Tomatoes or Walnuts?

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It’s a tough choice to have to make. As southerners, we hold our tomato plants in high esteem and go to great lengths to have the biggest and best plants around. But, then again we also think highly of banana nut bread and black walnut pound cakes too. Why do we have to make a choice? Well, for one thing, life is tough and there will always be choices out there that have to be made. But, in this case it is because of a disease called walnut wilt. It isn’t really a disease-it’s more matter of being in the wrong place at the wrong time!

Black walnut trees give off a toxin through their leaves, nuts and roots. This toxin is called juglone and is used by the tree to kill off other plants that might be competing for water and nutrients. Consider it a self-preservation tactic: kill or be killed. This phenomenon is called allelopathy. Other trees such as certain maples and oaks also produce these toxins but none to the extent of the black walnut.

Tomatoes might grow successfully in the vicinity of a black walnut tree for a while but as the tree grows, so do its roots and eventually the roots will reach the garden. Tree roots can stretch out many feet past the drip line of the tree. Symptoms of walnut wilt are sudden and dramatic. One day, a plant with nice, green tomatoes is beautiful and healthy. The next day it is severely wilted and within a few days it’s dead. Once the disease has affected a plant there is no remedy. Growing in raised beds can help for a while as long as soil is brought in from another location. But, eventually this soil is affected also. Even though tomatoes are the best know victims of walnut wilt, other plants such as potatoes, asparagus, azaleas, blueberries and rhododendron along with many others can be injured when grown in the vicinity of the black walnut tree.

Getting rid of the walnut tree is the only solution but even that solution is not a quick one. After the tree is gone, roots in the soil will continue to give off juglone for at least two years. Eventually, tomatoes will happily grow in the garden again but until then, if you have walnut trees you’ll sadly have to buy your tomatoes from the store. It’s one of those tough choices that gardeners have to make.