Jump Start your Garden with a Cold Frame

August 23, 2010

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As I was thinking about different options on what to share with you today, I decided on cold frames. Since it’s time to begin fall planting, give or take a few weeks depending on where you live, this is a good alternative to indoor seed-sowing issues, like space for shelves, lighting, etc.

Cold frames are bottomless, sloped greenhouses on a much smaller scale, with four sides and a clear lid (glass, fiberglass, heavy plastic, or frost cloth) that opens for ventilation, and gardening. A typical frame is about 3 x 6 feet with an 18-inch back and a 12-inch front wall. You can purchase a kit, or make your own from scrap wood by using the instructions at, http://www.gardenhelp.org/greenhouse/garden-construction-coach-on-how-to-build-a-cold-frame/

The function of a cold frame is to protect plants against harsh weather. If you don’t have the time or means to make a four-sided cold frame, an A-frame will work. (If using old windows, as seen in the photo, be sure to safely remove all lead-base paint that could chip and peal.) Place both structures on level soil, in a raised bed or directly on the ground. To keep critters out of raised beds secure a sheet of half-inch galvanized wire on the bottom.

Because the ground is cold, it needs insulating. The easiest and most economical source is a thick layer of compacted straw under the planting soil. For extra insulation, mound straw or soil around the outside bottom edges of your cold frame. The straw will rot and can be recycled in the compost bin after use. On nights with extreme cold, cover the lid with blankets.

Whichever structure you choose, it needs six hours of sunlight to collect and retain solar heat. Although the accumulated heat protects the plants from frost damage (and promotes germination and growth), be sure to prop the lid on sunny days or the interior will get too hot beneath the solar-heated lid. The ends of a cold frame should face south and east, with the back wall standing at the northern edge. Choose a site close to the house or kitchen (you’ll appreciate this on winter days, especially if you live in snow country), with a nearby faucet for watering and power if using heating cables, mostly needed in colder regions of the country. Other cold frame uses include:

  • Growing lettuce and radishes 
  • Root cuttings of some woody plants
  • Early start for warm-season vegetables
  • Force bulbs and other flowering plants early
  • Shelters tender perennials as they “harden off”*
  • Aids early spring seedlings as they “harden off”*
  • Protects small potted plants from severe weather

Other cold frame benefits:

  • Suitable for small landscapes
  • Quick & easy weekend project
  • More economical than a greenhouse

*Gradual exposure to light and temperature changes before transplanting.

Copyright © 2010 Dianne Marie Andre



  1. Most city houses are situated on rectangular-sized lots. My house faces north so my backyard has a southern exposure. The sides of the house get the sunrise (east) and the hot afternoon sunset (west). I am not sure how I can place a cold frame where you stated “the ends of a cold frame should face south and east, with the back wall standing at the northern edge”. However, the A-frame sounds doable.


    • Betty,
      You’re right—cold frames don’t “fit” every situation. When I lived in town, my husband divided the backyard. Half was the typical grass and shrubs, and half was a garden area where a cold frame would work. However, not everyone has favorable outdoor space/layout or wants that type of landscape design. I’ve seen some cold frames made of old shower doors leaning against a fence or an exterior wall. Certainly, a cold frame is not a “must” if one lives where winters are mild. Just an added bonus if you don’t have indoor space or a greenhouse.–Dianne


  2. Good morning – very interesting blog post.

    Would you recommend glass for a cold frame or plastic/polycarbonate?



    • Bill,
      I prefer glass, which should be tempered safety, R-5. With glass, your plants will get the maximum light, it’s easy to clean, and I personally like the look of glass. The plastic-polycarbonate should be rigid. It’s unbreakable, but it does scratch. I understand this product is easy to cut. Sometimes we have to use what’s on hand. –Dianne


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