Repair a Cracked Black Willow Branch
A cracked branch in a favorite black willow shade tree needs to be investigated fully. Typical causes could be very high winds or heavy snow falls. A crack in an apparently healthy tree could be a sign that all is not well. A repair should only be attempted in a substantial branch, at least three inches in diameter.
Step 1 – Secure the Branch
To prevent any further damage while you check the cause, prop the branch securely. Try to prevent movement.
Step 2 – Check the Crack
Examine the crack carefully. If it is a stress crack there will be clean wood showing under the bark and no evidence of rot or beetle infestation. Inspect all the branches for similar damage or indications that such damage might occur.
Step 3 – Possible Self Repair
If there are no other cracks and no indications of causes other than accident or stress, consider bracing the branch. If you have spotted the crack very quickly there is a chance that the tree can repair itself.
Step 4 – Try to Close the Crack
While you watch what happens to the crack have someone manipulate the branch. If the crack is along the top side of the branch, have them raise the end of the branch – hopefully the crack will close.
Step 5 – Bolt the Crack Closed
Prop the branch so that the crack is closed and then drill holes for 4 quarter inch coach bolts. Using large washers, tighten the bolts to hold the crack as firmly as possible. This is a basic tree repair but effective. As long as the cambium layer of the tree immediately below the bark is not damaged, a new layer of growth will be completed to help cover the crack.
Step 6 – Make the Props More Permanent
It will take the branch a long time, at least two years, before it will be able to safely support its own weight. Until that time the props must be made secure. If only a single point of support is necessary you can make a tripod that will be very stable and still allow a degree of movement in the shade tree.
Step 7 – Lighten the Load
Without spoiling the looks of the sick tree too much, try a little tree pruning to thin out the growth on the branch. This will help create less pressure on the support points.
Step 8 – Seal the Crack
To keep water and insects out of the crack you should seal it with pitch or a special wax from a tree surgeon.
It is important to remember that a tree branch will never heal itself fully as a broken bone will. There will always be a weakness at the point you have made the repair. The coach bolts should prevent the crack from spreading along the branch. Sometimes the safest cure is to cut the damaged branch out.