decumbent) and rooting at the nodes, forming colonies.