Light

• Place Japanese maple bonsai trees near a window to receive indirect sunlight. During the summer it's important to protect them from direct sunlight to avoid scorching the leaves. Red leaves are more prone to sun-scorch than Japanese maples with green leaves. Red leaves may fade or turn green if given too little sun. Morning and late-day sun is ideal for bonsai trees.
  
  

Soil

• Japanese maples grow best in slightly acidic soil that drains well. Potting soil should contain organic matter such as chopped sphagnum moss or conifer bark. Adding chopped sphagnum moss is good for soil that may be more alkaline because sphagnum is slightly acidic and will help balance the soil pH.
  
  

Watering

• Water bonsai trees once a day in the early morning or late afternoon with rainwater, because tap water may contain elevated levels of alkaline. Maple bonsai are not drought tolerant and the soil needs to be kept moist. Do not over-water and make the soil soggy as this could cause root rot.
  
  

Fertilizing

• Maple bonsai trees should be fertilized with a high-nitrogen fertilizer every week to two weeks in the spring when the leaf buds open. In the late spring and summer, once the leaves are completely open, feed Japanese maples a well-balanced, diluted fertilizer. During slow growth in the hottest part of the summer, fertilize the bonsai once every two weeks. Begin using a nitrogen-free fertilizer in the late summer and early autumn, gradually reducing the fertilizer before winter begins. After re-potting or if the tree is weakened by disease, do not fertilize. Once there is new growth, fertilize lightly.
  
  

Pruning

• The branches and roots should be pruned at the same time so the roots of the bonsai don't become stressed. Prune branches of Japanese maple bonsai in the fall or winter to prevent the tree from losing sap. It's also easier to shape the tree with fewer leaves on it. For smaller leaves on bonsai trees, remove leaves from the tree, but leave the leaf stems, in early summer every other year. To retain shape of mature Japanese maple bonsai trees, pinch off the tips of new shoots after one or two pairs of leaves have completely formed.
  
  

Re-potting

• For trees under 10 years old, re-pot every year or two in early spring before leaf buds are open. Older trees can be re-potted every two to three years. A shallow pot is best, as it allows the roots of the bonsai room to spread out. Cut the roots back to half their length before putting them in a new pot.