What is a cold frame?

You have probably seen these small structures around at some point or another, usually in the colder months in the middle of a garden.  Cold frames are essentially mini greenhouses without all the trappings and are designed to extend the growing season or get an early start on the next season.  The best part about a cold frame is that it can be inexpensive and simple to build, as long as it has a transparent top, solid walls, and placed in a southward direction, it will work.

The fall is the best time to build or order and install your cold frame.  You’ll be glad you did this winter.

If you want to build a cold frame, there is no rigid “standard” way and you can get creative depending on how large or small you want to build your cold frame and what materials you have around the garage or can afford.  The only point of the cold frame is to keep the plants inside warm by capturing the light and heat that enters the clear top inside to keep the plants warmer than the outside temperatures and prevent large daily temperature swings.

There are plenty of cold frames on the market. However, if you want to just try out a cold frame, simply create four walls out of brick or wood, and then put an old window on top as a lid.

1.    Make sure the lid can be moved or lifted because during those unusual really warm spells, you may need to vent the box a little to prevent the plants from wilting or burning.

2.    Make sure the area you place the cold frame in has good drainage. If it doesn’t the structure will collect water and this will drown the plants.

3.    Choose a southern exposure for the cold frame to take advantage of the sun as much as possible in the winter months.


What’s great about a cold frame is that once set up, there are no maintenance costs. If you are getting windows replaced, it’s a great way of re-using your waste. Your extended harvest season will not only add convenience to you life, give you some additional satisfaction, but  will save you money, reduce “food miles”, overall reduce your carbon footprint another smidge.

Perhaps the best use of a cold frame is for fall gardening. Here’s a link to Hume Seeds with their advise on all the different types of fall plants you can grow, and when you should plant them.

As you can see, a lot of great vegetables can be grown including broccoli, beans, peas, lettuce, spinach, cabbage, cauliflower and more.  Extend the growing season for summer crops if you want to try replanting and achieving a second harvest or simply extend the life of summer crops like herbs. Finally, in the early spring, cold frames can be used to get a jump start on your summer planting by allowing for starter plants to be planted in the ground early on, with the cold frame providing warmth that will sustain them even if the outside weather isn’t perfect for growing them. With cold frames being so easy to make and experiment with, it’s an excellent idea to try one out in the fall, and see if you can grow some fall/winter vegetables because there’s no risk if it doesn’t work, and all you have to gain is a reduced carbon footprint and fresh produce on your dinner table.

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