You could try making a teepee with clear plastic. Or get some long thin PVC pipe and sink either end in the ground around tree and connect the pieces in the center with a x-shaped connector and cover it with clear plastic.

Well, we have built a cover for our peach tree and hope it will stand up to our cold, wet, windy spring weather. I thought I would post a pic of it. We built a cedar box around the bottom of the tree and attached some bendable plastic pipe by way of u-fasteners. Added the plastic to the top. It was very bendy in the wind so DH drove steel stakes in to help support the plastic. I hope it works!

Here is a link that might be useful:

If that doesn't work maybe four posts to support a permanent clear corrugated or? roof, we have one over a tomato bed. You could have clear plastic drop flaps which could be removed once the tree has leafed out.

Annette