Hi Christina; I have several allotments and one has ash trees along one boundary. 2 years ago I had a major exercise to remove roots and cut back as much top growth as I could. This year I found extensive regrowth of the roots, even beyond the spread of the branches. Dry conditions have excaserbated the problem so; because the trees are protected under local rules, I have reluctantly grassed over the affected area.
Cheers
Pete