Answer: Japanese maples grow best in morning sunshine and afternoon shade. If they get too much hot summer sunshine, the leaves can scorch. Some Japanese maples are more affected than others, and some outgrow this as their leaves mature. Wind burn can cause crispy leaves, but too much sunshine or too much nitrogen fertilizer will cause crispy leaf margins. Since the trees need the leaves for photosynthesis, I wouldn't prune them off unless they were completely dead. As unattractive as crispy leaf margins are, the rest of the leaf is busy producing carbohydrates for the roots of your tree. I would leave those leaves alone.
You may want to consider moving your tree this winter to a more protected spot - dappled afternoon shade; morning sun. Or you may want to wait and see if it outgrows the problem.
Mulch is any material that covers the soil to slow evaporation and suppress weeds. Mulch can be inorganic (gravel, for instance), or organic (compost, bark chips, bark nuggets, straw, etc.) There is no difference in the way inorganic and organic mulches work, except that organic mulches will eventually decompose and will need to be replaced. As they are decomposing, they are leaching minerals into the soil so from a soil's standpoint, organic mulches are the preferred mulch material.
Hope this answers all your questions!
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