Gleditsia triacanthos aka Honey Locust

Honey locust, Gleditsia triacanthos, is a deciduous tree in the pea and bean family, Fabaceae. Other common names include sweet locust and thorny locust. It is native to central and eastern North America, from Pennsylvania and southern Ontario west to Nebraska and South Dakota. Its range extends south to Texas, Florida and parts of northeastern Mexico. In the wild it grows along stream banks and in rich woods. It also grows beside roads and fields. It has naturalised in parts of central and southern Europe.

In gardens it usually reaches 50 to 60 feet (15 to 18 m) tall, with a similar spread. Wild trees can pass 80 feet (24 m), and a few exceed 130 feet (40 m). The main trunk is short and carries an open, spreading crown that is sometimes flat on top. The bark is grey-brown and breaks into long, smooth plates separated by furrows. Stout, often branched thorns grow on the trunk and branches. Some reach 6 inches (15 cm) or more. The zigzag twigs are shiny and reddish to greenish brown. The leaves are pinnate or bipinnate, 6 to 8 inches long, with 20 to 30 small leaflets. They are glossy bright green and cast only light shade. The leaves appear late in spring. They turn clear yellow in autumn and fall early.

Small, fragrant, greenish-yellow flowers open in May and June. They are not a major ornamental feature. Bees visit them for nectar. Flattened, twisted brown pods follow and can reach 18 inches (45 cm) long. They often stay on the tree into winter. In the UK, pods form mainly after long, hot summers.

The tree needs full sun and tolerates partial shade, but not full shade. It prefers deep, moist, fertile soil. It also copes with sand, clay, chalk, drought, salt and air pollution. Deer seldom damage it. It is hardy throughout the UK, rated H6, and to USDA zone 4. Turf grows well beneath its light canopy. This makes it useful as a lawn, street or native-garden tree. Its hard, durable wood has served for fence posts, railroad ties, tool handles and fuel. Native Americans made bows from it. It also supports the caterpillars of the silver-spotted skipper.

The thorns are dangerous, and the falling pods are messy. For these reasons, most planted trees are thornless forms. The species can sucker into dense thickets. It may also become a weed in pastures, and cutting makes it sprout more. Pests include borers, webworms, bagworms, spider mites, leaf miners and the pod gall midge. The gall midge deforms leaves and can kill small shoots. Diseases include cankers, leaf spots, powdery mildew, rust, witches' broom and honey fungus.

The sweet pulp inside the pods is edible raw or cooked. People have made it into sugar. Young seeds taste like raw peas. Roasted seeds have served as a coffee substitute. The plant does contain some potentially toxic compounds. However, the ASPCA lists it as non-toxic to dogs, cats and horses.