Happy Autumn! The days are getting shorter and colder and many gardeners are starting to tidy up their gardens in preparation for winter. If you have a cold frame, however, you can extend your season with cool-weather crops, protecting them from frost in their own little mini-greenhouse bubble.
The ideal time to prepare for growing in cold frames is August, because you can make a space in your garden, set it up, and sow some seeds before the temperatures start dropping. It’s not too late for baby greens, though! And there are some very cold-hardy greens that are a bit unusual but definitely deserve a chance if you’re interested in growing during cold weather.
A cold frame can protect plants from frost and colder temperatures so you can continue to eat from your garden, sometimes even when there’s snow on the ground. In fact, I read a book recently by Niki Jabbour, The Year-Round Vegetable Gardener, that explains how to grow your own food 365 days a year! The author lives in Nova Scotia, Canada, where it snows and gets really cold in the winter, so she makes good use of cold frames. Her book is my main information source for this post. I recommend reading it if you are interested in extending your growing season.
Cold frames can be used in spring as well, to get a head start on the growing season. Many cool weather crops thrive in a cold frame before the garden is even ready for the tomatoes. That’s a topic for another post, though.
How to Build a Cold Frame
A few years ago I came into a pile of old windows, and hubby build me some frames that fit the windows. They were triangular cold frames, built so the windows rested on the frames. The windows could be propped open with stakes, or I could slide them across the frames so they were partially open. When the temperatures were nice I could take the windows right off and lean them against the end of the frame. You can see these frames in the photo above.
There are lots of plans online for building cold frames, so I won’t go into too much detail here. You’ll need to figure out what works for you. Some people use straw bales and put windows on top. Super easy, no carpentry skills required!! Others use plastic instead of glass, and pvc tubing instead of wood. It’s really about personal preference. I’m more interested in what to grow in the cold frame, so I’ll let you research the building for now. If you find any good plans, let me know and we can share them with everyone else.
Here’s an example of cold frame plans: http://www.almanac.com/content/cold-frames-gardening
What Can be Planted in a Cold Frame
Due to the cooler temperatures and less available sunlight, fruiting plants will not do very well in a cold frame. So you’re basically looking at greens and more greens for your fall salads. Since it’s nearing the end of September, options are further limited. Next year we’ll need to start thinking about this in July, prepare/plant stuff in August, then harvest in the fall and winter for the crops that are more ‘cool’ weather instead of ‘cold’ weather. The following are the hardiest and will handle the colder temperatures if they’re planted right now.
Arugula can be planted now, and if you keep it in a cold frame you’ll still be eating it when there’s snow on the ground. If you like a milder flavour, though, you should plant a few batches. As the plant gets older the leaves get more bitter.
Claytonia can also be planted at this time. It’s a green that is similar to spinach in flavour, and grows best in cool weather. When it flowers, you can eat the flowers and leaves together without any noticeable decrease in flavour.
If you like baby Kale, you can sow that in a cold frame right now too. The young tender leaves are great for salads, as I discovered once when a friend brought a salad that was made more of kale than lettuce! It tasted fantastic.
Mache, or corn salad, can be sown in a cold frame every 2 weeks until mid-October! It’s a good way to get fresh greens in winter. It will stay alive throughout the cold season with some protection.
General Guidelines for Growing in a Cold Frame
1. Don’t fry your plants. This may seem like a silly guideline, but it’s not. The cold frame will get really hot if the day is sunny. You might need to prop it open just a crack, to allow extra heat to escape, even on a cold day. So keep an eye on your plants, especially when it’s sunny outside.
2. For additional warmth at night, you can cover the frame with a foil blanket (one of those emergency blankets) and/or an old comforter.
3. Don’t expect vigorous growth when the weather is cool. Things will not grow as fast as they do in the summer due to less available sunlight and colder temperatures at night.
Thank you to Susan for suggesting this topic. I’m open to suggestions for other topics, so please use the contact form or facebook group to let me know if you have any other requests!