Introduced to the West in 1820, Japanese maples (Acer palmatum) have since proven to be one of the most versatile small trees in the landscape: they can be planted in groups, or grown as single specimens or accent plants, and are even popular subjects for bonsai.
Most of the varieties available at nurseries today are the culmination of hundreds of years of breeding and selection, and widely vary in form (from upright or rounded to weeping), leaf colour (purple, crimson, gold, green and variegated) and leaf shape (from finely serrated margins to deeply dissected lobes).
Late autumn through to late winter is the best time to prune a Japanese maple, while the tree is leafless and dormant; it’s also easier to see the woody parts of the plant since they’re not obscured by the leaves. Never prune a maple in early spring when the sap is rising and the tree’s energy is focused on producing fresh foliage. Minor corrective pruning and thinning may be done in the summer when the tree is in active growth.
The aim is to accentuate and emphasize the Japanese maple’s own natural shape, so it’s important to observe its growth pattern before making any cuts. Ensure your pruners are razor-sharp for clean cuts (ragged edges are slow to heal and can harbour disease). Sterilize pruners in a solution of nine parts water to one part bleach before you start; re-sterilize between trees if you’re pruning more than one specimen to avoid transferring pathogens.