Winter Gardening in a Cold Frame

A cold frame is exactly what it sounds like: a clear outdoor frame that protects plants from cold weather, while still letting sunlight in. Providing a warm and protected space in your garden for spring seeds will allow you to get a head start on your gardening season. Cold frames, usually made of lumber or hay bales and old windows or glass shower doors, are the perfect way to control the climate in your nursery beds. Not only are they very easy to make and use, but a well-constructed cold frame can last you for several years to come.

DIY Your Cold Frame

To start your winter gardening plans strong, consider constructing your own cold frame at home. First, determine the best spot on your land to put it so you can set yourself up for a successful spring harvest. Look for a site that offers full sunshine and shelter from prevailing winds, and face the frame towards the south. You can place it against a house, deck, shed, garage, greenhouse, or allow it to stand free in the garden.

Once you’ve found an ideal place, you can start constructing the elements of your homemade cold frame. The frame, as mentioned earlier, is typically made from wood, but working with other materials on hand, like blocks or bricks, is perfectly fine. The clear lid lets in the sunlight, trapping warm air inside while protecting plants from inclement weather.

For the lid, salvaged windows will do the trick. But, not all of us have those readily on hand, so purchasing plexiglass, a sheet of glass, or twinwall polycarbonate will work too. Slope the lid towards the midday sun for maximum light and warmth. Position your cold frame directly onto the soil or on concrete or slabs.

Braving the Winter Chill

Now that you have your cold frame constructed, it’s time to get gardening. In some northern climates, winter temperatures can fall as low as 5°F, which will kill unprotected herbs, vegetables, and fruits – even hardier greens like arugula and mizuna. Luckily, your cold frame will ensure the plants’ survival by insulating them from the ice, snow, and extreme temperature drops. Typically, plants that are pulled through the winter in cold frames grow/bloom fast first thing in the spring.

Because winter is the harshest growing season, we recommend planting the hardiest plant options you can find. Generally, this would include salad greens, like arugula, spinach, mache, and lettuces. When you plant your seeds in the frame, you may notice that they barely have time to germinate before their growth slows to a crawl due to the shorter, limited-sunlight days of winter. But, don’t worry – the show really plays out in March, when the protected seedlings burst into robust plants for a successful harvest.