How Large A Cut Needs Sealant?
The instinct to seal a recent cut is reflexive. Selective application may speed up our work, however, and economize sealant.
In Bonsai Heresy I cover the arguments before and against cut sealants, on page 216. Although I cover the differences between bonsai and arborist techniques—and that both are right for their purposes—one thing I don’t touch on is cut size. The practical question is, “What cut is too small to bother with?”
Many conifer cuts, like pines and spruce, are not sealed at all. The resin is the sealant. Large wounds, such as the creation of shari on conifers, is an example where sealant is not used.
Deciduous trees are another matter. These may experience dieback without a sealant, if the cut is a large one. Small cuts—1/32” to 1/8”—will die back to a bud no matter what you do, and sealing those is wasteful and pointless. Typically we should cut above the bud on these thin twigs, don’t seal, and let it die back to the bud you wish to push.
A Styrax with two cuts. The cut to the right is 1/4” wide and received sealant. The cut above the bud is 1/16” wide and did not receive any.