Sida 3: 402, fig. 4. 1969.
Caudices not developed; roots often long and rhizomelike, lignescent, tuberiferous. Stems usually several-branched distally, 20–55 cm, faces subequal, angles narrowly winged, internodes and nodes hirsute-villous, hairs gland-tipped. Leaves sessile; blade narrowly elliptic or narrowly oblong to narrowly oblanceolate or linear, 1.5–4 cm × 1–5 mm, lateral-veins relatively short or, in narrower leaves, absent, margins entire or minutely crenulate, ciliate, with gland-tipped hairs, apex sometimes apiculate, surfaces sparsely to moderately hirsute, hairs gland-tipped. Inflorescences diffuse, not obscured by bracts. Flowers: hypanthium globose, longer than the constricted neck, (4–) 5–7 (–8) mm, sparsely hirsute-villous, hairs gland-tipped; calyx lobes narrowly triangular, apices acute; petals spreading, pink to lavender-rose or purple, 1.1–1.2 cm; anthers curved, 4–5 mm. Seeds 0.7 mm, surfaces with 3–5 prominent, broad, symmetrical or tortuous longitudinal ridges or contiguous, domelike tubercles in rows. 2n = 22.
Phenology: Flowering Jun–Aug(–Sep).
Habitat: Inlet, pond, and lake shores, lime sinkpond margins, interdune swales, depressions, borrow pits, sandhills, longleaf pine savannas, slash pine flats, longleaf pine-turkey oak woods.
Elevation: 0–50 m.