Ever hear expert gardeners talk about cold frames and how amazing they are for the growing season?
What are ‘Cold Frames’?
Cold frames are similar to greenhouses in that they are structures with rigid sides and a glass/plexiglass roof, which are used to house garden plants. That is where the similarity ends. Cold frames are usually much smaller than greenhouses, can be permanent or portable, and, as the name implies, are used in the fall, winter and early spring but are not heated. Instead, they depend on the heat and light provided by the sun to encourage growth. They create microclimates which provide several important degrees of air and soil temperature insulation, as well as shelter from wind.
A typical cold frame is built with a hinged, recycled window or a piece of plexiglass on top to capture the sun’s rays and trap the heat and moisture. The frame itself is made of wood, with the front edge of the box is lower than the back edge to provide an extra angle with which to maximize exposure to the sun. The angle also allows rain and snow to easily run off the box during rough weather.
When setting up your cold frame, it’s important to orient it to grab as much sunlight as possible. Building it close to your house means you can keep an eye on the internal temperature (and open the window if needed), as well as keep it free from snow and well irrigated.
The extra value of a portable cold frame is that you can move it to various sections of your garden as needed, providing mobile protection for early spring and fall transplants from frost and cooler weather, hardening off, and protecting cold season greens into the winter months.
When should I use a ‘Cold Frame’?
A cold frame is typically used in the fall to provide extra protection for those parts of your garden that are not yet ready for harvest. They can also be used in the spring when you wish to jump-start your growing season by planting seedlings ahead of time. In certain cases, they can also provide a permanent home for vegetables requiring a winter harvest.
Which plants can I use in my ‘Cold Frame’?
Cold frames are useful for giving any seedlings a jump-start in the spring. In the autumn, expect your best results when using them to propagate a succession of vegetables like leafy greens, root crops, leeks and herbs to name a few.
A temporary cold frame vessel gives you another option to try your hand at over wintering tall crops like kale and leeks.
Insider Secrets for building your own ‘Cold Frame’
We’ve been quite successful with our foray into using cold frames to extend our growing season, both at the beginning and the end.
You may choose to purchase a cold frame kit from any gardening centre or hardware store or you may wish to build a simple one from scratch. We constructed ours using a retired, replacement window or a piece of used plexiglass for the lid and recycled lumber for the box. Inside, we use a layer of straw or leaves to insulate our plants, especially our root crops such as carrots or beets. Constructing the box with bales of straw instead of wood,will increase the insulation value of the frame as well as provide great mulch for your garden in the spring.
Sinking your cold frame into the ground by several inches helps ramp up the insulation value and crop protection from outside elements.
Whether you decide to buy a kit or make one yourself; whether it is permanent or temporary; whether it is made of wood or straw, enjoy your new cold frame and experiment with which vegetables you can enjoy for a longer period of time!
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