Build a Simple Cold Frame

Using cold frames is a great way to extend the growing season. These sturdy structures are highly effective in protecting plants and seedlings from cold weather. They comprise a variety of models, including some that are sold in pre-packaged kits. For those who want to keep costs to a minimum, building a makeshift cold frame (right) from a few basic materials provides a quick and easy alternative to a store-bought model.

Space and budget are the two major considerations in choosing the right cold frame; most models feature a slanted design that allows rain and snow to slide off.

Pre-packaged cold frames are generally made of hard, durable polycarbonate plastic and are able to effectively resist hail and other adverse weather conditions.

Kits with built-in frames generally feature a simple design that requires only a hammer for complete assembly.

To ensure that a cold frame is able to absorb a sufficient amount of heat during the day, place the structure along a home's southern or western exposure.

During the hours when the frame is absorbing heat, prop the door open with a wooden dowel to provide ventilation and encourage air circulation (see right). In the evening, close the lid to protect the plants from cold temperatures.

Cold frames are great for over-wintering plants as well as starting seeds. (Note: When starting seeds in a cold frame, it may necessary to provide "bottom heat" (from a source like a heat mat) to get seeds started.)

Cold-tolerant varieties that make good choices for cold frames include pansies, violas and most vegetables.

An inexpensive "instant" cold frame can be created by placing six to eight bales of straw around the area that needs protection, and covering the bales with a storm door laid across the top. If one side of the bales is removed and the cold frame placed against a house wall the house wall can be used as a an extra source of heat. Hay bales can be bought from your local pet shop. They should last several years and can be dug into the soil as an improver when you are finished with them. If in doubt as to the temperature inside the cold frame, purchase a minimum / maximum thermometer to measure the lowest and highest temperatures. Ask for one as a Christmas or birthday present.

Here I have to admit to being a bit of a miser - I have discovered the absolute cheapest method of constructing a cold frame! It's simple really, you dig a hole in the ground, about a metre (3 foot) deep and the size you want for your cold frame. Them simply cover the top with plastic. This gives you a cold frame with sides made out of warm earth - cheap and effective. I do this in a bed which I don't need to use until late Spring.






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