Bridge graft

A bridge graft is a grafting technique used to re-establish the supply of nutrients to the rootstock of a woody perennial when the full thickness of the bark has been removed from part of the trunk.

Damage to the innermost layer of the bark, called the phloem, can interrupt the transport of leave photosynthesised sugars down to the roots. Such wounds are often caused by rabbits or other rodents, stripping the bark away and girdling the tree. The inability to transport sugars from leaves down to the root system causes the root death after the stored nutrient are exhausted, which eventually results in the plant's death.

A bridge graft uses scions to 'bridge' the gap. Each scion is taper cut in order to accommodate the need for matching the cambium layers of the scion with those of the tree to which it is being grafted. It is also vital that the scions be placed so that the end which was closest to their own roots before they were cut is at the bottom of the graft, and the end which was closest to the growing tip is at the top. Incorrect placement (cells in the scion being upside down) will result in its death. Once in place, the graft wounds must be completely sealed, in order to facilitate joining together and prevent infection of the site.

Where one-quarter or less of the trunk circumference has been girdled, it may not be necessary to use this technique. It is also difficult to apply on small caliper tree trunks.