Article published in the News-Review on November 29, 2024

By: Mackenzi Hall

COLD FRAMES: Extend Your Gardening Season

Question: I generally only keep a garden during the summer months, however a friend recommended I look into building a cold frame, so that I can extend my harvest into the fall and winter. I have heard the term before, but do they actually work and is it easy enough for me to build at home?

Answer: For gardeners eager to extend their growing season or get a head start on spring planting, cold frames offer an excellent solution. These simple structures create an environment for plants that protects them from the torrential rain, snow and freezing temperatures we can experience here in a Douglas County winter. 

Starting with the basics, a cold frame is a mostly transparent structure, usually made with a wooden frame and a glass or plastic lid. You can upcycle an old window for the topper or even use a hay bale with the center cut out for the frame. This is your chance to be creative! The see-through lid is required, though, as it utilizes the sun’s solar energy to warm the soil and air inside. Essentially it acts as a mini greenhouse, trapping heat and creating a microclimate that allows plants to thrive despite chilly outside temperatures. If you feel the need, you can add hinges to attach your lid to the frame. It isn’t completely necessary, but it can make checking in on your plants and propping open your lid easier. Once your cold frame is built, you will want to place it in a location that receives at least 6 hours of sunlight. It’s possible that this location will change throughout the season, so consider using materials that are light enough to easily pick up and rotate. 

Once the harsh weather hits, here are a few things you will want to consider: In rainy/wet conditions make sure you are using well-draining soil in order to prevent water-logging your plant’s root systems. If snow accumulates on the top of your frame, you’ll want to be sure to sweep it off. If you don’t, it can cause the microclimate you have created to become too cold and too dark for your plants to grow. When it is especially cold outside (below freezing temperatures for multiple days in a row) you may want to consider wrapping your frame in a blanket or row cover at night to protect delicate foliage. On the other hand, Douglas County is also known for having a few warmer winter days. If this happens, prop the lid open to allow for plenty of ventilation and to keep your plants from overheating. Also a good idea to place a thermometer inside the cold frame to make sure things aren’t getting too warm during sunny spells.

For gardeners who start their own seeds, cold frames provide an ideal environment for young plants, shielding them from harsh winds and sudden temperature changes. This works the same for more established plants in the winter. Winter greens, such as kale, spinach, and collard greens can thrive in a properly placed cold frame even when the rest of the garden is taking a much needed “nap”.

Cold frames are an invaluable tool for extending your gardening season, allowing you to grow fresh produce even in the chill of winter months. Their simplicity and effectiveness make them an excellent investment for any gardener looking to enhance their skills and enjoy the fruits of their labor year-round. By building and utilizing a cold frame, you’ll not only get the chance to cultivate a wider variety of plants, but also experience the joy of gardening no matter the season.

Do you have a gardening or insect question? Contact the Douglas County Master Gardeners at douglasmg@oregonstate.edu or 541-672-4461 or visit 1134 SE Douglas Ave., Roseburg. Douglas County Master Gardeners are trained volunteers who help the OSU Extension Service serve the people of Douglas County.