Pruning and Planting:
Pruning for form is best done late summer when the weather is dry to avoid inviting diseases. Working up and from inside to out, clean away small twigs growing along the trunk and major branches, remove any dead wood and take away crossed and rubbing branches. Make clean cuts where branches join the trunk or stems join a branch. Stubs invite disease and are also unattractive. Stand back and look carefully at your tree’s shape. If it is not pleasing, look for what you need to remove to improve its form. Before making each cut, study the branch’s path and visualize the tree without it. For the tree’s protection – do not prune unnecessarily. Planting is best done in the fall because the roots get a chance to become established and come spring the tree will be ready to put on new growth. Chooses a well-drained site to prevent root rot diseases. If there is no rain in the fall be sure to water until the steady fall rains come and again in the early spring if there is dry weather. Mulching is always a good idea for fall. It will help insulate the roots for winter and protect the early spring root growth. Mulch the root area with about 3 inches of bark, keeping it a few inches away from the trunk to avoid rotting.
Summer heat and drought problems: Mulch your tree with 3 inches of fine bark mulch (not cedar bark) to insulate the roots and preserve the moisture in the earth. Water deeply twice a week; water more often if it is a newly planted tree or a container-grown tree. Leaf tip burn is unsightly, but not a cause for panic. Because Japanese maples have thin delicate leaves, a drying, hot afternoon breeze can take moisture easily away at a rate faster than the root system is able to replenish them. Afternoon shade and good watering practices help, but in extreme conditions you may have to live with it.
Under extremely stressful conditions your tree may drop all its leaves. Do not despair. It is protecting itself while telling you it is not getting enough water and humidity. When your maple is drought stressed do not fertilize it until it is looking better. Also, while your tree is stressed, be on the lookout for other problems such as insects or disease so you can deal with them immediately and prevent a spiral of decline.
Disease Problems: Disease attacks and kills trees that are weakend repeatedly by drought or water logging. The control for disease is to create the best possible growing environment. Anthracnose, a fungus, causes deformed leaves with chunks missing from the edges and large brown-through-to-white blotches; twigs and shoot tips may die back. Treatment with a copper spray is recommended. A more serious disease is a soil-born fungus, verticillium wilt. Leaves wilt or die suddenly and established trees that contract the wilt may lose branches over several years before succumbing or may look normal in the fall but not flush out in the spring. It’s good cultural practice to rake up and destroy fallen leaves of any diseased tree. Japanese maple leaves may show signs of browning or spotting when chemical sprays or chemical nutrients are used heavily. Organic methods of pest control and the organic fertilizers are less harsh.
Winter Care of Your Japanese Maples:
After a severe winter many people find branches snapped out of their dwarf, weeping maples. This may happen because the branch tips freeze to the ground. When they do, the flexibility is lost and the burden of heavy snow on the top can cause branches to crack or even break. It is a good idea to gently remove snow accumulation from the tops as soon as possible. At the same time, be cautious about a lot of ice; whole branches may break, the tips may snap off and the bark may be badly damaged. To minimize the damage of winter hazards, remove dead leaves that cling to the ends of branches before snow or ice arrives.