Where Do Black Locust Trees Grow Naturally?

Black locusts are remarkably hardy hardwoods that have been introduced so widely outside their own native range that they were finally unceremoniously classed under “exotic.” If you’re curious about these trees with fragrant white flowers or if they do indeed have thorns, you’re reading the right article.

This Eastern tree of the United States has an ancient history and there are many facets to its range. Moreover, it is often confused with honey locusts, which are also thorny, but differ in many fundamental ways, being two distinct species.

The Natural Range of Black Locust Trees

Natural ranges of black locust trees extend to the major two regions of eastern United States. Most of their native range runs from the Appalachian Mountains in Pennsylvania to northern Georgia and Alabama. A second smaller population can be found in the Ozark Mountains within Missouri, Arkansas, and eastern Oklahoma. 

Despite restricted distributions in its native range, black locust has been widely planted and naturalized throughout North America and other temperate regions of the world. Presently black locust trees can be found growing somewhere throughout all of the continental United States, parts of Canada, Europe, parts of Asia, and beyond.

Does the Black Locust Tree Have Thorns?

Yes, black locust trees definitely have thorns, though they’re technically classified as spines rather than true thorns. These sharp protrusions develop in pairs at the base of leaf nodes along younger branches and stems. The spines on black locust trees typically measure between 1/2 to 1 inch long and can be quite sharp, serving as a natural defense mechanism against browsing animals.

These thorns are one of the distinctive features that help identify black locust trees in the wild. As the tree matures, the production of thorns often decreases on the main trunk and older branches, though they remain present on new growth.

Black Locust vs. Honey Locust: Which Locust Tree Has Thorns?

Both black locust and honey locust trees have thorns, but they differ significantly in appearance:

• Black locust thorns are relatively short (up to 1 inch), paired, and found primarily at leaf nodes on younger branches.
• Honey locust thorns are much more formidable. These trees develop large, branched thorns that can grow up to 8 inches long directly from the trunk and branches. These impressive thorns are often clustered in groups and can be quite menacing in appearance.

If you’re wondering which locust tree has the more dangerous thorns, the honey locust (Gleditsia triacanthos) wins by a significant margin. Its thorns are substantially larger, more numerous, and capable of causing serious injury. However, thornless cultivars of honey locust have been developed for landscape use.

Where Does Black Locust Grow Best?

Black locust trees are remarkably adaptable, which explains how they’ve managed to spread so widely beyond their native range. These trees thrive in:

• Full sun conditions
• Well-drained soil
• Disturbed areas where other vegetation might struggle
• Locations with moderate rainfall (though they’re drought-tolerant once established)

Black locust trees show particular vigor in open areas like abandoned fields, roadsides, and forest edges. They’re often among the first trees to colonize disturbed sites, playing an important role in ecological succession.

One reason black locust grows so successfully in diverse environments is its ability to fix nitrogen from the atmosphere through a symbiotic relationship with soil bacteria. This adaptation allows black locust to grow in poor soils where other trees might struggle, making it both a pioneer species and sometimes an invasive one outside its native range.

The Ecological Impact of Black Locust Trees

Knowing it by the difference between ranges where it grows naturally and where it has been established to grow speaks volumes, more so about how we perceive the trees ecologically. In the native Appalachian and Ozark ranges, black locust trees belong to an important resource for the ecosystem. In many areas introduced by the tree, they were found as invaders, outcompeting native plants. Black locust trees grow very quickly, able to sprout newly from roots, fix nitrogen, and are quite competent to give a rapid way for reclamation of disturbed sites or to stabilize or prevent erosion. However, these key traits can also lead to being a problem invader in some ecosystems.

Practical Uses for Black Locust Trees

Black locust has been widely planted for multiple practical purposes:

• The wood is exceptionally rot-resistant, making it valuable for fence posts and outdoor construction
• Its dense wood burns hot and clean, making excellent firewood
• The fragrant spring flowers are important nectar sources for honeybees
• They’re effective for erosion control and mine reclamation projects

Growing Your Own Black Locust

If you are considering planting black locust trees there are advantages and disadvantages. Thorns are one of the unique features of black locust trees; during their initial years, black locusts with their thorns become very difficult to handle. You want to think whether a thorny tree would be suited to your very residence, especially with children around. 

Check if black locust is invasive to your area before planting black locusts, as it could potentially be the case in some regions of the country, for example, if this frequently fast-growing perennial tree is endangering native ecosystems. 

On the flip side, black locust turns out to be a very beautiful and valuable tree species under certain conditions, growing fast, producing large sweet-scented flowers in summer, and providing a habitat for wildlife. 

To identify where the naturally occurring black locust trees grow will help us understand and appreciate better not only their ecological contribution in that native range but also the caution we should have while introducing black locust in other places. It is useful to know and understand the characteristics of black locust (Robinia pseudoacacia) versus a honey locust (Gleditsia triacanthos), to make a fully informed decision about the usage of these interesting and exasperating (thorns!) species in out garden as we try to identify a thorny tree in our backyard or decide whether or not to utilize black locust as a planting option.