There is a mature black walnut tree next to my property. It is a mess - nuts fall all over, stain my new brick paving, poison my grass and flowers. I have spent thousands on flowers and plants to find they seldom survive. It is my understanding that the tree is the culprit. Everyday I come home to find another load of nuts and hulls dumped on my lawn, and chewed up fragments from the squirrels. I need to minimize this tree's effect on my landscape. I need to sterilize it. How do I do this?
Black Walnut Tree
Certified GKH Gardening Expert
About the only thing you can do is get rid of the tree. Once the tree is cut down, most of its adverse effects will be gone in a year or so. Black walnut leaves and fruit have most of the alleopathic chemicals and since those will not fall (because the tree is gone), it is greatly reduced in the area. The roots do have some alleopathic chemicals, but taking steps to kill the stump for good, by using Roundup or other methods, will help to stop the tree roots from producing more, but there is still some there while they decay. A great way around this is to use raised beds in the area. Since the leaves and fruit will not fall on the beds anymore, the soil used in the beds will not have the alleopathic chemicals and the soil will be above where the residual chemicals from the roots still are.
Alternatively, if you do not wish to remove the tree, you could try planting compatible plants within the landscape. This article will help: https://www.gardeningknowhow.com/edible/nut-trees/black-walnut/black-walnut-compatible-plants.htm