What is a cold frame and how can it extend my growing season?

Photo Credit: Denee Bex | Special to the Drum

January is the coldest time of winter and I always get a little antsy. I know spring is just around the corner and I just have to get through this month before it starts to warm up. One way to get a head start is to put out my cold frame. A cold frame is a temporary or permanent structure that goes over your raised bed to create a microclimate within the structure. It is like a mini greenhouse right over your garden.


I use a temporary frame to set up over my beds about a month or two ahead of the last spring frost. I have raised beds that measure 4×8 ft. so I created a temporary structure that I can pop over my raised beds. This way, the inside of the bed warms up, thaws the soil faster and allows me to plant cold-tolerant vegetables just a little earlier. In my area, my last frost date is at the end of May, so anything I can do to get a head start will get me that much closer to vegetables on my plate. I realized over this winter that I have about a good five months of growing season and seven months of cold. What a short season! So, I need to do anything I can to get a few extra weeks in to grow.


The way I made my cold frame is I used three six-foot long half-inch PVC pipe, plumber’s tape (or something you can secure the pipe down with, such as a metal two-hole strap), plastic sheeting and screws. I used a drill to screw in six pieces of plumber’s tape along the outside of the raised beds equally spaced with three on each side of the long edge of the bed. I formed a “U” big enough to hold the pipe down securely along the side of the bed. I then inserted a PVC pipe on one end on the “U”, bent the pipe and inserted the other end into the opposite “U”. This created an arch of PVC pipe. I repeated this twice more with the other four “U” points to create a frame. This allows me to pull a large plastic sheet over the bed, large enough to cover all edges of the bed. I tie the ends of the sheet on both ends to create my mini green house. I have seen so many other ways of creating a cold frame including hay bales and old windowpanes. Just use what you have!


Once it really heats up, closer to summer, I take off the plastic sheeting to prevent the plants from overheating. As the end of the growing season nears, I place the sheeting back over the plants to extend the season just a few more weeks and allow the plants to continue growing and to protect my harvest.


The cold frame allows me to get some plants growing just a little bit sooner. Some of the first things I will put out under the frame will be cold-tolerant seedlings early to mid-April such as broccoli, kale, beets, lettuce, and cabbage. By covering my raised bed and creating a temporary cold frame, I can extend my season just a little bit more and enjoy home-grown vegetables that much quicker.



Caption: A cold frame is a great way to extend your growing season! Here is a temporary cold frame I created with PVC pipe. I cover the PVC pipe frame with plastic sheeting to allow heat to be trapped inside, creating a mini greenhouse for my vegetable plants.

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