I had black walnut trees in my backyard and learned the hard way that my garden would not grow because of the soil. This year I am making raised beds but I am wondering if I should have a medium between my ground and my raised bed mix, likes rocks or something else to prevent my ground soil from being soaked up. Or is their a height my bed mix needs to be to prevent that. Help please!!!! I miss having a garden immensely
Kent County Michigan
The danger is not from the juglone being transported upwards. It is from root from the trees entering your raised beds and growing up (the soil will be very nice for them)
Roots of walnuts can extend 3 to 4 times wider than the radius of the crown.(the distance between the trunk and the dripline of the tree).
Please read this article from MSU:
Growing vegetable gardens near walnut trees msu.edu.
You will see that they recommend a strong barrier at the bottom of the beds.
Another university sponsored article that I read suggested very strong plastic or a weed barrier. Weed barriers could be easily penetrated by a stong tree root, I think.
The problem with thick plastic is drainage.
The MSU article suggested wood, concrete or stone. If there are small gaps between the wood, a few inches of stone or perhaps some concrete retangular pavers placed close together but with room for water drainage, one of these may work.
Also note the vegetables which are not affected by juglone. Tomatoes can be grown in large pots..... be sure you get a variety that is good for this.