Carya aquatica aka Water Hickory

Carya aquatica is water hickory, also called swamp hickory. This deciduous tree belongs to the walnut family. It grows wild in the central and southeastern United States. Its habitats include swamps, river bottoms, and land that floods. It forms part of wetland forests and helps clean floodwater runoff. Gardeners grow it for shade and wildlife near ponds and streams.

This slow-growing tree needs plenty of room. NC State gives heights of 80–100 feet [24–30 metres]. Its spread reaches 40–50 feet [12–15 metres]. RHS gives heights above 39 feet [12 metres]. Its listed spread is 13–26 feet [4–8 metres]. Some trees exceed 100 feet [30 metres]. The crown may be narrow and uneven or broadly branched. Mature trees cast dense shade. Young bark is smooth, with grey and brown tones. With age, it breaks into loose scales with reddish edges. Twigs are reddish brown, with yellowish buds.

The glossy green leaves grow in an alternate pattern. Each pinnate leaf has seven to fifteen curved, narrow leaflets. Their edges have teeth, and hairs line the veins beneath. Small yellow-green flowers appear in spring. Male flowers hang in slender catkins; females form short spikes. Flattened, oval nuts develop inside fuzzy yellow or brown husks. They ripen in autumn. Trees may take about twenty years to start bearing nuts. Hot summers help fruit production. Ducks, other birds, and small mammals eat the bitter kernels. Leaves feed several moth caterpillars, including luna and royal walnut moths.

Grow water hickory in full sun, though it tolerates some shade. Give it soil that stays moist through summer. It tolerates wet ground and periods of flooding. Moist, well-drained soil supports its best growth. Clay, loam, and sand suit it, with acid or neutral pH. NC State lists USDA zones 7–11; RHS rates it H6. Seeds need a cold, moist period before they sprout. Young trees soon form deep taproots and dislike root disturbance. Plant seedlings in their lasting site during their first year.

Pests seldom cause trouble, but several diseases can occur. These include crown gall, powdery mildew, and leaf spot. Seeds and root sprouts can spread the tree aggressively. Its wood serves as fuel and fencing material. The kernels are edible raw or cooked, but taste very bitter. PFAF reports no known hazards or medicinal uses. ASPCA lists it as non-toxic to dogs, cats, and horses.