Extend the growing season for fresh veggies with this simple cold frame.
Endless Harvest
Credit: Joseph De Sciose

Imagine picking crisp, fresh vegetables from your own garden during the coldest parts of the year. When the grocery stores are offering only frozen peas, you can create a cold frame that will give you the ability to grow vegetables throughout the year. Cold frames are easy to build and cost only about 20 bucks. They are also a great way to start vegetables outdoors in the spring a few weeks earlier than you normally could.

How It Works
Cold frames are basically miniature greenhouses. They trap the sun's heat throughout the day and then slowly release it during the night. This gives up to a 10-degree boost in temperature for young seedlings. For instance, if the temperature goes down to 25 degrees (a killing frost for most plants), a cold frame will keep the minimum temperature at around 35 (warm enough for your cool-weather vegetables to survive).

To increase the effectiveness of a cold frame, position it in a sunny, south-facing location. This allows the maximum amount of light to reach plants throughout the day. Also, consider putting the frame next to a wall or hedgerow to give plants added protection from cold winter winds.

Build It Now
While there are lots of options for constructing a cold frame, I've found that using recycled wood window sashes and plastic sheeting is the easiest and cheapest. Find window sashes at flea markets or used-lumber stores, or use plastic instead. Follow these steps to create your own.

Step 1: A cold frame can be as big or small as you need. This one is 4 x 2 x 2 feet with triangular sides. Build it using cedar or pressure-treated 2 x 2s. Attach the pieces with galvanized L brackets and 1 1/2-inch-long decking screws.

Step 2: Cut pieces of 5-millimeter-thick plastic sheeting to fit the sides and back of the frame. Staple the plastic to the top and sides of the frame.

Step 3: Using two hinges per window, screw the sashes into the frame at the top. Make sure the sashes close tightly on the bottoms and sides. Use insulation such as weather stripping to fill in any gaps. Add a coat of paint to the sashes to preserve the wood and offer a touch of color in the winter garden.

MATERIALS (for a 4- x 2- x 2-foot frame)

  • 3 (4-foot-long) cedar or pressure-treated 2 x 2s
  • 2 (2-foot-long, 10-inch) cedar or pressure-treated 2 x 2s
  • 4 (2-foot-long) cedar or pressure-treated 2 x 2s
  • 4 galvanized L brackets
  • 1 box (11/2-inch-long) decking screws
  • 16 square feet (5-millimeter-thick) plastic sheeting
  • staple gun with staples
  • 2 (2 x 2 foot) window sashes
  • 4 stainless steel hinges
  • 1 roll weather stripping insulation
  • 1 pint indoor/outdoor paint
  • 2 extra 2 x 2s to prop open cold frame

"Endless Harvest" is from the December 2005 issue of Southern Living.