Honey Locust: Identification and Management by James M

Honey Locust: Identification and Management by James M. Locke NF-SO-11-01

Honey locust (Gleditisia triacanthos L.) is a native tree species also known as honey-shucks locust, sweet-locust, three-thorned acacia, sweet-bean or thorny locust. It has a natural range that extends from central Pennsylva- nia to South Dakota to southeastern Texas to Alabama. This range was probably expanded by Native Ameri- cans, who used the wood, pods and seeds for several purposes, and later by wildlife and ornamental plantings. It is best adapted to moist, bottom- land soils, but can survive on a wide variety of sites. Honey locust is often one of the first trees to occupy an area that was once woods, was cleared and is reverting back to woods. It is a moderately fast growing tree that has proven to be hardy and tolerant of drought conditions and saline soils. Identification The honey locust is a leguminous tree or a member of the Pea family (Fabaceae). At maturity, trees may be 70 to 80 feet tall and 2 to 3 feet in diameter at breast height, although under ideal conditions they may be up to 140 feet tall and 5 to 6 feet in diameter at breast height. The bark is medium to dark gray or brown with elongated plate-like patches separated by furrows. These plate-like patches may produce warty growths resulting in a rough trunk texture. Honey locust leaf arrangement is alternate, and its leaves are doubly4

Top photo: A mature honey locust tree growing on an upland site. Bottom photo: Bark pattern on a mature honey locust tree.

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compound, meaning each leaf is divided into leaflets and secondary leaflets. The secondary leaflets are 1 to 2 inches long with smooth mar- gins. Flowers are greenish-yellow and occur in small, numerous hanging clusters. Trees produce either pre- dominantly male or female flowers; however, some perfect flowers (male plus female) are usually present as well. The fruits are flattened pods 6 to 18 inches long that turn brown when mature. The pulp from these seed pods was used by Native Americans as a sweetener and is the source of several of the common names for honey locust. The most notorious feature of honey locust is the large thorns found on the branches and trunk. The thorns typically have one to three points, but may have more, especially those found on the trunk.

Management Considerations Honey locust management is highly dependent on the intended usage of a particular property. There are thornless cultivars that are commonly used for landscaping applications, but the naturally occurring trees are not suitable for landscaping due to the sharp thorns. The bean pods and leaves are utilized as a food source for white-tailed deer, sheep, goats, cattle, swine and many small mammals. It is also used as visual cover for many wildlife species while open pasture or range is reverting back to woods. Honey locust has been extensively utilized for windbreak plantings. These beneficial attributes Top photo: A doubly-compound honey locust leaf. must be tempered by the potential Bottom photo: Honey locust seed pods beginning to mature. for honey locust to become invasive and displace more desirable species. Honey locust is normally not a dominant species in naturally occur- growth capability and tendency to required in naturally existing climax ring forest stands. Due to its intoler- spread from the edges of wooded forest communities. However, when ance of shade, it tends to establish areas, it can rapidly develop into a allowed to establish as the dominant in openings of the forest canopy problem in range and pastureland. species, it will take many years to or on the edges. Due to its rapid Honey locust control is not usually develop normal species diversity.

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ing program, obtain all necessary training and become familiar with laws pertaining to prescribed burning in a specific locality. In the case of extremely hot fires that top-kill slower growing tree species, fires may create openings where the rapid es- tablishment and regrowth of honey locust may allow it to become the dominant species in the openings.

Mechanical methods Honey locust can be mechanically cut with a chainsaw, tree shear, hand loppers or other suitable tools. The trees should be cut as close to ground level as possible with the cut as flat as feasible to aid in a stump herbicide treatment soaking into the freshly cut wood. Honey locusts are known to resprout, so unless the stump is treated with an appropriate herbicide, it is likely to grow back. This regrowth is typically multistemmed and will be more difficult to control with herbicide than the original tree, due to the low foliage to root mass ratio. A very effective cut stump treatment is one part triclopyr (example: Remedy®) and three parts diesel or mineral oil. Apply to the sides of the freshly cut stump and outer portion of the cut surface, especially the cambium, in a manner which thoroughly wets the stem and root collar area, but not to the point of runoff. In order to be effective, the treatment must be applied to a fresh cut, preferably within an hour of cutting. If labor is avail- Top photo: Multi-pointed thorns on the trunk of a young honey locust tree. able, having one person cutting Bottom photo: Multi-stemmed honey locust re-sprout after brush-hogging. and another immediately stump treating is effective to help ensure Management Methods no stumps are missed and the Prescribed fire treatment is applied quickly. Due to its thin bark, honey locust is regular prescribed burning program To clear large, dense areas, easily top-killed by burning. Unfor- will often prevent honey locust from a bulldozer or track-hoe may tunately, it will readily resprout from developing into a significant problem. be used, but resprouting from the existing root mass. Maintaining a Prior to initiating a prescribed burn- secondary buds will occur.4

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Chemical control There are several herbicides la- to the mix when a broader slower than the rest of the tree and beled for honey locust control. spectrum of activity is desired. may continue to pose a problem. The following options have been For basal soil treatments, apply highly successful for many pro- undiluted Velpar L® with an exact Summary ducers in Oklahoma and Texas. delivery handgun applicator set to Honey locust is a native tree that For broadcast foliar treatments, 4 milliliters per trigger pull. A Velpar is a normal part of many Texas and apply 1 gallon of a picloram and Gun is available from Helena Chemi- Oklahoma landscapes. It can be a 2,4-D premix (example: Grazon cal Company that works well or positive or a negative component P+D®) per acre in sufficient volume something like an Ivomec® gun also depending on the goals for the to provide good coverage of the works. Apply 4 milliliters of undiluted property. Each manager must decide foliage. Use a surfactant at 0.25 to herbicide for each inch of trunk how honey locust fits into their goals 0.5% of the total mix volume. Apply diameter at breast height. If treating and how to best manage them. from late spring, after the leaves resprouts, base the number of 4-milli- Always read and follow label direc- are fully expanded and mature, liter applications on the diameter of tions. No discrimination is intended through fall. Do not apply during the original tree, not on the diameter and no endorsement is implied for periods of drought stress. Applica- of the resprout. If multiple 4-milliliter any specific products. References to tion time frames are usually late applications are required for each specific products or trade names are May through June and again in plant, space them evenly around the for educational purposes only. < September when early fall rains have trunk. Direct the treatment to the soil alleviated summer drought stress. within approximately 3 feet of the For high volume foliar treatment root collar. Apply from spring green- Literature Cited of individual plants, apply 0.925% of a up through early summer. Rainfall is Blair, R.M. 1990. Gleditsia triacanthos. Pages picloram and 2,4-D premix (example: required after application to move 358-364, in R.M. Burns and B.H. Honkala, Grazon P+D®) and 0.5% nonionic the herbicide into the root zone. Silvics of North America: Volume 2. Hard- surfactant. Spray to thoroughly wet Expect the grass to be dead for one woods. USDA Forest Service Agriculture foliage. Apply from late spring, after to two years in a 3- to 4-foot-diameter Handbook 654. Washington, D.C. the leaves are fully expanded and area around each application site. Nesom, G. 2003. Honey Locust Plant mature, through fall. Do not apply After honey locust trees have been Guide. USDA/NRCS National Plant Data during periods of drought stress. killed by herbicides, dispose of the Center & Biota of North America Pro- Application time frames are usually dead trees by bulldozing into piles gram. Chapel Hill, N.C. http://plants. late May through June and again in and burning or by burning in place. usda.gov/java/profile?symbol=GLTR. September when early fall rains have Be sure the trees are completely Shadow, R.A. 2008. Honey Locust alleviated summer drought stress. dead before disposal. When dead Plant Fact Sheet. USDA/NRCS East If the stand is mixed with bois trees are left standing, they will Texas Plant Materials Center. Na- d’arc, elms, oaks, etc., add 0.25% to eventually fall and decompose; cogdoches, TX. http://plants.usda. 0.5% triclopyr (example: Remedy®) however, the thorns decompose gov/java/profile?symbol=GLTR.

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