Cast aside winter with a cold frame

Wednesday, February 19, 2003

P Using simple materials, you can build a greenhouse and get a jump on spring planting.

I don't know about you, but I am getting a little tired of winter. As I write this column, I am listening to another winter storm advisory on the radio. Is spring going to ever get here?

Even if Mother Nature is not cooperating, you can still get a taste of spring by putting together a cold frame for a small part of your garden. With a cold frame, you can get one or two month's jump on planting lettuce, spinach and radishes. Here's how:

Start by building a foundation over part of your garden. You can use a 2-by-6 or a 2-by-8 board standing on edge. Just make a box out of the lumber. You can also use bricks, concrete blocks or straw bales for your foundation. The size of the box will depend upon the size of the glass that you are going to put over it.

When choosing a material for your foundation, make sure that pieces fit together tightly, because you don't want a draft inside your cold frame. You also need to make sure that the material you fit over the top of the foundation fits very snugly with the foundation for the same reason.

Next find a piece of glass for the top of the cold frame foundation. I would use glass that is in a frame because you will be opening and closing the cold frame quite often. An old storm window makes a great cold frame covering.

You can also use clear plastic mounted over a frame. Although plastic does not let quite as much light in as does glass, it is lighter and usually cheaper than glass.

So how does a cold frame work? Basically what we are talking about is using the "greenhouse effect" to your advantage. When short light waves from the sun move through a pane of glass or through clear plastic, they become elongated. The elongated waves cannot reradiate or move back through the glass or plastic into the atmosphere. Therefore this energy builds up under the glass and heats up the soil and air under the cold frame.

Because the soils and air temperature are warmer under the cold frame, you can now plant your lettuce, spinach or radishes right into the soil under the cold frame. You will be surprised to see these plants germinating and thriving in the cold frame even in December and January.

Keep in mind that as spring approaches, the temperatures may get extremely hot inside the cold frame. To keep this from happening, remove the glass or plastic cover over the frame during sunny days. Just remember to place the cover back over the cold frame at night. If you don't you could lose your young and tender plants to frost or freeze damage.

The system I have described is not something new. Cold frames, or "greenhouses" as they are referred to in Europe have been around for hundreds of years. Kings and queens were using these structures to produce fresh vegetables and flowers for their dining tables.

If winter weather has got you down, and you want to get a jump on spring, put together a cold frame. Usually you can find materials around your house that can be used. If not, then go to your local lumberyard and purchase the materials you need. You really don't have to spend a lot of money to get going. With a little effort and very little expense you can be growing your salad fixin's in no time.

Send your gardening and landscape questions to Paul Schnare at P.O. Box 699; Cape Girardeau, Mo. 63702-0699 or by e-mail to

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