It was a cold and snowy weekend here. I was hoping to work on the finishing touches of our hoop house but it was just too cold. Instead, I was able to work in my garage and build a new cold frame.
If you would like to see step-by-step instructions on how I built it, vist my GardenDesk blog. For this post, I wanted to go over what a cold frame is and why every frugal gardener should have one.
A cold frame is essentially a bottomless box with a covering of glass or clear plastic sheeting. These coverings are called "lights" because they collect the warm sunshine to heat up the plants contained inside the frame. This "box" can be placed directly over a portion of your garden bed to protect plants that are growing in the ground. You also can simply use your cold frame to place potted plants inside. The "lights" are constructed on the top of the frame at an angle - usually somewhere between a slight angle to a 45 degree angle, facing south to maximize mid-winter sun.
I consider a cold frame the gardener's single best investment because it enables you to extend the growing season for several months. In many areas, a cold frame will aid you in growing cold-season greens all winter long. The more months I can provide my family with healthy organic vegetables, the more money I save!
The cold frame is not a new invention. It dates back to the beginning of cultivated farming. It is very versatile because you can build it to suit your space and your needs. It can be any length as long as you can get the tops to fit. Many times you can construct one out of recycled or reclaimed materials such as old storm windows. My first cold frame was made from an old shower door. I do have to pause here to issue a warning however. Keep in mind that if you use glass as the "lights" that it can become dangerous if someone steps or falls onto it. I switched to using greenhouse style plastic sheeting when I had small children "helping" in the garden. Always remember, safety first.
So how does the cold frame work?
It protects plants from wind and freezing. When the lid is closed, it creates a micro-climate with the temperature being higher than the outside temperature. Granted, the difference may only be 5 or 10 degrees different in the winter, but that is significant when you also cut down the wind and the moisture that leads to freezing.
So what are the primary uses for a cold frame?
If cold frames are so good, why doesn't everyone use them?
Mainly I would have to say it is because they haven't fully considered the benefit of having them in the garden. Another reason could be because of the extra work it takes. Yes, they do require some extra work. The drawback with using coldframes is that you have to constantly be aware of the weather outside. A coldframe needs to be vented if there is direct sunshine on it or if the temperature significantly rises. The power that we rely on to keep the veggies warm can quickly become powerful enough to cook those veggies.
This is not as much a problem in the middle of winter, but you have to be careful in the spring and fall. If you can't be ready to open or close the frame based on the changing weather, you can purchase an automatic venting arm that will do it for you. We have never had to rely on one, but I do admit that in the Spring I am always thinking about how the plants in the cold frame are doing. When hardening off vegetables in late Spring, we keep a thermometer in the frame that broadcasts the temperature to a unit in our kitchen. When we notice the temperature getting too hot, we open the lid further. If we get an unusually hot and sunny day, we take the top off entirely. It can actually be fun trying to figure out what the weather will do. The venting requirements varry depending upon the season. On most days there are no problems at all. Even when it gets tricky, the benefits still outweigh the hassles.
I strongly encourage you to use a cold frame to help you grow more food for an extended period. If you have used them in the past, but haven't lately - now is a good time to re-consider them. If you have never used them before - now is a good time to make yourself a small frame. You can see a very simple design on my post Step by Step How to build a Cold Frame.
If you are like me and it is winter where you are, building a coldframe while it is snowing outside will make you almost forget the cold and long for warm gardening ahead!