Hi, I enjoyed your article on gardening under a tree. I've been searching over the past year and yours was most informative. My question: I've been using Clay Breaker for mulch as we have ridiculously hard clay here on the Eastern Shore of Maryland. And I like the look of it. Is it ok for use under my big oak tree? I have a White Oak and also a Pin Oak.
This is a Gypsum based product and is recommended you apply to lawns and garden beds and light dig in. You may want to use this to amend your clay soil, but it is not a mulch.
There are many types of mulch to use under trees.