Winter can be both a welcomed reprieve from gardening chores, or a season of dread for the home gardener. If you are the latter, 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 an idea to share that will cost less money and won’t be nearly as time intensive. To be honest – 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!
Lettuce in Winter
Why Most People Don’t Grow Winter Lettuce
Like most home gardeners, 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, around this time it’s usually 20-degrees out, there is a frosting of snow and even our 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 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 grow lettuce in winter. There are many ways you can build a cold frame box but I’ll share the basics.
What is a Cold Frame Box?
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. He made ours from scratch using:
- cedar wood (we chose cedar as it’s more resistant to pests)
- a few metal hinges
- a small cabinet handle
- a vent for air flow
- some plexiglass panels (we used four)
The box is allowing us to grow lettuce in winter. Our cold frame box measures about 4 feet by 4 feet and at it’s height it’s about two feet tall. Many plans call for using an old window or glass door for the lid. Many plans also suggest making your cold frame about the size of a door. (we used four)
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. Don’t overthink building your box. This project can be as easy or as complicated as you like!
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Next Steps After Your Cold Frame is Built
When I grew lettuce in the cold frame I planted the lettuce seeds right after putting my garden to bed. You could plant the seeds as early as August, however, it will still be rather warm out. This will require you to frequently water and ventilate your cold frame.
Because of this I would recommend planting more around October or early November. Overnight temperatures will be more mild and the lettuce in winter 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.
Grow Lettuce in Winter
Their seed packets are not only beautifully designed, but also loaded with information. Please keep in mind that a cold frame box will allow you to grow lettuce in winter but depending on how harsh the winter is, the lettuce may not grow all winter.
If winter is mild and you harvest the lettuce frequently the cold frame box could literally 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.
Here’s What Lettuce in December Looks Like
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?
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. There’s another reason why I like the cold frame, too. 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!
Use a Cold Frame Box Year-Round
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.
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.