Building Cold Frames

September 25, 2010

The rains have started early this year and my little peony seedlings are drowning! To protect them from the weather, I built cold frames.

There are hundreds of different plans for making cold frames, both online and in books. After a search, I chose a designfrom the Better Homes and Gardens website, mostly because it looked simple, cheap, and interesting.

For those of you who aren’t familiar with the concept, cold frames are like miniature greenhouses, usually no more than 2 ft deep, with a transparent sloped roof to shed rain and snow. They insulate tender plants, especially seedlings, from excess water and weather extremes, and if placed in a sunny location, can significantly extend the growing season by keeping veggies warm. Often they are slightly buried or otherwise insulated, but my peony seedling have proven themselves quite hardy in our winters, so I didn’t add in those extra measures.

Cutting the plywood

Cutting the plywood

Assembling the frame

Assembling the frame

One thing I liked about this design was the idea of cutting all four sides of the cold frame out of one big piece of plywood. Very clever. After drawing out the lines, I proceeded to cut the plywood sheet. I also like how the sides are joined: with perforated steel angles, rather than nails. The whole design calls for 25 bolts and 45 screws…per cold frame!

Assembly In Process

Assembly In Process

Once all the sides were cut, they seemed to go together fairly neatly. The next step was to construct the wood frame for the lids. The plans called for 1 x 3’s of clear pine, but I used cedar instead so it would last longer. The sides are attached using a steel L-plate and reinforced with triangular pieces of plywood.

Corner Construction

Corner Construction

Once the lids were assembled, the plans called for wrapping them in a single layer of 6mil clear plastic. This was one part of the design I wasn’t wild about. I looked into purchasing a clear sheet of acrylic or plexiglass but piece big enough to cover my cold frames was prohibitively expensive, so I went ahead with the clear plastic idea, figuring I could always swap it out later if I found a sheet of glass or plexi at a reasonable price.

Close-up of finished corner

Close-up of finished corner

Plastic sheet over lid frame

Plastic sheet over lid frame

After I had wrapped the plastic around the lids, I reattached the hinges to the boxes and positioned my new coldframes on my seedbed.

The finished product

The finished product

My coldframes are now finished and my seedlings snugged away inside. It’s a good thing, too, because the weather is calling for lots of rain tonight. Now I won’t have to worry about them drowning!

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