Well this past week in the mid-Atlantic we’ve seen snow, ice, rain, sleet, and all that wonderful winter weather. I’m glad I got back from vacation just in time to throw the cover on my cold frame. Last year I essentially had a few posts holding up a plastic sheet which was then held down by several bricks around the corners. While it did the job just fine, I also started the spring with several broken branches due to the wind blowing the plastic up against the frozen branches.
I though this year I’d try to create a better (while still cost effective) solution. I decided to build a simple cold frame out of PVC and cover it with two layers of 3mil plastic sheet. The total ran around $150. For the frame I used 1 inch PVC pipe and for the ribs I used ¼ in PVC pipe. I’ve read several articles that say that the plastic sheeting *is degraded by the sunlight*(thanks Brian). However, since the price is very cheap I don’t mind replacing the sheeting, even if I have to do it every year. I also considered a wood frame for more stability, but ultimately I went with the PVC so I can completely dis-assemble the structure in the spring.
A cold frame is a great solution for winter protection for a few reasons. First, it creates an air bubble which makes changes in temperature occur slowly. It can help your trees adjust if there is an unexpected cold snap. Second, it blocks the harsh winds during the winter which can really dry out your trees quickly. Finally, it shelters your trees from precipitation, which it’s typically not harmful to them, but excess ice can lead to broken limbs.
Happy Holidays!
Bonsai Prelude 
That looks really nice. I need to make one myself next year.
It is not a reaction pipe to plastic sheeting. It is just that the plastic degrades because of the sun. It just breaks down over a couple of years. You just have to replace it . Not a big deal just be careful of wet snow as the weight can get a bit much.
Brian
Ah I gotcha. Thanks for the clarification!