Maybe some of the older fellas here have heard of this? My great grandfather used to always say that when you plant an oak tree to put crawfish shells in the hole. He said it would keep the roots from growin above the ground. He claimed to have done this when he planted his oak trees and he made my dad do it when he planted his.
He's been gone for years now, but I thought about it this weekend when I was cutting my dad's grass for him. My oak trees have tons of roots above ground that I have to weedeat around and his doesn't have a one. I walked over to my great grandpa's old house and sure enough. Not a one root above the ground. The one oak tree that my grandpa did plant on his property doesn't have any, but the ones that were already on the property do. My other grandparent's back yard is covered in roots, as it my aunt's.
Thinking about it now it's kind of cool. Could just be a coincidence though. Anybody ever heard of this old trick?