Is it small? Most trees do require it's crown to be exposed to sunlight in order to begin regrowth... It might be wise to start removing those hardcovers now but leave the bottom mulch on until May when frost danger is gone. The grounds are warming up but there's still ice beneath the ground - until complete warming and because of the erratic temperatures in March thru April, it's important to keep the ground temperature around the roots as steady as possible and this is accomplished by keeping the mulch on. Around May - start removing the mulch from it's base.

Normally I would suggest using burlap to protect the crown and this is simply to prevent branches being broken from the weight of accumulating snow. Burlap allows filtered sunlight to penetrate it and thus allow the plant to bud and grow. However if snow accumalation had been tremendous enough, plywood may be necessary.

ianna

Just outside Ottawa, we bought our Japanese Maple from Rideau Woodland Ramble. They say that the worst problem for these trees is drying winter winds - and so recommend enclosing in a tepee made of strong sticks and a material which is sold at Canadian Tire and looks like white felt. We put up the sticks and staple the white stuff on in about 10 minutes flat. Our Japanese maple has now survived 3 winters and is doing fine.