If pines are considered to be the kings of bonsai, then surely the glorious maples must be the queens. I grow all types of maples in all sorts of styles, and achieve deep and detailed ramifications using reasonably simple techniques.
The species that are easiest to work on are the green-leaved types, such as the pure Japanese maple (Acer palmatum). The Yatsubusa varieties are more delicate, and I suggest that you do not leaf-prune these types unless you are sure that they can take it. Varieties such as Acer palmatum atropurpurem are sometimes weak and difficult to back-bud. Do not leaf-prune the deep-red to purple colour group. You can develop this variety through bud-pinching.
Kiyohime are by nature very dense, but as they are stronger at the sides keep the side growth down or the upper position will die back, leaving you with a bald tree. All maples will leaf-burn if you put them out into the windy weather of spring, so you should wait until the soft leaf becomes firm and hard. Keep them in a sheltered area away from wind, if possible.
The maple’s year.
- Early spring: Although you can repot at any time, this is the optimum period for the majority of maples. Kashima and Kiyohime will have started to spread at this time, so make sure they are protected. Feed 0-10-10 (zero nitrogen) every seven days to stop lush growth, but only after the buds have opened.
- Throughout spring: Start plucking out the bud centres.
- Early summer: After the first two feeds, start giving them high nitrogen feed to start building up stamina in young trees. If you want good autumn colour; cut down the high-nitrogen food. If the tree is healthy consider a full or partial defoliation, which can be followed by selective wiring. The tree should be looked after as during spring. The problem with summer defoliation is sunburn rather than winds.
- Midsummer: Wire trees with cage (not tight) or protected wire, and carry out major pruning at this time of summer dormancy. Reduce feeding until or late midsummer.
- Late summer: Start feeding weekly with low-nitrogen food. This is the last opportunity for defoliation before autumn.
- Early autumn: Trim any leaves that are growing out of the planned shape. Stop feeding if the leaves start to change colour. Good autumnal colour is achieved with with little or no nitrogen feed. The question is whether or not you want to risk the trees health for a short-term benefit. It is probably better to wait until the tree has been completed and then reduce the feed to zero-nitrogen for one year.
- Mid-autumn: Complete the feeding programme with low or zero-nitrogen feed.
- Late autumn\early winter: Remove any dead leaves and make sure the trees are protected against winter frosts and wind.
- Winter: This is the other time when you can perform major surgery on your maple bonsai.