Get a Jump on Spring with a Cold Frame



What is a Cold Frame?

Generally a Cold frame is a constructed bottomless frame, set on the ground.  It has a slopped roof which allows snow and rain to run off.  The size of the frame should be built to accommodate your needs.  The one pictured here, is a good starting size - 4' by 4', 13" high at the back and sloping to 9" at the front.  The lid will need to allow sunlight in, it can be made of traditional glass, like that of an old unused window frame or it can be made from a wooden frame with plastic tightly stretched over it as seen in the picture.  A hinged lid is a very important feature, so that it can be propped open to ventilate the interior as needed

The Cold frame is much like a mini greenhouse, retaining heat and protecting the growing plants from cold, wind and frost.  It can give you a month or more head start on the growing season.

Set your cold frame in a sunny spot facing south.  You can use it as a temporary fixture or a permanent garden.

Make sure the cold frame is set over the gardening spot with lid down at least 10 days prior to planting or placing pots.  This will allow the ground time to warm and help stabilize the internal temperature.

For permanent planting, you are best to plant low growing plants that are somewhat hardy.  You can start your taller crops in pots and keep the pots in the cold frame, transplanting them at a later date when risk of frost has past.

Here you can see Liane has done some planting directly in garden soil, rather than using the ground soil, she has first placed down a black ground cover to discourage grass and weeds from growing up.  She then added a 6" layer of Pefferlaw brand Organic Compost to grow her vegetables and herbs.

She also used the space inside to place potted seedlings and plants for transplanting later.  It's a great way to harden off your plants outdoors without the danger of frost.

IMPORTANT! - There is far more likely a danger of overheating plants than there is of them suffering from the cold.  You will need to monitor the temperature inside the frame daily and open the lid to ventilate it as needed.

Keeping the internal temperature below 25 degrees Celsius is best, if it starts to rise above you will need to open the lid to vent.  If you don't have a thermometer in the box, go by this rule of thumb, if the outside temperature reaches 5 degrees Celsius - open the lid to vent, if the outdoor temperature reaches 10 degrees Celsius then open the lid completely.

Close the lid in the afternoon to trap in the heat for the evening and protect from frost.  Don't forget to water your plants and keep the ground moist.

There are many types of cold frames - they can be as simple as haybales covered with a old window frame to more complex boxes.

Here is a link to build a moderately easy cold box frame on a do-it-yourself web site:

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