Cold Frame Gardening

February 17, 2006

Cold Frames are great for stretching the garden’s growing season at both ends. In the spring cold frames provide a sheltered area for seed starting and to harden off transplants that were grown indoors.

During the fall, cold frames enable you to harvest fresh vegetables longer by protecting your plants from frost and cold temperatures.

Cold Frame Styles and Construction

Portable Cold FrameBuilding a cold frame can be as simple as attaching a discarded window sash to a box shaped framework of wooden boards or by placing the window sash over a group of straw bales arranged to form a rectangular base.

Instead of constructing a homemade cold frame, you can purchase commercial units made out of high tech materials that are designed to retain warmth and transmit sunlight to the plants growing inside.

Inexpensive models are available that are constructed with a plastic or metal tube frame that’s covered by a transparent, woven plastic fabric. This style of cold frame is lightweight, portable, and an easily be moved from one section of the garden to another, making them ideal for use in raised bed gardens.

Permanent Location Cold FrameThe more expensive types of cold frames use an aluminum framing that’s covered with twin walled poly-carbonate panels. These units are sturdier and provide better insulation, but are not as portable and usually remain in a permanent, fixed location outside of the garden.

Cold Frame Gardening During the Fall

For growing fall gardens, plants can be sown directly in the fixed location cold frame during late summer, or winter vegetables that were planted in the garden beds can be covered with one of the portable style cold frames.

In cold northern climates, even with the shelter of a cold frame, plant growth will slow or stop as temperatures drop below freezing. But the cold frame will enable you to continue growing and harvesting organic vegetables well beyond your normal growing season.

When spring returns, many of the vegetables that were planted in the cold frames the previous fall will resume growing to offer extra early fresh produce at a time that the garden’s beds are still frozen and inactive.

Using Cold Frames in the Spring

Leafy Greens Growing in Cold FrameAt the end of winter the cold frame can be used as a nursery bed for starting seedlings of lettuce, kale, spinach, and other leafy greens. Sow the seeds thickly and let them germinate and grow inside the cold frame until spring arrives. When outdoor conditions are suitable the seedlings can be thinned and transplanted from the cold frame into the garden’s raised beds.

Cold frames can also be used in the spring to harden off transplants which were started indoors and grown under lights. Placing the flats or containers of transplants inside the cold frame will allow them to gradually adjust to the harsher growing conditions encountered outdoors, without the need to bring the plants back inside during the night.

Crops growing inside cold frames can survive with little or no watering or other attention over the winter months. But you will need to keep a close eye on the plants growing in cold frames during the fall, and especially during the spring to ensure that they receive sufficient moisture and to vent the cold frame to prevent plants from overheating on warm days.

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  • Henry Lees

    Been doing a lot of gardening from early childhood picking up road apples for my grandmother’s garden to now, from using calcium and epson salts for my tomatoes, to matches for my pepper plants. But I still find new info from this site to improve my knowledge for gardening. Keep up the good work. (Hank)

  • Kenny Point

    Ahhh, the old matches next to the pepper plants trick, I haven’t heard that one in a while. Hank, thanks for visiting the site and for the kind comments. Please stop back soon and let your gardening friends know about the site.

  • Little Hawk


    What is this about epsom salts for tomatoes? First I have heard of this. Would you explain more about that, please. In the northwest it is hard to grow tomatoes, maybe this is a trick that will help. Thanks

  • Mike Timbrook

    My God, this site has everything I need to know about vegetables, Thank You.

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  • Deloris Stone

    I always put a handful of powdered milk and epsom salts in the holes, mix it up good and then plant my tomatoes. Have a great crop every year. It gives them the magnesium and calcium needed to suck up the nutrients they need or something like that.

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  • Wayne Kennedy

    glyphosphates [Round-Up] may chelate Mg out of soil. I just took 300mg of Magnesium Citrate because I just found out today supplementing with Vit D increases need for same as well. So it would make sense the plants would also need it to metabolize the [egg shells ect.] Calcium plants use a lot of. ???

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