Most varieties of Japanese maple are cold hardy down to minus 0 degrees F for the tree, but have much more sensitive root stocks that can only tolerate minus 14 degrees F. However, protecting the root stock from sudden, unexpected drops in temperature is generally a good idea. Japanese maples can be damaged by cold, drying winds in winter. Planning for this in location selection is the best protection, but wrapping your tree can help protect it during unusually cold wind storms.
Plant your tree in a location that is not susceptible to drying winter winds. If your tree is already in a location that gets direct winter winds, consider transplanting the tree to a more protected location.
Prune your maple with a pair of sharp pruning shears in late fall or early winter to reduce stress from cold and wind.
Mulch your maple with four to six inches of straw, dry leaves, or other mulch with a high air content. Mulch an area as wide as the reach of your tree's branches. For example, if your tree is six feet wide, mulch three feet on each side.
Protect your tree from expected wind storms by wrapping it in plastic sheeting. Although it's best to plant your tree in a protected location, temporary wrapping in plastic can prevent damage from unusually cold winds and storms.