If you live in Zone 7, where I do, it is time to have the lids off your cold frames, unless you’ve put sweet potatoes in there to sprout after the tomato seedlings came out and you want the extra warmth. Here in Virginia, in the month leading up to the last frost, we can have weather at both extremes of hot and cold. Having cold frame lids that are easy to adjust or remove completely is an advantage. On the 4’x 8’ cold frame in the photo I have four panels of twin wall polycarbonate. You can see how I make the best use of them at HomeplaceEarth. The twin wall was given to me as one big piece by friends who were replacing it on their solarium. I cut it into the four pieces.
My first cold frame long ago consisted of an old window and a base made of scrap wood sized to fit the window. I’ve been learning more about cold frames and how to use them to grow out transplants ever since. I moved away from using old windows when a friend gave me a piece of safety glass measuring 3’x 6’. (It’s nice to have friends!) I made a wood frame for the glass and put it on a cold frame patterned after directions in Eliot Coleman’s Four Season Harvest. One thing I learned about using old windows that didn’t contain safety glass was that they were a magnet for soccer balls and needed to be in the fenced-in garden area, away from everyday happenings in the yard.
If you don’t have old windows or friends with glass or twin wall panels to give away, you could make lids out of 2x2 pine and cover them with construction or greenhouse plastic. One layer of glazing is sufficient in our area and it lets in the most light. However, if you were aiming for maximum warmth you could put the plastic on both sides, leaving a 1½” air space between. (2x2s are actually 1½ “x 1½”) If you are using greenhouse plastic, you will still have enough light coming through. Making your own cold frame lids has the advantage of making them any size you need to fit your project.
I made the first Coleman-style cold frame in 1999 and liked using it, so I kept that design when I needed a replacement. I paint my cold frames white, because it looks nice in the garden and for safety. It is easy to see at dusk so someone (me) doesn’t trip over it. Cold frames are a treasure to have in your garden. Once you know how to get the most use out of them they will be a continual supply of transplants all year long.
Learn more about Cindy Conner and what she's up to at www.HomeplaceEarth.com.