A cold frame is an enclosed framework that allows you to grow garden crops in winter. The cold frame can be a simple three- or four-sided structure build of scrap wooden boards or concrete blocks that adjoin an existing structure. The four sided cold frame can be a free-standing structure.
With a little bit of care, you should be able to have fresh vegetables 12 months of the year. The cold frame will also give you a head start in sprouting seeds for planting in spring.
Just before building your cold frame, select a location that receives sunlight for most of the day. The cold frame should be placed in a location facing south. The second best location is to place your cold frame in an area facing west. Refrain from placing the cold frame in the shade of overhanging trees. Select an area with a gentle slope for better drainage.
You can use 2nd hand scraps of lumber to construct your cold frame. Old window sashes can be used for the top. The length and depth of the cold frame is determined by the size of the covering window sash that you choose. The sides of the cold frame can be made of wood or concrete blocks. Build the cold frame to a height that makes it possible for you to easily reach inside to tend your plants.
Dirt for the cold frame can be made from regular gardening soil. Cover the soil with a one inch layer of organic fertilizer or dried manure and till to a depth of 12″-18″. The compost or manure will improve drainage and provide nutrients for your growing plants. Plants grown in a cold frame generally require less fertilizer than those grown in an outdoor garden.
The cold frame can be converted to a hot bed by adding a waterproof underground heating cable on or under the surface of the soil. A heat lamp can instead be installed above the soil to provide needed heat when the weather gets very cold. Alternatively, you can cover the cold frame with an old blanket or burlap sacks to protect from extreme cold.
Insect pests are less of a concern when you grow in a cold frame. The only real problem can be snails. These can be removed by hand and disposed of.
During the warmer days of winter, you will need to open the door of the cold frame to allow for air movement. You can use sticks to prop open and support the cover.
With a cold frame, you will be able to grow a variety of garden vegetables in fall and winter. Some of the easiest food crops to grow are lettuce, carrots and radishes. Herbs can also be successfully grown in the cold frame in winter. Cabbage, kale, Brussels sprouts and collard greens also do well when grown in a cold frame.
The cold frame can be used to germinate seeds in early spring and acclimate them before transplanting to the outdoor garden. If you have a greenhouse, you can start your seeds in the greenhouse in early spring then transfer to the cold frame to harden off before transplanting to the outdoor garden. You can also use the cold frame to extend the autumn growing season.
Set up a cold frame to extend your growing season up to twelve months. Fresh vegetables from you cold frame can yield fresh vegetables for salads even for Thanksgiving and Christmas dinner.
Robert Gregory Donaldson is a writer and gardener living in Reno, Nevada where he grows a variety of food crops.