Grazing Oklahoma: Honey Locust

The most distinguishing characteristic of the honey locust is the presence of large, reddish-brown thorns. (Photo courtesy of the Noble Research Institute)

By Mike Proctor, Noble Research Institute research associate / mdproctor@noble.org

Characteristics: Honey locust is a medium-sized, deciduous tree with pinnate leaves on older branches and bi-pinnate leaves on the younger stems. Its most distinguishing character is the presence of large, reddish-brown thorns. Thorns on the trunk and larger limbs often branch and may reach taller than eight inches or more in length. Thorns on smaller branches are stout and often two inches long or more. Flowering occurs in late spring. The flowers are subtle, with a strong, sweet odor, and can often be located by smell before they are seen. The tree fruit is a long, flat, slightly twisted, pod that grows up to 18 inches long.

Area of Importance: Honey locust was historically limited to the eastern half of Oklahoma, but extensive planting in shelter belts and elsewhere by early settlers greatly expanded its range to the west. Once restricted to bottomlands and streamsides by fire, honey locust is capable of growing on a variety of ecological sites and is one of the species contributing to the brush encroachment issue in the Southern Great Plains.

Honey locust seedlings are not shade-tolerant. If one is found growing within a closed canopy, it is likely evidence of a gap in the canopy when the tree was established. Honey locust will readily invade rangeland and does particularly well on clay sites. Trees mature and begin producing seed at around 10 years of age.

Attributes: Honey locust is a legume, but authorities disagree as to whether it fixes nitrogen. The fruit pods provide food for a variety of wildlife species including white-tail deer and northern bobwhite quail, and are consumed by livestock as well. Deer and livestock eat the young leaves and stems. The large, strong, branched thorns can easily puncture most tires. The wood can be used for a variety of purposes but has little commercial value due to low stand size.

Trees don’t develop large, complex spines for no reason. Spines are for defense against herbivores. However, herbivores that feed on honey locust today can easily avoid most of the spines. An animal with a bigger mouth might have a harder time dealing with them though. Ice Age mastadons and sloths might very well have been discouraged by those huge thorns.