As mild as our winter has been I think I will set out more cold frames to use. Even in the cold of the winter I still grow greens. But the snow has melted again and we have a week of above warm weather so I will bring out two additional cold frames to use and have one prepared to use as a hot bed.
I have to admit I cheat in my cold frames. I have the frames built a little larger than I normal would so that I can line the inside of the frame with the smaller clear milk jugs filled with water.
I start with warm water and the sun will keep the jug water warm and that additional heat will keep the cold frame warm enough to grow a few more vegetables than just greens. If by chance the temperatures drop I cover the frame with a blanket. Ands if Mother Nature really decides to change weather on me I have the cold frame close enough to plug in a small watt light bulb to keep the temperature up.
I have only used the light bulb one time and I was experimenting with seed germination at that time. You can also use a waterbed heater in a cold frame if you hit a cold spell, its works great!
You can also a hot bed, which is the same as a cold frame except when you assemble it you dig the soil deeper and add fresh manure under the soil. The manure starts to work and will keep the soil warmer than the traditional cold frame.
I lengthen my growing season by at least two months for the spring and fall. I do have a greenhouse but heating takes time and money so I use the frames at first them move the greenhouse later.
If you would like to try a cold frame out here’s a quick frame to make using straw bales. It will set up quickly and you can see if you actually like gardening using frames.
Straw Bale Cold frame
You will need four or six square straw bales, one or two old window frames with the glass intact, old newspapers, and potting soil or compost. (Wood chips and leaves would also work)
Find a location that gets as much sun as possible. I try to choose a place close to the house so that if I need electricity I can get to it quickly.
Arrange four straw bales in a square. Or if you want a double cold frame, arrange six bales in a rectangle.
Wrinkle up the old newspapers and fill the cold frame about one-fourth full from the bottom. Then cover up the newspaper layer with compost or potting soil until half full. I try to use newspaper with as little colored ink as possible.
For successful crops choose your plants and crops plants carefully. Use the most cold resistant ones in the later part of the winter such as greens and cabbages and the more delicate ones in early fall and late spring. Place plants in the soil of the cold frame, inside the straw bales. Cover with the old window. I often top the glass with a plastic cover. The plastic will cut back on some of the ultra violet rays that will sometimes burn tender new plants.
It’s wise to wear gloves when removing the glass top of your cold frame to advoid getting cut or getting slivers from the window frame.
Occasionally move the top off to the side to allow air in when temperatures are above 45 degrees Fahrenheit. This strengthens you plants and allows them to get used to air currents. It will also start the hardening off process of plants to direct natural sunlight.
Keep a thermometer handy and check the temperatures both during the day and before nightfall. If it’s warm out, prop the lid open or take it off. If the temperatures are cold use the milk jugs, an electric light or water bed heater if necessary and cover the cold frame at night.
I live in a cool Zone 5 so I have to keep an eye out for cold temperature dips. You may not have that problem.
Cold frames can be used even in the coldest climates. My friend lives in a Zone 2 and grows crops in her cold frames and hot beds all season long.