Locust Branch

Invasive Watch: Locust Trees

Aug. 14, 2020
When tall-growing vegetation like honey locust or black locust make contact with utility power lines, service interruptions regularly occur. Learn how to protect system reliability by properly identifying and treating these similar brush species.

What to Look For

Honey locust (Gleditsia triacanthos) is a deciduous and thorny legume tree that is aggressive and fast-growing. The tree’s bark is grayish-brown and furrowed with long, scaly ridges. Honey locusts feature alternating oval leaves that grow anywhere from 6 to 8 inches in length.

Comparatively, black locust (Robinia pseudoacacia) is an early successional legume tree that is also deciduous, thorny and fast-growing. When mature, black locust bark is dark brown and deeply furrowed. Its oval-to-rounded leaves alternate along the stems and feature dark-green coloring on the top with pale hues on the underside. Both honey locust and black locust produce white fragrant flowers that appear from May to June.

Where They Are Found

Whereas honey locust can be located from the western slopes of the Appalachian Mountains to the eastern edge of the Great Plains, black locust is native to the southeastern United States and often found throughout the lower slopes of the Appalachian Mountains as well as regions of the Midwest. Both species pose a serious threat to native vegetation on utility rights-of-way and upland forest edges.

In terms of reproduction, honey locust spreads rapidly from seeds and outcompetes native vegetation by forming dense thickets of trees, while black locust reproduces rapidly by root suckering and stump sprouts, which can regrow to form expansive tree groves. As both species can grow anywhere from 40 to 100 feet in height at full maturity, they can easily extend into utility power lines when left untreated.

How to Treat Locust Species

To effectively control either of these two problematic species of locust, apply a mix of TerraVue™ herbicide (2.85 ounces per acre) and Garlon® 4 Ultra herbicide (16 to 32 fluid ounces per acre) after full leaf-out. This treatment can be made during any time of the year, including winter months. For optimum control using this recommended method, apply the selective herbicide mix anytime from late winter to early spring.

For more information on the treatment of invasive plant species, industry success stories and best practices for effective vegetation management, visit

™ ® Trademarks of Dow AgroSciences, DuPont or Pioneer, and their affiliated companies or their respective owners. When treating areas in and around roadside or utility rights-of-way that are or will be grazed, hayed or planted to forage, important label precautions apply regarding harvesting hay from treated sites, using manure from animals grazing on treated areas or rotating the treated area to sensitive crops. See the product label for details. TerraVue is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. State restrictions on the sale and use of Garlon® 4 Ultra apply. Consult the label before purchase or use for full details. Always read and follow label directions.

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