The Curious Case of the Honey Locust


With three-pronged thorns that can be up to 6 inches long, the honey locust (Gleditsia triacanthos) is one of the more ominous-looking trees of our area. However, if you look closely, these thorns are a curiosity. For starters, the thorns are only found on the trunk. Upon further inspection, they start growing about 5 feet from the base of the tree, but then stop about halfway up the trunk. Additionally, there seems to be no pattern in how the thorns grow — there are sometimes huge gaps between patches of thorns. Some clumps of thorns are bigger than others.

Honey locust tree

The thorns go too high on the trunk to deter deer. The spacing is too far apart to deter squirrels (they can just climb around or over the thorns). Why would a tree have these daggers just growing from the tree?

The answer revolves around an animal, but not an animal that can be found today. Scientists believe that the mastodon is the reason for the honey locust’s thorns.

Apparently, the deterrent is just right for mastodons, which explains why the thorns abruptly discontinue their growth. What’s even more curious is that the trees needed these beasts’ help.

15,000 years ago, when mastodons roamed this area, honey locusts would have been a good food source for mastodons. The sweet, but tough, seed pods would pass through the digestive system of the mastodons undigested. As the animals moved from place to place, they would “release” the seeds (with a little fertilizer) in new places.

So next time you see the curious honey locust, you can decide for yourself whether the honey locusts are missing their mighty mastodons.

Adam McCosham
Conservation and Parks Manager, Shawnee Lookout