All those fallen walnuts can be quite an annoyance. Photo: thehorse.com
Question: What product could I use to treat my black walnut to prevent it from producing nuts? The nuts really upset my neighbor. It’s a magnificent tree, 60 feet (18 m) tall, but nuts are unwanted.
Jean Lafontaine
Answer: This is not something most gardeners would consider doing, but it turns out it is quite possible.
There are plant hormone products that can prevent trees from producing fruit (and nuts are fruit). These products, like Florel Growth Regulator (active ingredient: ethephon) and Fruitone N or App-L-Set (naphthalene acetic acid or NAA), essentially overdose flowers with hormones and can therefore cause the fruit to abort. They’re mostly used in orchards to control fruit production, but can be used in the home garden.
None of these products is specifically recommended for walnut trees, but they are known to work on a wide variety of trees, from apples to willows and horse chestnuts and so you’ll probably need to experiment a bit. Usually, they need to be applied around the middle or the end of the flowering period or sometimes just as the fruits start to form. An application at the wrong time may have no effect or may even stimulate increased fruit production. So, for the first year, you may have to limit your treatment to individual branches to find out at what point the product is the most effective on walnut trees.
Also, be aware that these products can disrupt the growth of the tree, causing, for example, changes in its branching. Again, you have to try them out to see.
You’ll have to cover yourself with protective clothing from head to toe and keep other people and pets away from the area during treatment. It may be necessary to cover other fruit trees in the area with a tarp while spraying. And it will take a powerful sprayer to reach all the branches of a 60-foot (18-m) walnut tree!
Unless there are a lot of orchards in your area, in which case you might find one of these products in a local agricultural store, you’ll probably have to order these plant hormones online.
But…
That’s a lot of effort to keep a neighbor happy. Have you ever considered offering to go pick up the nuts that fall on their property instead? With a nut gatherer, it’s easy to quickly harvest nuts from the ground.
Or, if no compromise seems possible, it might be wiser to cut the tree down. Then you could plant another tree … well away from the property line. When a tree is in the wrong place, removal is often the only logical solution.