Why are the leaves on my maple going crispy round the edges?
In spring this can be caused by light frost damage, often caused by the tree coming into leaf too early. You can often avoid this sort of damage by siting your maple away from too warm or sheltered position during winter, which can help prevent the plant from leafing out too early. Don't worry though - your plant will make a full recovery providing any stem damage is trimmed off.
In summer this can often be caused by water stress, either too much or too little. This problem only usually occurs in plants in containers or newly planted plants in the ground.
Too little water will cause some root damage, this will concentrate the sap around the edges of the leaves and as the plant cannot replace the moisture it is losing through the leaves so efficiently it reduces its leaf size by aborting the edges. Occasionally complete defoliation occurs. In an otherwise healthy plant it can make a full recovery and produce new foliage if it has time.
Too much water will damage or rot the sensitive roots, leaving the plant with a smaller root system unable to support its leaf canopy. However, by careful attention to water requirements in container grown plants you can ensure that this problem rarely occurs. Also, the older the plant becomes it is far more able to cope with erratic watering. Over watering should never a problem in a free draining container with free draining soil - which are the conditions that Japanese Maples thrive in.