I live in the high desert country of Northern Arizona where we have very few trees. I have several large Siberian elms which I desperately want to keep for shade. (It gets quite hot here.) There is about a 6 foot circle around the base of each tree where absolutely NOTHING will grow, and I've tried just about everything. Any ideas as to what my be causing this problem and what I could do to fix this problem?
Root competition from the trees - they hog all the water that lands there with a dense mat of roots that stops anything else penetrating.