There are four Elm trees planted together under this wooden box. Each tree branches out as it comes up an out side face of the box.
These branches are brought around and grafted to branches of the other trees or to the other tree on the other side. As the branches come up over the top of the box I try and lay the branches down on the top and get them to meet up in the middle and graft together as one tree.
What will happen is that eventually the plywood box will rot away leaving the hollow empty space with the box defined by the remaining trees and branches.