Extend gardening season with a cold frame

Mike and Penny Irving

Cold frames provide a place to start vegetables early, are perfect for hardening off transplants – transitioning the young plant from an indoor environment to an outdoor environment – and extending the growing season into the winter months. A cold frame is also small, portable, and easy and inexpensive to build.

To build your own cold frame, you will need:

  • A 1-inch by 6-inch (1×6) plank of spruce, pine, cedar – whatever your budget can afford.
  • 2-inch by 2-inch (2×2) studs for corner pieces or brackets.
  • Old windows.
  • Hinges and screws for the window(s).

The cold frame we’re describing here will be 12″ high in the back and 6″ high in the front.
Start by getting wood-framed windows. Look for used windows available on websites such as Kijiji or other source of used windows, often from a renovation.

The size of your cold frame will depend on your window size. You can make a single-window cold frame, or make a larger cold frame by using two window frames side by side. The window will sit on top of the frame. Construct the frame so there is a slight overhang of the window in the front. This makes it easy to lift the window.

Start the cold frame with the 1×6 plank and cut the wood to the size of the window frame.
Cut a second 1×6 length and attach to the top of the back piece with a 2×2 length and secure with screws (see pictures). If you prefer, brackets can be used instead of a 2×2 to secure the frame.

Cold frames let you start your garden earlier in the year and extend the growing season into fall and winter. Photo credit: Penny Irving.

Measure the side length and cut a 1×6 to that length, then cut it diagonally, corner to corner to obtain the angled side pieces.
attach it to the windows to the frame with hinges at the back. Add handles to each side of the frames for easy lifting.
We use wooden stakes to support the window when open or partially open.

If you don’t have a glass window, a lid can be made by constructing a wooden frame and covering it with heavy-duty clear or opaque plastic sheeting. A staple gun can be used to staple the sheet of plastic, to hold it tightly over the frame.
We found this to be the cheapest way to construct a cold frame that lasts. Wood such as cedar will last longer than spruce. But so far, our spruce frames have lasted 5 years and are in great shape.

Penny Irving is an active member of the Atlantic Master Gardener Association and member of St. Margaret’s Bay Gardening Club. Mike Irving is her husband and gardening partner.

This story was first published in the March 2023 issue of The Masthead News.