Trees , to 46 m. Bark light gray or brownish, exfoliating, separating freely into long strips or broad plates, less commonly with small platelike scales. Twigs brown to reddish brown or black, slender, villous becoming glabrous. Terminal buds brown, reddish brown, or black, oblong, 8-10 mm, yellow-scaly, villous; bud scales valvate; axillary buds protected by bracteoles fused into hood. Leaves 4-6 dm; petiole 3-8 cm, villous becoming glabrous. Leaflets (5-)9-11(-13), lateral petiolules 0-2 mm, terminal petiolules (2-)6-10(-14) mm; blades ovate-lanceolate, often falcate, 2-19 × 1-4 cm, margins finely or coarsely serrate to entire and wavy, without tufts of hairs, apex acuminate; surfaces abaxially villous with unicellular and 2-8-rayed fasciculate hairs along midrib and secondary veins, densely scaly in spring with large peltate scales and small round, irregular, and 4-lobed peltate scales, adaxially villous along midrib near base, glabrous between veins. Staminate catkins pedunculate, to 21 cm, stalks villous, bracts scaly; anthers without hairs. Fruits brown, bronze, or black, obovoid, compressed, 1.5-3 × 1.5-2.5 cm; husks rough, 1 mm thick, dehiscing to base or nearly so, sutures winged; nuts chocolate brown, broadly obovoid, compressed, 2-angled, verrucose; shells thin. Seeds bitter. 2 n = 32. Flowering spring. Bayous, river flood plains, bluffs, and levees, temporarily flooded bottomlands; 0-200 m; Ala., Ark., Fla., Ga., Ill., Ky., La., Miss., Mo., N.C., Okla., S.C., Tenn., Tex., Va. Carya aquatica hybridizes with C . illinoinensis ( C . × lecontei Little [= Hicoria texana Le Conte]) and is reported to hybridize with the tetraploid C . texana [ C . × ludoviciana (Ashe) Little].
Bark separating into long scales; winter-buds brown; lfls (7)9-11(-15), lanceolate, the terminal long-cuneate at base and sessile or nearly so; frs 1-4, strongly flattened, ovoid or obovoid, 2.5-3.5 cm, narrowly winged, splitting to the base at maturity; nut obovoid to nearly discoid, 1.5-3 cm, half as thick as wide, strongly wrinkled, short- pointed; kernel bitter; cotyledons bifid; 2n=32. Swamps and flood-plains; se. Va. to Fla. and Tex., and n. inland to s. Ill. and se. Mo.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.