Q:

How do I treat a wound where a branch broke off my apple tree?

One of the secondary branches on my apple tree broke just where it joins the main branch:

The branch is now hanging by just a little strip of wood and bark:
Click any photo for full size

I understand that the wound can't be repaired and that I should remove the broken branch. If possible, I want to do that in a way that preserves the rest of the main branch (it's the biggest one on the tree, and will be even with this part missing).

Exactly where should I cut the broken branch? At the wound site or a little further down the branch?
How do I treat the wound on the main branch to prevent diseases or infections from getting a foothold?

A:

In the end you want the wound to approximately follow the plane of where the branch split from the tree. You don't want to have a split or a shelf that would collect water as it will lead to rot.
I would begin by cutting upward with a saw to finish severing the branch. Let us say the broken branch and tree trunk form an inverted 'V' - cut upward through the apex of the 'V'. Take the branch away.
With the branch out of the way, I often find it easier to cut upward again from below any split, attempting to remove any split wood, cutting a surface that intersects the top of the split (shown in the photos). You will have to analyze your situation and apply your saw appropriately to remove the split wood on the trunk.
Once you've fashioned this into a surface that won't retain water (the rough split surface shown is fine as is), leave it be. DO NOT PAINT ANYTHING ON IT. Trees compartmentalize damage and as far as this wound is concerned, your tree will be just fine. Sealers either have no effect or encase pathogens that would otherwise have not affected the tree.

