Cold Frame Gardens For most home gardeners, the start of the growing season comes too slowly and the end of the season comes too fast. We certainly can’t stop mother nature, but there are ways to extend both the beginning, as well as the end of the the season. One of the best things you can do is use cold frames in and around your garden.
By definition, a cold frame is nothing more than an outdoor structure consisting of a bottomless frame and a glass/plastic top, which is heated through sunlight and is designed to protect plants from cold and adverse weather conditions. They are simple to construct and can add weeks to your growing season.
Guide to start cold frame garden project
Here are some proven ideas to get you started on a cold frame gardening project. First, you must decide what type of structure you are going to use. The easiest thing to do is simply to gather some bales of straw, place two on the front, two for the back and one each on the sides. You could also construct your frame out of bricks or cement blocks. Perhaps the most common however, are frames made out of wood. If you want detailed plans on how to build a cold frame, just go to the internet. There are literally hundreds of pre-designed cold frame plans available on the web and kits can be purchased at garden centers and home improvement stores.
Now comes the most important part: The TOP. The only way you are going to have a successful cold frame design, is to have a draft free top through which sunlight can pour in and create a warm and cozy mico-climate for your plants. Old windows make excellent tops, but any glass, plexiglass or strong plastic sheeting will do. I particularly like unused shower doors because they are the perfect size. You don’t want to use anything that is wider than four feet, which would make access to the middle of the cold frame a bit difficult. The length of your frame is never an issue.
Temperature control is very important to successfully growing plants inside your cold frame greenhouse. A well constructed frame can overheat very quickly and it is best to err on the cool side, especially in the spring and fall. In general, if the outside temperature is below 30 degrees leave the top on. If it is above 40 degrees, prop open a few inches in order to vent out excess heat. If you have a day with the temperature over 50, you should remove the top completely. Replace the top late in the day in order to trap some heat for protection from plunging night temperatures. It is also a good idea to cover the top at night with some sort of insulation, like a blanket or layered newspapers. Even snow is a good insulator. In the morning, simply remove the insulating layer and let the sun work its magic.
In the spring,“hardening off” your seedlings is a critical step in the longterm vitality of your plants, and cold frames are perfect for this. Plants started from seed indoors and under grow lights need several days of part time exposure before fully transitioning to their new life outside in the garden. Trays of seedlings can be placed in the cold frame for a half an hour on day one, and increased by another 30 minutes everyday after that. Just make sure the temperature in the frame doesn’t get too hot! Seedlings are tougher than you think and can easily tolerate a bit of cool, say 50 degrees, and after a couple of weeks they will grow into strong healthy plants ready for the garden.
You can put your cold frames away for the summer, but by autumn they should come back into play. September is a good time to start many quick growing plants that will mature later in the year. Broccoli, beets, chard, green onions, kale, various lettuces, radish and spinach all are excellent crops that will thrive late into the winter if protected by a cold frame.
A final word of caution. Cold frames can be very addictive! Once you discover how easy they are to build, and how productive they can be, you will find yourself adding more and more. It is a joy to see cold frames brimming with young plants in early April, while eating lettuce picked from the garden in December is a real treat!
In areas where the growing season lasts for about six months, cold frames can extend the season to nearly a year round pursuit. Start small, learn along the way, and pretty soon you too will become a cold frame gardening expert.