It's been on my project list since last spring, but I never quite got to it. I've been acquiring the materials and planning to build some cold frames for season extension for a long time, but it was only last week that I finally pulled the trigger and did it. There was really cold weather and snow forecast for our area in the mountains of western Virginia, and I realized that frigid cold and snow would push the limits of the groundcover cloth I had been using for frost protection.
I had a bed of lettuce still growing – volunteers from my harvesting of seeds from the spring crop – and I didn't want to let it die when we could have fresh salad through the winter. So I grabbed two of the storm window panes I had picked up in a batch from someone on Craigslist, took measurements, and built a cold frame to fit the window dimensions.
A few 2x10s and some scrap wood did the trick, and the cold frame was in place before the bitter cold (teens) and snow arrives (we ended up getting about an inch).
The design was simple – a basic box with 2x10s, plus a 2×6 cut diagonally to create the angle for the windows to rest on, and a strip along the back to create a ledge for the windows to rest and pivot on. I'm using a 2×2 the stretches across the length of the box to prop up the windows to provide ventilation – it can be moved all the way back towards the midpoint and create an increasing gap to provide greater ventilation.
I should be able to keep this lettuce growing all winter with proper management of ventilation for warm days. I'll check back in in a month or two to show some progress and relay any lessons learned in my winter gardening.
Have you used cold frames before? What other season extension methods have you tried? Please share in the comments, and be sure to contribute to the discussion in our Gardening group.