Trees, evergreen, up to 20 m tall; branchlets with distinct nodes, glabrous. Leaves long petiolate; stipule solitary, narrowly ovate, enclosing apical bud, caducous, leaving annular scar at each node; leaf blade tricuspidate or simple, broadly ovate-rounded, leathery, base cordate, margin entire, venation actinodromous. Inflorescence densely spicate, terminal or leaf-opposed, pedunculate, many-flowered. Flowers bisexual, adjacent flowers united at base. Floral cup adnate to ovary. Sepals usually 5, imbricate, ovate-rounded, unequal. Petals usually 5, white, linear-liguliform, subfleshy, straight in bud. Stamens 10–13 (but see comment below), filaments short, stout; anther thecae 2-sporangiate, each dehiscing by 2 valves, connective protrusion massive, stamens and staminodes fused with petals into a tube. Ovary semi-inferior; ovules 6 per locule; styles very short. Capsules ovoid-globose, dehiscing above middle by two 2-lobed valves; exocarp subfleshy, endocarp woody. Seeds more than 1 per carpel, ellipsoid; seed coat thick and hard; endosperm fleshy; embryo situated in middle. 2n = 26.

The stamen number in Mytilaria is uncertain. Chang (Sunyatsenia 7: 69. 1948, and in FRPS 35(2): 50. 1979) gave it as 10–13, but the collection W. T. Tsang 22180 (P) from Guangxi has 5 stamens and 5 staminodes.

One species; China, Laos, N Vietnam.