Carya cordiformis aka Bitternut

Bitternut hickory, Carya cordiformis, is a deciduous tree in the walnut family, Juglandaceae. It grows wild from eastern Canada through the central and eastern United States. Its range runs west to Nebraska and south to Texas and Florida. In the wild it favours moist woods, river bottoms and stream banks, though it also reaches some drier uplands.

In gardens it usually reaches 50 to 80 feet (15 to 24 m) tall with a spread of around 50 feet (15 m). Exceptional trees can pass 100 feet (30 m). The form is upright and fairly narrow, with an oval or rounded crown. Trees growing among others develop long, straight trunks and small crowns. In the open the trunk is shorter and the crown wider. The bark starts smooth and grey with a faint yellow tint. With age it breaks into narrow, shallow scaly plates, but stays less rough than most hickories.

The leaves are pinnate, 6 to 12 inches (15 to 30 cm) long, with five to nine toothed, lance-shaped leaflets. They turn a clear yellow to gold in autumn. The tree leafs out late and drops its leaves early. Its light, open shade lets lawn grass grow beneath it. In winter you can recognise it by its long, scaly, sulphur-yellow buds.

Male and female flowers appear on the same tree in April and May. The males hang in greenish-yellow catkins 3 to 5 inches (8 to 13 cm) long. The females form tiny spikes at the shoot tips, and neither is showy. The fruit is a roughly round nut about an inch (2.5 cm) long, with a thin shell. A four-winged husk with yellowish hairs covers it. Nuts ripen in October, but trees rarely bear before about 30 years of age.

This hickory grows best in deep, rich, moist but well-drained soil. It will take full sun or part shade but does poorly in deep shade. Sources rate it hardy in USDA zones 4 to 9 and RHS H6. A long taproot makes established trees hard to move. Sow seed or plant young trees where they will stay. The tree needs plenty of room, so it suits parks, large properties and naturalised woodland. It hosts the caterpillars of luna moths and the hickory horned devil. The hard, shock-resistant wood has served for tool handles, wheels, furniture and firewood. People also use it to smoke ham and bacon. Growers sometimes use seedlings as rootstock for pecans.

Pests include hickory bark beetle, pecan weevil, borers and twig girdlers. Diseases appear now and then. These include anthracnose, powdery mildew, leaf spot, leaf blotch, catkin blight, crown gall and white heart rot. Large trees shed many twigs, leaves and nuts, which can make a mess. The kernel is edible but very bitter and astringent, and even squirrels tend to ignore it. The ASPCA lists the tree as non-toxic to dogs, cats and horses.