When mulching around your maple trees you need to be aware of the graft site on your tree's trunk. Japanese maple trees are often grafted for easy propagation. The top tree part is called a scion and it is attached to a root. Your mulch, or soil, should never reach the grafting site on your Japanese maple tree trunk, otherwise, your scion might start growing roots of its own, which would negate the benefits of the original graft. Make sure to keep the soil level at the same height as it was orig