The crispness of the air is a signal that gardening season is coming to a close. Some plants thrive in hot weather such as tomatoes and peppers while others falter when hotter weather is present. These cool season plants or cole crops include kale, lettuces, spinach, peas, cauliflower, and broccoli to name a few. Typically the cooler the temperature the better these cole crops like it but…Freezing temperatures can be the down fall for these plants. The solution to this temperature dilemma and the never-ending question of how to extend the growing season is the use of a cold frame greenhouse.
How a cold frame works is very similar to how a greenhouse works. Both utilize solar radiation to create heat in an enclosed space. But unlike a greenhouse a cold frame can utilize soil temperature along with solar radiation to keep things warm. And temperature can be regulated by simply opening up the window during the day and closing at night.
There are generally 3 types of cold frames. The first type is one that is moved to the garden site to cover the cole crops or the cold frame remains stationary and is planted directly into. This type of cold frame is perfect for cole crops and to start and harden-off seedlings.
The second type utilizes soil temperature, solar energy and mulch to keep this type of microclimate warm. This cole frame requires a pit to be dug and cinder blocks to line the walls. Then straw and mulch is place around plants in pots to fill in gaps. The cold frame is then placed on top. Remember to use an opaque cover because the goal of this type of cold frame is to just maintain these plants while they are dormant. This type of cold frame is great for tender perennials, tropical vegetation, and tall plants.
The third type of cold frame is also known as a hot bed. This type of cold frame utilizes heat generated from straw and green manure plus solar radiation and heating cables to keep the garden area warm. Hot beds are great for areas in the country that receives a lot of cold weather and snow but remember to knock the snow off the glass in this type of environment. This type of cold frame can be used to grow cole crops but also as a way of protecting tender plant material during the dormant period. Cold frames/hot beds are a great addition to add to any gardener’s arsenal in the quest for year-round, homegrown vegetables. And it also ties in simply with a small carbon footprint while keeping up with a locavore lifestyle.
So when Old Man Winter’s breath blows in smile and enjoy a crisp, green salad grown with one’s own hands. And remember that this simple technology can be used in a traditional garden, square-foot garden, rooftop garden, and even on the apartment homestead.
ABOUT THE AUTHOR
Mindy McIntosh-Shetter has been an Agricultural Science educator, and is a horticulture and/or environmental blogger who earned a degree from Purdue University in Agriculture Education with a minor in biology, and natural resources. Presently she is finishing up her Masters in Environmental Education and Urban Planning for the University of Louisville while working on her own agriculture/environmental blog.