Herbs perennial. Roots fusiform or conic. Stems clustered, 2--10 cm, glandular hairy in 2 lines or yellow or densely white glandular hairy. Leaves diffusely paired; petiole 2--5 mm; leaf blade lanceolate, elliptic, obovate, or saccate, 5--10 × 3--5 mm, granular, sparsely glandular pubescent or densely villous, midvein impressed, base cuneate, apex rounded or obtuse. Flower solitary or cymes few flowered; bracts similar to leaves but smaller. Pedicel 1--4 cm, sparsely glandular hairy. Sepals 5, greenish abaxially, ovate or lanceolate, 4--7 × 2--3 mm, sparsely glandular pubescent or densely villous, midvein impressed, base broadened, margin narrowly membranous, ciliate, apex acute. Petals 5, white, obcordate, ca. 2 × as long as sepals, base narrowly cuneate, apex rounded or bifid nearly to middle. Floral disc with 5 fleshy glands. Stamens 10, longer than sepals; anthers brown or green. Ovary ovoid, ca. 1.5 × 1.2 mm. Styles 4 or 5 (in female flowers), ca. 1.5 mm. Fl. Jul--Aug.

A related species, which has not been validly published ( Arenaria galiiformis C. Y. Wu in W. T. Wang et al., Vasc. Pl. Hengduan Mount. 1: 402. 1993), differs from A. weissiana in having stems dichotomously branched, slender, hard; leaves usually in whorls of 4, blade 5–10 × 3–8 mm, thickened, both surfaces white powdery, densely hairy, base attenuate, apex obtuse; sepals densely and shortly glandular pubescent; petals broadly ovate or suborbicular, apex emarginate; ovary ovoid, 2–3 mm; and styles 3, ca. 2.5 × as long as ovary. It grows in rock crevices, from 4200–4300 m, in SW Sichuan.

Three varieties of Arenaria weissiana have been recognized. Field studies are needed to better characterize these entities.

* Alpine meadows, shifting screes, rock crevices; 2800--4800 m. Sichuan, NW Yunnan.