Answer: Japanese maples will grow in full to part sun. They prefer afternoon shade if your summer weather gets hot. After planting your Japanese maple, mulch with 2 1/2 - 3" of shredded bark, preferably hardwood, to insulate the roots and prevent water from evaporating too quickly.
Water deeply twice a week; water more often if it is a newly planted tree or a container-grown tree.
Pruning for form is best done in late summer or early fall. Good form is largely a question of personal taste. We like to let air and light into the center of the tree so that we can see the tracings of branch structure. Working up from the base and from inside to out, clean out small twigs growing along the trunk and major branches, dead wood, and crossed and rubbing branches. 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 where the branch goes and visualize the tree without it. Cut just above a live bud or just in front of the collar (the small ridge where a branch attaches to another).
Planting in the fall can be very rewarding. Try to plant at least 4 to 6 weeks before the ground freezes. The roots get a chance to establish themselves, and, come spring, the tree will be ready to put on new growth. If there is no rain be sure to water until the ground freezes and in the early spring.
Mulching is always a good idea for fall; it will help insulate the roots for winter and protect their early spring growth.
Winter care of your Japanese Maples:
Make sure your trees are well watered in the late fall and up till the time when the ground freezes. Mulch with about 3" of shredded hard bark, keeping it a few inches away from the trunk to allow air to circulate.
Japanese Maples are extremely vulnerable in spring. They leaf out of winter dormancy with the first warm weather. 'Katsura' and 'Ueno yama' are among the first. Tender new growth is then at the mercy of a late spring frost. If your tree is young and small enough, protect it from these frosts by covering it. It is the frost more than the cold that is the danger; a good wind can save the day.
Damp, hot springs can be equally dangerous due to the fungal problems they bring such as Botrytis, Pseudomonas and Fusarium. Good air circulation, soil drainage and sanitation practices all help prevent these problems.
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