Should We Seal a Crack in Our Tree?
Q: "We have an old tree that has a crack in the bark. Is there something we can fill the hole with so that the tree doesn't rot?"
We have an old oak tree that has a crack in the bark near its base. Bees have lived in it, as have chipmunks, and now birds are nesting there. Once the birds leave, is there something we can fill the hole with so that the tree doesn't rot?
—Pat and Dan Plewa, Thorp, Wis.
Roger Cook replies: Before you do any work to this tree, have a certified arborist inspect it to see if it is structurally sound. It might be that it would be better—and safer—to remove the tree rather than patch the hole.
If the tree is in sturdy condition, you can keep the critters out by covering the hole with hardware cloth—¼- or ½-inch galvanized screen. When I'm concerned about moisture getting in, sometimes I'll nail sheet metal over the hole and paint the metal to help it blend in.
Whatever you do, don't fill the hole with concrete. It cracks and breaks off, it holds moisture—which encourages rot—and it does a number on chain-saw blades when the time comes to take the tree down.