[mdjlucan]

I damaged the bottom of the Plumtree with the strimmer Tar a lump of bark off three months ago how can I repair it

[mumofstig]

You can't - the wound may scar over successfully on its own.

[mdjlucan]

Can you put a bandage around it ?

[mumofstig]

If it's a big wound, it may have been worth applying a bandage when you did it, but IMO it is too late to make any difference now.

[ilan]

Whilst as said you cannot repair the damage providing it does not go all around the tree it will be ok. My oh has killed a few of our trees with the strimmer . So every one now has a grass free area  cut out and 4x 1 ft high stakes placed around them for protecton .

[Trikidiki]

Depending on how large the damaged area is it could be possible to  veneer graft a piece of bark from a branch that could be pruned out. Otherwise you could bridge graft over the damaged area using some pieces of a small branch. There are lots of descriptions of how to do both on the internet.  If it is going to die if you do nothing then you have nothing to lose. If it works you can give yourself a pat on the back.