Grow Food Outdoors All Year Long With Cold Frame Gardening
As cold and snowy weather descends upon us here in the Northeast, I find my achy joints actively calling out for more attention. Living with arthritis as a gardener, I have formed a close bond with the land in order to better support my body. My immune system requires careful tending, and I find myself craving dark leafy greens, hearty soups and protein rich comfort foods as the weather turns cold. But in a cruel twist of fate, when my body craves these deeply nutritious foods most, the bitter cold of our New England winters do not accommodate a growing season which would allow me to cultivate all of the produce I wish to grow deep in December.
So how do we ask the land to sustain us through its deep hibernation? The answer may be found in the form of a simple wooden box called a cold frame.
This rustic frame set into the earth, snuggled up against the sunny south wall of our home provides us ample opportunities to tend, grow and gather even in the darkest days of winter. It can feel like pure magic to enjoy a diverse variety of produce even as we are cozy in our blankets beside the fire.
How does a cold frame work?
A cold frame works by creating something like a mini-greenhouse, trapping warm air through solarization inside of the box and insulating the plants within from the worst that winter has to offer. We control the temperature inside of the cold frame with a simple vent - the hinged lid can be propped open with different sized sticks to allow excess heat to escape on warmer days, but for the most part in our deep New England winters the lid stays firmly shut until we trudge through the knee deep snow to harvest.
Like many things in life, we cannot expect to circumvent nature entirely for our own benefit. Nothing in nature blooms all year. Try to plant delicate heat loving peppers, for example, and you will be met with disappointment. Similarly, the plants enjoy a slower season in winter, much the way we humans do. If you’re not convinced, I’d ask you to consider this: if the trees can take a break, so can you.
A cold frame is a lesson in slowing down and radically accepting things as they are. Your kale, radishes and lettuce will grow and thrive at a slower pace than you can expect in warmer seasons. The harvests are fewer, but more rewarding for the mere fact that they exist at all. And while a cold frame requires a certain amount of upkeep and planning in the beginning, this slowed down nature means that watering and weeding becomes virtually unnecessary in the coldest months.
Now, if you live in a climate that does not experience a cold winter season you may think a cold frame is unnecessary. Although, they continue to be useful even into the spring season here in New England since they make the perfect protected nursery in which to harden off your summer seedlings each spring. And if you can easily build one for cheap or free using reclaimed materials, why not give it a try?
Where should you put a cold frame?
You’ll want to choose a location for your cold frame that is protected from north winds and generally sunny. This means the best spot for your cold frame will have no shade from any trees, and preferably be placed with the back wall of the cold frame up against the south side of your house, shed or barn. If you don’t have a spot like this available, then anywhere without shade will do. You’ll just need to spend some extra effort properly insulating your box from the winds.
Speaking of howling winds, so long as it is protected from those north winds we discussed you shouldn’t worry yourself too much about creating something airtight. Your cold frame is not a greenhouse, and so we don’t expect it to function quite the same. Build your frame to be thick and sturdy, but don’t worry about every little seam and crack.
How to build a cold frame
If you have the time and physical ability, building a cold frame yourself is absolutely the most economical solution. Purchasing one ready-made can cost you anywhere from $60-$500 and quality issues on the low end of that budget will prevent you from getting many years of use out of it. Meanwhile, if you build one yourself it can be done for far less than the low end of that range and produce an end result that will be sturdy enough to continue providing shelter to your winter crop for years to come. While old windows can be fragile and prone to breaking, when they can be found for free I still find it a better option than a new piece of corrugated plexiglass.
We built our cold frame just as the first leaves began dusting the earth, making their final descent from the branches above. Pulling out the old wooden windows and reclaimed lumber from our basement, I didn’t really have a plan. This is the nature of projects on our little homestead - in order to put to rest my fears and limiting beliefs, I have a tendency to turn a blind eye to the specifics and figure things out as I go. “I’m just going to build a big rectangle, the size of the two windows combined, and stick the windows on top” I confidently told myself. It’s safe to say I don’t have a ton of confidence when it comes to building things, but I was betting that between the two of us, we could figure it out. A chill wind traveled across the field. I adjusted my hat over my cold ears and set to work.
This method of trial and error has generally served me quite well on this journey, and I’ve found it to be essential to growing plants in particular. A fussy Nasturtium in Georgia, for example, is going to have very different needs that one planted in Vermont. So why overwhelm ourselves with tips and tricks from every gardener in the land when we could simply plant, observe, expect failure and experiment until things go right?
You can use many different materials to build a cold frame - but the very best materials are the ones you already have. Our little pile of scrap lumber provided nearly everything we needed to create a sloped box on which to mount our hinges and old wooden windows.
The result was…lopsided. For some reason, the box wasn’t sitting level on the earth, the wood having twisted under tension at some point, unnoticed by our novice eyes. The old windows we used for a lid were chipping questionably safe paint flakes every time we opened and closed the hinges. But it was finished, and it was free, and so - in the ground it went. I packed straw around the exterior to fill in the gaps where the frame didn’t meet the soil and added extra in the space between the wall and the cold frame, set my plants in the earth and held my breath that I would discover an abundance of fresh food beneath the glass in a couple of months.
I suppose I shouldn’t have led with such an obvious spoiler, but the cold frame did work, and an abundance we did have, regardless of our lack of building skills. And so as its lessons compounded the cold frame became something more than a simple box to grow in. The weathered wood shines like a beacon, a reminder to ourselves that we can accomplish more than we think, and done is better than perfect.
What Can you grow in a cold frame?
Kale
Swiss Chard
Spinach
Radishes
Lettuce
Beets
Carrots
Arugula
Kohlrabi
Scallions
Parsley
Mustard
Best cold frames to buy
Don’t want to build your own cold frame? There are many pre-made options available that are built to last. I suggest looking for a cold frame that has a rot-resistant cedar base and shatterproof polycarbonate lid. If you already have raised beds, then a plant protection tent may be the best option for you as you can simply convert your raised beds into a cold frame for the winter months and then remove the tent structure in the summer heat. Here’s my recommendations for the best pre-made cold frames and tent frames you can buy:
The 3-Season Garden Protection Tent from Gardener’s Supply makes it easy to access plants within your raised bed and includes two covers and durable powder-coated steel frame. This tent provides 70% light transmission, 40" of head room at the peak, and has roll-up end windows for ventilation. A second cover protects against ravenous summer bugs and scorching sun. Three zippered doors on each cover provide easy access for tending and harvesting. Tie-downs secure the covers to the steel frame. Click to Shop
The Cedar Cold Frame from Gardener’s Supply is an attractive cold frame with a narrow footprint. The base is made from rot-resistant lumber with aluminum corners. The top is made with polycarbonate panels that diffuse light so plants don't "cook," and there are adjustable braces to hold panels at various intervals for ventilation. Click to Shop
