Pruning Japanese maples
Japanese maples can be lightly tip-pruned during the summer months to control new growth or runaway water shoots, but save the major pruning for December or January, when the tree is fully dormant. Do not prune later than February (or when the leaf buds start swelling), because the tree can bleed quite severely and become weakened.
All Japanese maples have “eyes” on the branches, where the leaves were attached during the growing season. These “eyes” are small half moon swellings, spaced every 1-3″ along the branches. Each “eye” faces a different direction, rotating along the branches.
Pruning 1/4″ above a particular eye will make the tree branch out in that direction the following year. You can control the shape and direction of the tree each year simply by deciding which eyes to prune above.
Avoid pruning beyond the previous year’s cuts. Always allow at least 2 “eyes” of new growth each year to remain on the tree. Pruning more severely can lead to knurled and stunted growth, with many tiny shoots coming out from the same spot. If a large branch needs to be pruned to thin out the tree and allow more light, prune it completely off. Make sure to seal all cuts larger than 1/2″ in diameter with a pruning sealer.