J. F. Gmelin, Syst. Nat. 2: 150. 1791.
Water-elm, planer tree
Leaves: petiole 3-6 mm. Leaf blade 3-8 × (2-)2.5(-4) cm. Flowers: if bisexual, ovary stalked, 1-locular, ovoid, tubercular; styles 2, reflexed. Fruits stalked, compressed, ca. 8 mm, leathery, hirtellous, covered with irregular warty excrescences. Seeds ovoid.
Flowering spring (Apr-May). Swamps, streams, lakes, alluvial flood plains, often forming large stands; 0-200 m; Ala., Ark., Fla., Ga., Ill., Ky., La., Miss., Mo., N.C., Okla., S.C., Tenn., Tex.
Planera aquatica is endemic to southeastern United States.