Allelopathic American Elm
Just found out. My garden is riddled with American Elm roots and also Pecan but not Walnut. I do have a section I can move the garden to but I was sorely hoping to utilize the entire place over time and also to utilize some of the dappled shade during the heat wave.
At present my plans are to beef up the entire garden bed by composting directly on top and leaving 4-5 inches of compost to be utilized as the planting bed.
Perhaps I should make it even more dense placing cardboard - a slower type of composting material - at the very bottom of my bed as far as I can dig?
I do remove roots when I come across them but some of these are very large and immobile, of course. The canopy of this elm tree has about a 30' radius. The garden bed is positioned on only one side of the tree, of course.
(Dawn, this might be why my tomato plants seems "wimpy" when I planted them. They still are. Otherwise, they were OK. They are, indeed, stunted in growth which could be a number of things for which I am clueless.)