I have a 100 year old plus, sweet gum tree that has a place where a very large limb had been sawed of flush wth the tree years ago. This spot is about 18" X 18" and 12" deep with the rotten wood removed.

I have cleaned all the dead wood etc.out of hole, sprayed it good with 3M Rubberized Auto undercoating and am letting it dry good.

I am trying to decide what to do next. I see that a lot of you suggest fillib the hole with Rocktite or Mortar etc.

My question is, is it better to fill the hole and cove it with a metal covering, or just cover/seal the hole and not fill it.

I would appreciate your answers and if you suggest filling it, what is the BEST MATERIAL FOR FILLING THE HOLE OF A TREE.

Thank you
jerryd14

Hi! jerryd14, welcome to AMHD :)

Borrowed from http://www.utextension.utk.edu/publications/spfiles/SP683.pdf It's at the bottom right of page 2
Cavity Filling
Filling of large holes or hollows in the tree is generally
done for cosmetic reasons. There is little data to indicate
that a filled tree has better mechanical stability. However,
fillings may give the callus tissue a place to seat, thus
stopping the in-roll (folding) of the callus (Shigo 1992).
Almost any filling can be used as long as it does not abrade
the inside of the tree.
The filling of a tree cavity is generally expensive
and not recommended. The filling does not stop decay and
often during the cleaning of the cavity, the boundary that
separates the sound wood or the callus growth from the
decayed wood is ruptured. Thus, this cleaning for cavity
filling can have more detrimental effects on the tree than
if it were left alone. Care must be taken not to damage the
new callus tissue that has formed in response to the tree
damage and subsequent decay.

I feel this pretty much sums it up.
If done right it's helpful, if not your only hurting the tree more.

This is the site I generally use: The University of Tennessee Extension. Forestry, Trees & Timber (http://www.utextension.utk.edu/publications/forestry/) You will find the Cavity Filling link in Maintaining and Protecting, third one down.

Some good reading on trees by Dr. Alex Shigo
http://www.osun.org/Alex+Shigo-pdf.html

K