Winter can be both a welcomed reprieve from gardening chores, or a season of dread for the home gardener. If you fall into the latter category, have hope as you can actually grow lettuce in winter and keep your garden growing a little longer.
You may have heard of using hydroponics and artificial lights to grow vegetables, such as in your basement, but I have a tactic to share that will cost less money and won’t be nearly as time intensive. I’ll share exactly how to do this.
Lettuce in Winter
Can You Grow Winter Lettuce?
Some years I’ve been able to grow winter greens with hardly any effort. The secret to growing lettuce in winter -outdoors – is to use a cold frame box. Today I’ll explain what a cold frame box is, how we made one and show you photos of green lettuce growing and ready to be harvested!
For a little background I am located in Northern Ohio and traditionally our zone is 5B although in recent years it has warmed up a bit. We have four seasons, and a true winter with frost and then inevitably snow. My winter lettuce growing experience will pertain to my climate.
However, if you live in a colder climate you can still try to grow lettuce all winter. Alternately, if you live in a slightly warmer climate you may find even greater growing success.
Lettuce Growing Season
Like most home gardeners who live in an area with a true winter, I originally thought my gardening and gardening updates would end around November. The last thing I imagined was having a report on my garden in December, or January.
If you live in the Midwest, by the time we reach January it’s usually 20-degrees out, there is a frosting of snow and even our rescue dog Lulu is complaining about going outside to do her business. But, as it turns out you can continue to garden into the winter and grow lettuce in winter.
A few years ago, toward the end of the typical growing season, my husband finished building us a cold frame box. I tried to find the directions we used but he did modify them quite a bit in order for us to garden. There are many ways you can build a cold frame box but I’ll share the basics.
Cold Frame Box Lettuce
What is a Cold Frame Box?
A cold frame is an enclosed box with a lid that stays outdoors all winter. The lid is usually clear so sunlight can still enter the box (like a window) and help plants grow. Most often gardeners will grow lettuce in the box during the winter.
A photo of our box is shown above and as you can see on that day there was snow covering the box. You can still see the outline of the clear panes, the handle to open the box and the small white vent on the back for air flow.
If you search for “cold frame box” online you will find a variety of resources, pictures and plans. Here’s one tutorial on how to build one with an old glass window. My husband made ours from scratch using the following supplies:
- cedar wood (we chose cedar as it’s more resistant to pests)
- metal hinges
- cabinet handle
- vent for air flow
- plexiglass panels (we used four, or try clear polycarbonate roof panels)
- boiled linseed oil and disposable brush (optional to condition wood)
Our cold frame box measures about 4 feet by 4 feet and at its height it’s about two feet tall. There is a slight angle to the box to allow for additional light to come into the box. He used a miter saw to cut the wood and a handheld drill to assemble the box.
Then we placed it outside on level ground. He then installed the lid. It is best to place your box south-facing if possible for the most sunlight in the winter. Also be sure to condition or amend the soil inside the box if it’s a brand new planting area.
Many winter gardening box plans call for using an old window or glass door for the lid. You might be able to find one of these on the side of the road on trash day or purchase one by visiting a Habitat for Humanity ReStore location.
Other ideas include asking friends or family, looking on Facebook Marketplace or visiting local flea markets. Many plans also suggest making your cold frame about the size of a door, if using a glass door. This seemed a bit large for our needs and space, we used the four plexiglass panels and our box is closer in size to a window.
Ours is more of a square shape, but probably equally large. The truth is your cold frame box can be as large or as small as you want it. The cold frame box also doesn’t not have to be air tight and you don’t want it to be in order to allow some air flow for the plants.
Don’t overthink building your box. If this is your first box start small and if you enjoy learning how to grow lettuce in winter then you might expand the size of your box in the future or add a second box.
What to Grow in Winter?
The box has allowed us to grow lettuce year round. The year I took some of these photos had an abundance of lettuce in my box I used Romaine Lettuce which is known to grow well in colder temperatures.
Even though the lid helps insulate the box you need to keep in mind the ground is still cold underneath. This year I have planted in my cold frame box:
- green onions
Any crops you try to overwinter need to be frost tolerant or frost hardy. The box acts as a small insulated chamber and keeps the interior temperature warmer than it is outside. This allows plants to continue to grow.
How a Cold Frame Works
The sun hits the angled lid and it produces heat inside the box to keep crops growing well past the normal gardening season. A cold frame is especially helpful for those in regions where winter hits hard – ie. Cleveland. The cold frame box actually works much like the milk jug greenhouses I make every year.
Normally gardening season is wrapping up in October. But these photos were taken on December 10 when I was still picking fresh lettuce outside. Deer and other critters such as rabbits cannot get in the box. Without animal predators your chances of success at growing a garden in the winter are much higher!
Planting and Growing Tips
First you need to build your box and install it in your yard. After that you need to plant your lettuce. When I grew lettuce in the cold frame I planted the lettuce seeds right after putting my garden to bed. Usually the seed packet will explain how late in the fall season you can plant.
Typically you will need to plant before the risk of a fall frost. This allows the seeds to sprout and gain some size and strength before the frost. While the box will protect the plants, again remember you need to still be planting frost tolerant or frost hardy plants.
If you are trying to plant later in the season, look for varieties that mature quickly, some greens mature in as little as 28-days. These frost dates and warnings will vary depending on where you live and also if it’s a cold winter or mild winter.
Some years we have had 50-degree days into December! This is not normal but has helped my lettuce grow even longer. This year I opted to plant my fall crops early, however. You can plant the seeds as early as August.
Winter Lettuce Growing
As your plants grow you will need to closely monitor their growth and the weather. This will require you to frequently water and ventilate your cold frame (open the lid on warm days, close the lid on cool days/nights). Because of this I would recommend planting more around October or early November.
Overnight temperatures will be more mild and the winter greens won’t require as much care or attention. Pick any variety, although I would suggest a variety that germinates and matures quickly, such as in 30 days to 45 days, just in case winter is especially harsh.
Check the back of the seed packet for this information. I recommend Botanical Interests as a great company to purchase organic and heirloom seeds from. Their seed packets are not only beautifully designed, but also loaded with information.
Grow Lettuce in Winter
Growing Lettuce Winter
Above you will see a photo of my lettuce once it sprouted. Please keep in mind that a cold frame box will allow you to keep growing but depending on how harsh the winter is, the lettuce may not grow all winter. Personally, I have had success into January.
If winter is mild and you harvest the lettuce frequently the cold frame box could keep your lettuce alive until spring. If it’s a harsh winter (such as it was the year we made the cold frame box) my lettuce stayed alive until mid-January. It will also depend on how attentive you are to your box and crop.
Growing Lettuce in the Winter
If possible, the cold frame box should be placed facing south. The way a cold frame works is it’s like a miniature greenhouse. I have included a few photos so you can see what the cold frame box looks like inside. I planted a mixed lettuce packet that year.
You can plant arugula lettuce, Bibb lettuce, kale, spinach or other varieties. You could also experiment with other cold weather crops such as radish, although I have not personally tried this myself yet. I also wonder if some herbs would grow in the cold frame? My parsley (which is normally an annual) overwintered until January last year.
More Lettuce Growing Tips
The best part about having a cold frame box is you can use the box year-round in your garden. When spring hits simply remove any remaining lettuce, turn the soil and fertilize the bed (use my end of season tips) and plant something new.
Depending on how you construct the cold frame box, you might remove the lid or simply prop it up during the summer growing season. You also may open or close the (optional) air vent depending on the weather. Really a cold frame works just like a raised garden bed in the off-season.
Once installed, unless something breaks on the cold frame box it will require minimal maintenance and should last for several years. You can opt to lubricate the hinges with WD-40 if they are squeaky or begin to stick. I also recommend applying boiled linseed oil to the wood at least once every year to preserve and protect the wood.
Growing Lettuce in Winter
If we had finished the frame sooner the first year I would have planted some broccoli in there too. My advice would be to start your cold frame project in late summer to make sure you have time to plant your first crop. If it’s too late for this season, build a cold frame box in the off season and use it next year.
Remember, a cold frame box can be as large or small as you like. It can be complicated or simple to make. If you opt to place the cold frame near your home it will also be easy to harvest. You may only need to take a few steps outside to pick your crop.
This year I decided to harvest the last of my lettuce in early December. I have a busy month and do not want to tend to the cold frame, however, in other years I have kept the crop going even longer!
What cold frame questions do you have?
*This post was originally published in 2013 and has been updated and republished for accuracy and comprehensiveness.