I cut a large weeping Willow tree down about two years ago from my backyard. The stump sat for two years and was a backdrop for many a branch/brush fire until finally I had the stump professionally ground down to woodchip. I know have approx 4 cu yards of willow mulch. My question is can I use them without fear of regeneration and/or is the acidity of the woodchips possibly to strong for the garden? I have cut a lot of big trees but was surprised at the amount and size of some of the larger roots.