Locust Tree Identification: Honey Locust vs Black Locust
Locust trees confuse people because the two most common species look almost nothing alike. Honey locust has delicate, feathery leaves and an open canopy that lets light through. Black locust has oval leaflets on a compound leaf and produces heavy clusters of fragrant white flowers in spring. Both are native to eastern North America, both grow fast, and both have thorns (in the wild, at least). But locust tree identification is straightforward once you learn the differences between these two species and their common cultivars.
This guide covers honey locust and black locust in detail — leaves, bark, thorns, flowers, pods, and growth habits — plus how to tell them apart at a glance.
Honey Locust Identification
The honey locust (Gleditsia triacanthos) is one of the most planted street and landscape trees in North America. Its fine-textured foliage and filtered shade make it a favorite in urban settings. Wild honey locusts are armed with branching thorns up to 8 inches long, but most planted specimens are thornless cultivars.
Honey Locust Leaves
Honey locust leaves are the tree’s most distinctive feature. They can be either:
- Pinnately compound: A central stem (rachis) with 15 to 30 small leaflets arranged on both sides, each leaflet about 3/4 to 1.5 inches long
- Bipinnately compound: The central stem branches into secondary stems, each carrying its own row of tiny leaflets
Many honey locusts produce both leaf types on the same tree. The bipinnate leaves look almost fern-like. Individual leaflets are so small that they don’t need to be raked in fall — they filter through grass and decompose quickly. This is one reason landscapers love the tree.
The leaves turn yellow in fall, but the color is subtle compared to maples or sweetgums. The tiny leaflets drop individually, creating less visible litter than most deciduous trees.
Honey Locust Bark and Thorns
Young honey locust bark is smooth and gray-brown. Mature bark develops long, flat-topped ridges separated by deep furrows, often with a slightly reddish-brown tint in the furrow bottoms.
The thorns on wild honey locusts are impossible to miss. They grow from the trunk and branches in clusters of three (the species name triacanthos means “three-thorned”). These thorns are stiff, sharp, and branching — some reach 8 inches or more. On the trunk, they can form dense masses of spines that make the tree look weaponized.
Almost all honey locusts planted in yards and along streets are the thornless variety Gleditsia triacanthos var. inermis, or cultivars like ‘Shademaster’ and ‘Sunburst’. These were bred to lack thorns entirely. If you find a locust with branching thorns on the trunk, it’s either a wild-type honey locust or a seedling that reverted.
Honey Locust Seed Pods
Honey locust pods are long, flat, twisted, and dark brown when ripe. They typically measure 6 to 18 inches and contain hard seeds surrounded by a sweet, sticky pulp — the “honey” in the common name. The pods hang in clusters and drop in fall, often littering the ground beneath the tree.
The pods are edible and were a food source for Indigenous peoples and early settlers. Deer, squirrels, rabbits, and cattle also eat them. Many thornless cultivars produce fewer pods than wild types, and some (‘Shademaster’) are mostly podless.
Black Locust Identification
Black locust (Robinia pseudoacacia) is a very different tree from honey locust despite sharing a name. It’s native to the Appalachian region and Ozark Plateau but has spread across the entire United States (and much of the world) since colonial times.
Black Locust Leaves
Black locust leaves are pinnately compound — never bipinnate like honey locust. Each leaf has 7 to 19 oval leaflets arranged in pairs along a central stem, with one leaflet at the tip. The leaflets are larger than honey locust leaflets, usually 1 to 2 inches long, with smooth margins and a rounded or slightly notched tip.
The overall effect is a medium-textured leaf that looks quite different from honey locust’s fine, ferny foliage. Black locust leaves are dark blue-green above and paler underneath.
At the base of each leaf stem, look for a pair of small spines. These are modified stipules and are present on most black locust branches. They’re much shorter than honey locust thorns (usually under 1 inch) and always come in pairs at the leaf nodes rather than in branching clusters on the trunk.
Black Locust Bark
Black locust bark is one of the tree’s best identification features. On mature trees, it forms deep, interlocking, rope-like ridges that look like braided or twisted cords running up the trunk. The color is dark gray-brown to nearly black, which gives the tree its common name.
This distinctive bark pattern is visible from a distance and unlike most other hardwoods. Combined with the compound leaves and paired thorns, it makes black locust easy to identify. If you’re learning to identify trees by their bark, black locust’s ropy furrows are among the most recognizable patterns you’ll encounter.
Black Locust Flowers
Black locust produces showy clusters of white flowers in late May to early June. The flowers hang in dense, drooping racemes 4 to 8 inches long, and they’re fragrant — the scent is sweet, almost like grape or wisteria. Black locust flowers are a major nectar source for honeybees, and “black locust honey” is prized for its light color and mild flavor.
Honey locust flowers are small, greenish, and inconspicuous. If you see a locust tree covered in white flower clusters, it’s black locust.
Black Locust Seed Pods
Black locust pods are flat, smooth, and dark brown, typically 2 to 4 inches long. They’re much shorter and neater than honey locust’s long, twisted pods. Each pod contains 4 to 8 small, hard, kidney-shaped seeds.
The seeds are toxic to humans and livestock if eaten in quantity. The bark, leaves, and young shoots are also toxic. This is another sharp contrast with honey locust, whose pods and pulp are edible.
Honey Locust vs. Black Locust: Side by Side
These two trees share a name but are easy to separate once you know what to look for.
| Feature | Honey Locust | Black Locust |
|---|---|---|
| Leaves | Pinnate or bipinnate, tiny leaflets (fern-like) | Pinnate only, larger oval leaflets |
| Thorns | Branching clusters on trunk (wild type) or thornless (cultivars) | Small paired spines at leaf nodes |
| Bark | Flat-topped ridges, moderate furrows | Deep rope-like, interlocking ridges |
| Flowers | Small, greenish, not showy | Large white clusters, fragrant |
| Pods | Long (6-18”), twisted, sweet pulp | Short (2-4”), flat, toxic seeds |
| Size | 60-80 ft tall, wide spreading crown | 40-80 ft tall, more upright and irregular |
| Spread | Native, planted widely | Native but aggressively invasive |
The quickest test: look at the leaf texture. If the leaflets are tiny and fern-like, it’s honey locust. If they’re 1-2 inch oval leaflets in matched pairs, it’s black locust.
Where Locust Trees Grow
Honey locust is native from Pennsylvania south to Alabama and west to Nebraska and Texas. It grows in bottomlands, riverbanks, and open woodlands. The thornless cultivars are planted throughout the United States and southern Canada as street trees and shade trees. They tolerate road salt, compacted soil, drought, and urban pollution better than most species.
Black locust is native to the Appalachian Mountains and Ozark Plateau. Since European settlement, it has spread to all 50 states and is considered invasive in many areas. It colonizes disturbed ground aggressively through root suckers, forming dense thickets. You’ll find it along roadsides, old fields, forest edges, and railroad corridors.
Both species prefer full sun and tolerate poor, dry soils. As legumes, they fix atmospheric nitrogen through root nodule bacteria, which lets them thrive in nutrient-poor ground where other trees struggle.
Common Locust Cultivars You’ll See
Most locust trees in landscaped areas are cultivars, not wild types:
- ‘Shademaster’ honey locust — Thornless, mostly podless, strong central leader. The most commonly planted street tree cultivar.
- ‘Sunburst’ honey locust — Thornless, with bright yellow-green new growth in spring that gradually turns green. Smaller than ‘Shademaster’.
- ‘Skyline’ honey locust — Thornless, broadly pyramidal crown, good fall color.
- ‘Purple Robe’ black locust — Dark pink-purple flowers instead of white. Planted ornamentally.
- ‘Frisia’ black locust — Golden-yellow foliage throughout the growing season. Popular in European gardens.
If you see a locust tree in a yard or along a street, it’s almost certainly a thornless honey locust cultivar. Black locust cultivars are less common in landscaping because the species spreads aggressively.
Identifying Locust Trees With Tree Identifier
Locust trees have compound leaves that trip up beginners. The Tree Identifier app takes the guesswork out of it. Photograph a leaf, a section of bark, or a flower cluster, and the AI will tell you whether you’re looking at honey locust, black locust, or something else entirely. The app identifies from leaves, bark, flowers, and fruit, so you can confirm during any season.
It also works offline, which is useful if you’re hiking through Appalachian forests where black locust is common and cell signal is spotty. Two free identifications per day let you try it without a subscription.
Frequently Asked Questions
Are locust trees toxic?
Black locust bark, leaves, and seeds are toxic to humans and livestock. Honey locust is not toxic — the pods and pulp are edible and were historically used as food. Always confirm the species before assuming safety.
Are locust trees invasive?
Black locust is considered invasive in many U.S. states. It spreads through root suckers and can form dense thickets that crowd out native plants. Honey locust is not typically invasive, though seedlings can pop up from pods.
How long do locust trees live?
Honey locusts typically live 100 to 150 years. Black locusts have shorter lifespans, usually 60 to 100 years, partly because they’re susceptible to the locust borer beetle which weakens the trunk over time.
Why do honey locust trees have thorns?
The thorns evolved as defense against large herbivores that are now extinct in North America, including mammoths and ground sloths that browsed on the tree. The long, twisted seed pods were likely dispersed by these megafauna. Today, cattle and deer eat the pods, but the thorns serve less purpose — which is why thornless cultivars grow fine without them.
Can you tell honey locust from black walnut by the leaves?
Both have compound leaves, but black walnut leaflets are larger (2-5 inches), have serrated edges, and release a strong spicy scent when crushed. Honey locust leaflets are much smaller (under 1.5 inches) and unscented. The leaf texture difference is obvious side by side.
Want to identify locust trees and other species with confidence? Try Tree Identifier — snap a photo of a leaf, bark, or flower and get an instant ID.
Elena Torres
Tree Identifier Team
