In cases where the bark has been damaged but some or all of the cambium and phloem remains, the tree may make a natural recovery. If in doubt, however, attempt repair.
Repair the damage whist still fresh for the best results. Retain as much of the remaining bark as possible to help the movement of sap and encourage healing.
Partially girdled trees
Step 1: Pare the rough edges away with a sharp knife.
Step 2: Cover the area with a 4cm deep layer of damp moss.
Step 3: Wrap with polythene and hold in place with waterproof adhesive tape. The polythene should be wide enough to completely cover the area and prevent the moss drying out.
Step 4: Leave the patch in place until the end of the growing season i.e. at least three to four months to allow the damaged to heal.
Step 5: Check the ties periodically to ensure there is no serious constriction to the trunk and loosened if necessary.
Step 6: Ensure adequate soil moisture by watering during hot, dry periods in spring and summer.
Completely girdled trees
Initially the moss and polythene can be applied as for partially-girdled trees but if all or nearly all the bark is gone some form of grafting will be necessary. Grafting is normally carried out in spring when the cambium is particularly active and the bark is "lifting" easily.
There are two methods of repairing a girdled tree:
- Bridge grafting – this involves bridging the damaged section with scion material (i.e. bark/wood taken from the same species or cultivar of tree, not the rootstock). For small trees this is done by using a side graft. For larger trees an inverted L rind graft is used.
- Inarching or Approach grafting – a vigorous rootstock is planted alongside the damaged tree and eventually takes over the function of the original roots.
For full and illustrated descriptions of the above grafts, please refer to The Grafter’s Handbook by R J Garner (revised and updated edition 2013) ISBN: 9781845337544 and in particular Chapter VIII Grafting established trees, section “To repair and improve”. There are also resources available online.