Black Walnut toxins in soil
I am hoping that someone could help me with a dilemma that I have. We moved into our house 2 years and 4 months ago. We have had two summers here. I started a garden the first year that we moved in. Our garden is about 35x55 feet. I am having problems with my tomatoes. It seems that we put in the garden a little too close to a row of black walnut trees. I had never heard of black walnut wilt before I moved here but sadly that seems to be what has affected most of my tomato plants for the past two years. The garden is about 25 feet away from the walnut trees. We are going to be chopping down these trees and planting maples over the summer, hopefully. I have researched and found that it will take about 3 years for the bad toxins (I forgot what they are called) are out of the soil. So we are wondering what to do in the meantime. My husband is thinking that we should bring in a lot of topsoil to put on the top of our garden now and then plant in that. I'm thinking that if we do that, we will still have a problem with the black walnut toxins leaching into the tomato roots. He seems to think we might get a few years of good soil if we do that. I don't agree. I think the toxins can leach in quickly, maybe giving us one year if we are lucky. Please advise us on this! I just don't know what to do about this problem!
Black walnut gives off a chemical called juglone which can inhibit growth of a number of different plants. Tomatoes are very susceptible to walnut toxicity. As long as there are pieces of walnut root in the soil, there is potential for juglone to still be in the soil. It is not likely that the chemical would migrate upward, unless you have actively growing roots moving in that direction. Unless you put a barrier between the raised bed soil and the old garden soil, the tomato roots could go deep enough to be affected by the juglone still in the soil. The raised bed would also need to have a good depth to accommodate the roots of the tomato plant. A good article to help you is from MSU: http://msue.anr.msu.edu/news/growing_vegetable_gardens_near_black_walnut_trees