I have known for the past two weeks that the subject of my blog would be coldframes—I don’t always know what I’ll write about that far ahead. However, I thought the title would be Coldframe Transplants. Before I began writing the new post I reviewed my previous posts about coldframes and realized that I had written much of what I would say this time in Use Your Coldframe All Year last May. So, I encourage you to read that post. I had taken some good photos of my coldframe in April and realized that I could focus this post on coldframe lids.
The coldframe in the photo is 4’x 8’ and has four 2’x4’ lids made from twinwall polycarbonate panels. They were made from one 4’x 8’ twinwall panel that friends gave me when they were replacing the glazing on their solarium. I have considered putting wood frames around the twin wall panels to protect the edges, but haven’t gotten around to it. With a coldframe this big, using one panel for a lid would be awkward to use and to store. My previous coldframe was 3’x 6’ because I was given a piece of glass that size that I framed in wood. One advantage of that lid was that it was heavy enough not to blow off in the wind when I had it lifted on one side for venting. A disadvantage of that lid was the weight and size when I stored it in the barn for the summer.
I have never liked using hinges on coldframe lids because hinges would limit their use. I want to be able to move the lids around or take them off completely. When I taught at the community college one of the projects I assigned was to plan a season extension structure for a 4’x 25’ bed—complete with a drawing of the design, list of materials, and how it would be used. If the students chose to use a series of coldframes I always warned them I would take off points if there were hinges on the coldframe lids. Sometimes you need to take them all the way off. If you tilt them back, as in this photo, there needs to be room for them behind the coldframe.
These panels are relatively light. If I had them lifted on one side to vent, the wind may blow them off. It can get pretty windy in the spring. I was gone for five days the second week of April. Things were just coming up in there, so I wanted to keep the lids on while I was gone. However, looking ahead to the weather, it looked like some days would be quite warm. I decided to turn the panels parallel to the long sides of the coldframe and lower them a bit, leaving a vent space at the top. That would keep everything warm enough, but not too hot. It was nice that the day before we left for the trip we had an inch of rain—with the panels off.
Sometimes I stack the panels on the coldframe if I want to vent it a little more than I did when I went on the trip recently, but still keep some protection there. If I was going to vent that way more than a day or two, I would not stack the panels, but take two away so as not to prevent light transmission. The extra panels can lean against the side or back of the coldframe, ready to put back on when needed. When I store the panels for the summer they only take the footprint of one panel.
Your coldframe lids might be old windows or wooden frames covered with plastic. Consider all the different ways you might use them before building your coldframe, so as not to limit your possibilities. By this time of the year, you may be frost free and can store your lids for the summer, but your coldframe will still be of service as a space to grow transplants all through the growing season.