Did you know that you could grow a wide variety of fresh vegetables outside, no matter how cold it gets? All you need are some basic DIY skills to build a cold frame that houses your fave veggies year-round. We asked SavvyGardening’s Tara Nolan, author of Raised Bed Revolution: Build It, Fill It, Plant It…Garden Anywhere! for her best tips.
How does a cold frame work?
A cold frame is essentially a raised bed with a clear lid that traps the warmth of the sun inside, allowing you to extend the growing season (or get a head start on it).
Can you use recycled materials to build one?
I build all of my raised beds with untreated, rot-resistant cedar. You can inquire at your lumberyard or big box store what’s more readily available in your area. I don’t recommend using pressure-treated wood to grow edibles, as you don’t know what could leach into the soil.
How complex is this project?
For my project, I found recommendations to raise the back of the cold frame up three to six inches to help capture the winter sun’s rays, so there was some measuring and math involved. I’ll be honest: I had my carpenter brother-in-law help me with the design. If you’re just building a lid for an existing raised bed, you’re just adding hinges. Also, you’ll want to dig the raised bed into the ground a bit.
When and how should you start planting?
If you’re growing greens, you can plant them pretty close together. The great thing about a cold frame is you can plant in late winter for spring crops and late summer/early fall for a winter harvest. If there is nothing occupying the cold frame over the winter, I like to have the soil ready to go in late fall, so I can pop things in as soon as the ground thaws a bit. Be mindful of frost dates in your area, but don’t be afraid to experiment! Also, you might want to start some plants inside under lights before transferring them to the cold frame.
I think it’s pretty cool harvesting any edible when it’s freezing outside—kale and spinach are favourites. Root veggies, like beets and carrots, will also do well. And I always leave some leeks in the ground for winter soups.
Where you should place your cold frame, and what kind of maintenance does it need during the winter?
For placement, be sure your cold frame faces the sun, so it can capture as much solar energy as possible.
As cold as it might be outside, it can get mighty hot inside your cold frame, so you want to make sure that you check on it and vent it. Otherwise, your veggies will cook instead of grow! An indoor/outdoor thermometer is a great tool to have inside the cold frame, as it will indicate the temperature. You don’t want temperatures to rise above 15°C. You can just use a stake to prop it open, but a friend of mine has an automatic opener with a special sensor that will push the top up when the temperatures rise. I need to get one of those!
Also, if there’s a big snowstorm, you’re going to want to clear off the top. And I will caution that if you’re using an old window, they can be very brittle and break easily. Be careful when opening and closing it. Year-round veggie gardener Niki Jabbour uses Lexan twinwall polycarbonate for her cold frames.
Tell us what you’re going to plant this winter!
PHOTO CREDIT INFORMATION:
All photography by Donna Griffith for Raised Bed Revolution.