Gleditsia triacanthos Seeds | Honey Locust

Honey Locust (Gleditsia triacanthos) seed — Honey Locust (*Gleditsia triacanthos*): Fabaceae, subfamily Caesalpinioideae (legume family), native to The centre and east of North America from Pennsylvania and southern Ontario west to Minnesota, Nebraska and Texas, and south to the Gulf coast — most at home on moist river bottom ground and alluvial flats, and now planted far beyond its natural limits.

LATIN NAME: Gleditsia triacanthos

COMMON NAME: Honey Locust

Plant Profile

The species epithet triacanthos means three-spined, and the thorns explain it. They are not surface prickles but woody branch systems that rise out of the trunk wood itself, glossy red-brown when young and grey when old, often dividing into three points and reaching the length of a hand. Because they are made of wood they are not shed, and a mature tree on open ground may wear hundreds of them along the lower trunk, the perfect hedge for a tree that also feeds cattle.

The name comes from the fruit, not the flower. Pods run from fifteen to forty centimetres, flattened and often twisted and rippled along one edge, dark brown when ripe, and hung through the winter on the female trees. Split one open and the seeds sit in a sticky, pale, sweet pulp that tastes faintly of honey and is eaten by cattle, deer, possums and raccoons. It is the pulp, not the seed, that made the tree worth planting in a pasture.

For all its family, this tree does not fix nitrogen. Gleditsia belongs to the caesalpinioid line, and nearly all of that group lack the root nodules that house rhizobia, so a honey locust does not enrich the soil the way a black locust or a clover ley does. It tolerates poor ground and drought, but it is a consumer of nitrogen rather than a supplier, and an orchard plan that relies on it to feed its neighbours will disappoint.

Science & Biotechnology

Inside the seed, the endosperm is not starch but a galactomannan gum, closely related to the locust bean gum matured from carob seed. It swells in cold water to a stiff, clear gel, and it has been examined as a thickener and stabiliser for food and for textile printing pastes, where a gum that thickens without heat has obvious advantages. The pods also carry saponins, and the seed is bitter enough that it is not a food crop despite the sweet pulp around it.

Uses & Benefits

Outside North America the same toughness reads differently. In parts of South Africa, Australia and southern Europe the species has escaped cultivation along rivers and roadsides, spread by cattle and by floods, and formed thickets that are expensive to clear. A tree that shrugs off drought, salt, flooding and compaction will do the same in a country where nothing eats the pods and the seedlings have no competition.

The wood is hard, heavy, strong and remarkably durable in the ground, and it takes a fine finish. It was cut for fence posts, rails, pallets and railway ties, and the older furniture trade valued it for turned work and interior joinery where a strong, shock-resistant hardwood was wanted. The trouble is the tree’s habit: it grows as scattered individuals with thorny trunks, so there is rarely a stand worth felling and most of the timber is used where it falls.

Growing from Seed

Almost every honey locust in a modern street came from a selected thornless, near-fruitless clone grafted or budded onto seedling stock. Named selections such as Sunburst, with its gold new growth, Shademaster and Skyline were chosen for a straight trunk, a light airy crown and no pods to drop on a pavement, and they are raised in budded rows in dedicated nurseries. Their fine twice-compound foliage casts a dappled shade that grass will grow under, which is why the species became a standard for car parks and boulevards.

Sow into deep cells or a prepared seedbed in spring, and deal with the coat before you start. Pour water just off the boil over the seed and leave it to cool overnight, or nick the coat with a file on the side away from the embryo; either treatment lets water in and evens out sprouting across the lot. Sow about two centimetres deep in a free-draining loam and grit mix, and keep the bed moist but not wet, because waterlogged seed rots. Space the rows wide enough to walk between and the plants a hand and a half apart in the row, and thin the seedlings once they stand a hand tall, keeping the straightest. Give them full sun and plenty of room; the taproot goes down fast and a crowded seedling bends.

Cut out any seedling that shows thorns if you are raising stock for a garden, and do it before the thorns harden. Feed lightly in the first summer and not at all in late summer, so the wood ripens before the cold. Water through the first dry season, mulch the row to hold moisture, and stake the young tree for its first two winters against wind rock. The species is broadly free of serious disease, though trunk borers and the mimosa webworm can mark the foliage in hot years; a tree in good vigour shrugs both off.

Our Take

I would plant a named thornless clone in a small garden every time and save the seedling material for a hedgerow or a paddock. If the armed habit is what you want, the Asian Chinese honey locust is even more formidable and carries soap in its pods, while black locust gives you the nitrogen fixation this tree lacks. For a thornless legume with a fine pinnate leaf, Judas tree is the gentler choice. Nick the coat, sow deep, and thin hard.

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