Should I Shred My Leave Piles?

Q: I have a heavily wooded lot. I take the fallen leaves off my grass and move them into an area with mature oak trees. The piles are four feet high when I’m finished. Is it better to leave the leaves whole or shred them? 

A: I think the main question is whether the leaves mat down and prevent air and water exchange with the tree roots. Some leaves do this worse than others. A four-foot-deep pile doesn’t sound good but if it composts down to a thin layer after a few months I don’t think it would be harmful. I would experiment on a small area, putting a pile of whole leaves in one spot and mulched leaves in another and see what happens by summer’s end.