The native species of the Honey Locust tree, Gleditsia triacanthos, is thorny. This deciduous tree, native to central North America, is characterized in the wild by sharp spines. While the tree is known for its open canopy and resilience, the presence of these thorns sets the wild species apart. The thorns contributed to the tree’s common name, the Thorny Locust.
Anatomy of the Honey Locust Thorns
The thorns found on the native Honey Locust are substantial, woody, modified branches. These structures are usually reddish-brown, rigid, and extremely sharp, growing directly out of the trunk and lower branches. A single thorn often measures between two and eight inches long, sometimes reaching up to twelve inches.
A defining characteristic of these spines is their arrangement, as they frequently branch out into clusters. The species name triacanthos refers to this feature, often meaning “three thorns,” though clusters can be larger and denser on the main trunk. These heavy, branched thorns evolved as a deterrent against large browsing animals. Scientists hypothesize the thorns protected the tree from now-extinct Pleistocene megafauna, such as the mastodon, which would have fed destructively on the tree’s bark and foliage.
Understanding Thornless Cultivars
The Honey Locust trees most commonly encountered in urban and suburban landscapes are thornless. Commercial growers cultivate specific varieties, known as cultivars, which are selections bred for desirable traits. The primary cultivar used in landscaping is Gleditsia triacanthos var. inermis, a naturally occurring variety that lacks the thorns of the wild species.
The term inermis translates from Latin as “unarmed” or “thornless.” These thornless trees are genetically stable and often propagated by grafting, a technique that joins a piece of the desired variety onto the rootstock of another tree. This process ensures the resulting tree retains the specific thornless characteristic. Cultivars like ‘Sunburst’ and ‘Shademaster’ are favored due to their tolerance for urban conditions, including air pollution, poor soil, and drought.
Safety Concerns and Removal
The large, woody thorns of the wild Honey Locust present safety concerns in areas frequented by people or machinery. The rigid, sharp spikes inflict deep puncture wounds, carrying a high risk of infection from introduced soil bacteria. Furthermore, the thorns are strong enough to puncture vehicle and tractor tires, making the tree a hazard in agricultural settings or along driveways.
When managing or removing a thorny Honey Locust, specific safety precautions are necessary. Protective gear, including thick leather gloves, heavy-duty clothing, and puncture-resistant boots, should be worn to mitigate injury. Cutting down the tree requires careful handling of the debris, as fallen branches and stray thorns can litter the ground for years. Stumps must be treated with herbicide to prevent aggressive re-sprouting, which results in dense thickets of young, thorny growth.