I'll leave you to your own designs for overwintering ideas. There's been much written about it on the forum.

If heat gain is your goal to help protect roots, clear plastic would be far more effective than black, but I'm afraid that you'd be apt to raise soil temps high enough to stimulate growth. This would produce new growth that freezes easily and goes a long way toward destroying cold-hardiness in the entire plant. Also, plastic is a mulch and is as good at holding moisture in as it is at keeping it out.

Good luck to you.

Al

Buy a bag of mulch at any garden centre or (often) service station.

I heard of someone who built a wooden "shed" like structure around his tree. He insulated it very well. Also, another person strung a short strand of christmas lights around his tree, and wrapped it with tar paper and burlap. When he heard that the weather was dropping below a certain degree, he would just plug in the lights until the next morning and then unplug it the next day. I need to wrap my trees this weekend. I finally decided to put them in the ground after keeping them in the shed over the winter.

What i've been doing for the last 2 winters is, bending the tree down to the ground... it's amazingly flexible... I put a stone to hold it down. Then I cover with mulch... You can put a tarp intop of the mulch again for extra protection.
The one year I wrapped with a plastic film that was an old greenhouse film.. and it did the job... but you want to wrap when it gets really cold and unwrap before any early warm days... to avoid molding.

Bass