Black walnuts are a very common tree up here in the mountains. My backyard is almost completely covered with the walnuts every fall. I’ve been woken up very suddenly more than once in the middle of the night from them dropping on my roof. Black walnut trees are pretty interesting plants with some unique properties and uses. Let’s talk about black walnuts and what some of those properties and uses are.
Black walnuts are in the walnut family which includes pecans and hickory trees. It can be identified by its leaves and bark. The leaves are alternate, pinnately compound. That means the leaves alternate from one side of the branch to the other in a kind of palm tree leaf shape. The bark has deep ridges in it that come together and separate going up the trunk. The nut has a green husk on it that turns to a brownish black color after falling to the ground.
Black walnut trees can grow to be 100 feet tall with a canopy spreading up to 75 feet. The trunks can grow up to 7 feet in diameter. Black walnuts are difficult to transplant because they have a deep taproot, making it difficult to pot them without cutting the roots. They like moist well drained soils. This makes them make good trees to grow along stream banks.
An interesting property of black walnuts is that they produce a chemical called juglone. Black walnuts put this chemical out through the roots and into the surrounding soil. Juglone will stop the growth of or kill some types of neighboring plants. It’s like a natural herbicide that the tree uses to reduce competition with other plants.
Economically speaking black walnut trees can have dual value. The walnuts can be harvested and eaten. The actual nut which is edible is protected beneath the husk and a shell, making it difficult to get to. From personal experience I will say if you are peeling the husk off by hand to wear gloves! The husks will stain your hands. I used just about every product I could find from gasoline to quaternary ammonia to dish soap and the stain stayed on my hands until the skin that was stained wore off. Besides the nuts, the other value of black walnuts is from the timber. A single tree can be worth up to $20,000. That price tag is only if the tree is of the highest quality. Unfortunately for opportunistic black walnut owners in Georgia we don’t have the right climatic conditions to grow high quality black walnut timber. Water stress and cold winter temperatures that we don’t get, but that occur in places like Iowa, lead to better quality. When European settlers arrived in Georgia they also cut down many of the high quality black walnut trees leaving behind short and scraggly trees that aren’t as good for timber, and we see the descendants of those trees today.
It’s also possible to make syrup from black walnut trees. Black walnuts don’t produce as much syrup as maple trees do, and the flavor is a little different. The flavor has butterscotch and nutty overtones. One thing to be aware of before you begin making your own syrup is that people with nut allergies can be affected by walnut syrup too. The ideal time to tap trees is when you have cold nights with day temperatures in the 40s.
If you have questions about Black walnuts or other trees please contact your local Extension Office or send me and email at Jacob.Williams@uga.edu.