Passing on here a study of wound closure from the 1970’s by one of the great arboriculturists, Alex Shigo. I wish to thank local arborist Rick Till for bringing it to my attention.
Alex Shigo
Shigo applied both clear and black plastic wraps—with no wraps as the control—around wounds. He concluded that black plastic wrap closed wounds faster than clear wrap, although clear was more effective than leaving it unwrapped. Also of note, much less decay was noticed in wrapped wounds than unwrapped, and here again black plastic outperformed clear. The study was done with large wounds.
We have some clever liquid and putty wound sealants that appear to stimulate wound closure on hard to close plants, like shrubs. But this old study is worth passing on, as an option.
Wraps for wounds have been used in bonsai—I’ve used them myself—but it’s nice to have supporting data. In the past I’ve tried green plastic nursery tape and seen good closure.
Shigo’s full study, co-authored by Walter Shortle:
Effect of Plastic Wrap on Wound Closure, Shortle and Shigo 1978
For further reading about a tree’s physiologic response to wounding, Rick recommends The CODIT Principle, by Dirk Dujesiefken and Walter Liese.