Greenhouse Gardening In Winter – the Best Vegetables for Winter Growing!
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It is common to see greenhouses left sad and empty in winter, but why leave them empty when you could be growing a winter garden full of delicious veggies and herbs? The colder months are the perfect time to move your garden indoors to a greenhouse garden!
Gardening in your greenhouse in winter is simple if you know about the best plants to grow, such as peas, radishes, cabbage, herbs, and lettuce. Think about it – when the worst of the winter weather hits, your greenhouse will provide shelter and protection for your plants!
In this article, we’ll go over some of our favorite tips and tricks for over-winter gardening in a greenhouse. We’ll also discuss the best plants to grow in a winter greenhouse and how to keep your greenhouse warm during the colder months.
Table Of Contents
Can You Grow Plants In a Greenhouse In the Winter?
You can grow many plants in a greenhouse in winter, including some cold-tolerant and hardy vegetables and herbs. Whether you have rain, hail, snow, or icy winds, your greenhouse will stay dry and draught-free.
A greenhouse is a multifunctional and versatile year-round growing space. Some of the benefits of having one include:
- A greenhouse will maintain warmer temperatures in the summer so that you can grow vegetables better suited to hotter climates.
- Greenhouses also help to extend your growing season by giving you a warmer growing space in the spring and fall.
- In the winter, a greenhouse gives you a perfect little microclimate to keep plants sheltered from the worst of the winter weather!
And if you are lucky enough to get some summer sun, the temperature inside the greenhouse will quickly heat up too!
So, if you’re considering whether a greenhouse is worthwhile, we’d say it is! And using it all year round means it will pay for itself even more quickly.
Do Greenhouses Stay Warm In the Winter?
Greenhouses do not stay warm in the winter without insulation or a heater. The daytime sunshine offers a few hours of warmer temperatures. But, overnight, the greenhouse will be almost as cold as the external air.
These dropping temperatures mean that if you live in a zone prone to temperatures below freezing, you will not be able to grow plants that are sensitive to frost in the winter in a greenhouse.
I know this from experience, as our first frosts here have just finished the last few summer-fruiting cucumber plants in our greenhouse!
Growing summer fruiting vegetables in the winter requires considerable skill and investment – we’re talking heated greenhouses, grow lights, and controlled ventilation here!
To start with, we’d suggest starting with more straightforward suggestions for vegetables that will grow happily through the winter in the greenhouse.
If you are contemplating using your greenhouse to grow vegetables in winter, it is worth planning what you want to grow.
So, let’s discuss which vegetables work well in a winter greenhouse garden.
Read More – What Should You Plant in December in the USA?
Best Vegetables to Grow In a Greenhouse In Winter
A greenhouse is ideal for growing vegetables over the winter! So, don’t let this valuable space stand idle, and fill it with cold-tolerant vegetables.
Growing vegetables in the greenhouse over winter is a great way to nurture plants outside of their regular growing season. It is also the best time for growing vegetables that bolt (go to seed) in hot summer weather! Such crops include my favorites, like salad rocket and pak choi.
There are two groups of vegetables you can think about growing in a greenhouse over winter.
The first of these are vegetables that would not tolerate harsh winter conditions. These may be plants that prefer warmer daytime temperatures or those that will be simply miserable if exposed to cold winds.
The second group is winter greenhouse vegetables that grow happily outside in the coldest weather. These are the cold-hardy vegetables that grow naturally during cold winters in Northern climates.
However, growing them in the greenhouse will speed up the growth and yield bigger harvests. They will also have protection from pests and harsh weather in the greenhouse.
These are some of my favorite winter vegetables to grow in a greenhouse:
1. Peas
Peas are an excellent winter greenhouse crop! Yes, peas will grow happily in a greenhouse in the winter. Peas are markedly cold-hardy to twenty degrees Fahrenheit and can flourish when temperatures exceed 40 degrees. They may not crop until early spring, but you will be rewarded with deliciously tender green peas long before the outdoor crop is ready.
For bonus points, try Tom Thumb Peas. They’re famous for being more cold-hardy than other pea cultivars.
2. Salad Greens
Winter salad greens rule! My favorites are salad rocket, endives, Mizuna, land cress, claytonia, and purslane. But my top choice greenhouse salad green is lettuce. Lettuce grows best at around 55 to 65 degrees Fahrenheit, which many winter greenhouses can achieve. Lettuce can also survive temperatures as low as 35 to 40 degrees Fahrenheit, but they will not survive hard frosts.
3. Celery
Celery is an excellent garden crop that grows like a charm in a sunlit winter greenhouse. Celery plants can flourish with nighttime temperatures of 50 degrees Fahrenheit and 60 degrees during the day. They only require around six hours of daily sunlight, which is manageable, even in winter.
4. Leafy Greens
Leafy greens like spinach, kale, Swiss chard, and beetroot are superb additions to your winter greenhouse. Spinach is arguably the best, as it can happily prosper in your greenhouse with four to six sunlight hours and temperatures between 45 and 68 degrees Fahrenheit. We know spinach isn’t the most exciting garden crop. But it’s easy to grow and makes tremendously healthy smoothies, salads, soups, and veggie stir-fries.
5. Radishes
Radishes are another underrated cold-weather crop that can flourish at 40 to 70 degrees Fahrenheit. The only trick to growing winter greenhouse radishes is sunlight. They prefer eight to ten hours of daily light. However, they can survive with as few as six daily hours. (Inexpensive LED grow lights can also give them a boost!)
6. Brassicas
Brassicas, such as cabbages, broccoli, and Brussels sprouts, are some of the most underrated winter greenhouse crops. Brussels sprouts are especially fitting for cold-weather growing. They flourish when temperatures are 65 degrees Fahrenheit or lower. And they can thrive with as little as six or seven hours of daily sunlight.
7. Alliums
Alliums, including garlic, leeks, onions, scallions, and spring onions, will grow cozily and happily in your winter greenhouse. Leeks and garlic are our two favorite alliums for winter greenhouses. Garlic, especially, is tailor-made for winter growing, as it requires cool temperatures when it first starts developing. Fifty degrees Fahrenheit works perfectly.
8. Annual Herbs
Annual herbs like coriander, dill, chervil, and parsley are lovely crops that can work in a greenhouse or a sunny windowsill. Of these crops, dill is my favorite for wintertime growing. Dill is excellent because it’s ludicrously winter-hardy and can survive overnight temperatures as low as 20 degrees Fahrenheit. (But, it likes 65-degree weather better.)
9. Oriental Greens
Oriental greens, such as mustard leaves or pak choi, are two more to add to your winter-hardy and greenhouse-friendly list. I’m a massive fan of mustard leaf, as it’s a little-known crop with at least a dozen delicious cultivars worth trying. The mustard leaf can also sustain chilly weather. Even overnight temperatures as low as 32 degrees Fahrenheit won’t kill the plant.
Try growing spicy Kodiac mustard leaves or Mizuna for intense flavor and fresh garden salad. Osaka Purple is another fun variety if you want some brilliant shades of violet in your winter garden.
10. Root Crops
We saved the best winter-hardy greenhouse crops for last. Root crops! We’re talking about carrots, beets, turnips, potatoes, and celeriac. Any root crop can flourish mightily in a greenhouse. But potatoes are my favorite because they are versatile in the kitchen!
The only downside of growing potatoes in your winter greenhouse is that they like warmer temperatures than other crops on our list. Potatoes love growing between 65 to 80 degrees Fahrenheit during daytime and as low as 55 degrees at night.
We recommend the Year-Round Vegetable Gardener for the ultimate all-in-one guide to winter gardens! Growing veggies in the winter can be baffling - especially if you don't have experience gardening! This book makes it simpler.
The Best Herbs to Grow In a Greenhouse in Winter
Aside from veggies, there are plenty of herbs to grow in your greenhouse during wintertime. Some of the best plants to grow in your greenhouse during the colder months are:
Tips for Using a Greenhouse to Grow Vegetables and Herbs During the Cold Season
When gardening in your greenhouse in winter, it’s still critical to remember that it’s wintertime, and your plants will need specific care during these colder months to stay alive.
Switch to a Winter Watering Schedule
The great thing about growing vegetables in a greenhouse over winter is that you can slow down and ease watering and maintenance. Remember mid-summer when you were watering once or twice a day, and the tomatoes were turning into a jungle?!
Well, you won’t have any of that in the winter!
Winter vegetables grow much more slowly, and the lower temperatures mean they require less water. Weeds will be much easier to control, too.
This fuss-free process means that a visit to your greenhouse a couple of times a week should be plenty to keep your winter garden well-maintained. Unless, of course, you need to pop in more often to harvest vegetables for dinner!
Insulate Your Greenhouse
Although a heated greenhouse is but a distant dream for most of us, there are ways we can try to retain heat inside the greenhouse.
You can use garden fleece and cloches to create a mini-greenhouse inside your run-of-the-mill greenhouse. Water-filled containers can also act as thermal mass, gaining heat through the day and slowly releasing this through the night.
Read More – 7 Best Fermented Tomatoes Recipes! Homemade, Delicious, DIY!
Insulating and Heating Greenhouses
A greenhouse will not keep plants from freezing unless you have a heated greenhouse or very mild frosts. However, a greenhouse will keep your plants safe from cold, chilly winds and icy rain, giving them a better chance of surviving freezing weather.
To grow frost-tender plants in your greenhouse garden over winter, you may need to consider a heated greenhouse. Otherwise, consider using other frost protection measures.
How Can I Keep My Greenhouse Warm In the Winter?
You can heat your greenhouse in the winter using insulation like horticultural fleece, layers of compost, hot water, or a true heater.
Insulation, hot water, and compost may only increase the temperature by a small amount, but this can be enough to make the difference between an average or poor crop and a bountiful yield.
Tips for Insulating Greenhouses
If you want an inexpensive or free way to heat your greenhouse in the winter, you’ll want to find a way to keep the existing heat inside your greenhouse.
Most greenhouses contain a cover with a single layer of glass, Perspex, or polythene. These material covers allow them to warm up quickly in the sunshine. But, the materials will not retain heat at night.
Bubble wrap or horticultural fleece is excellent for providing an insulating layer. You can wrap the horticultural fleece around the entire greenhouse if you have enough.
The other option is to insulate just one section of your greenhouse or individual plants or beds.
A deep mulch of straw or compost will also help prevent the ground in your greenhouse from freezing. A layer of thick cardboard over the mulch gives an additional layer of ground insulation.
Water-filled containers are a simple and clever way to heat your greenhouse for free in the winter! These will absorb heat during the day and slowly release it overnight. For maximum effect, use a black container or paint it on the outside.
One final trick to heat a greenhouse is to put a compost bin inside it! The internal temperature of a well-fed composter can get up to 120 degrees Fahrenheit – imagine how snuggly and warm your plants will be with a heater like this in their greenhouse!
Greenhouse Heaters
If you’re lucky enough to have a heated greenhouse, your options for growing a diverse set of garden veggies increase. Big time! You don’t have to worry about the frost creeping in, and you can keep your delicate plants warm and happy all year round.
In winter, you can grow any of the plants suggested above in a heated greenhouse – salads, brassicas, and root vegetables. These will all thrive in a heated greenhouse and give you abundant yields right through the winter.
But maybe you wonder whether it is worth popping some tomatoes or zucchini plants into the heated greenhouse in the winter? Unfortunately, this is a strategy that is unlikely to give good results.
The first reason for this is the shortened day length. Plants respond to shortening days by going into dormancy for the winter. Dormancy isn’t a problem for your winter salads that will grow slowly even in cool weather, but your cucumbers will not like it!
The second problem is the lack of pollinating insects. So, even if you can use artificial lights to trick your summer vegetables into flowering in the winter, it is unlikely that they will set fruit successfully.
This greenhouse heater is the ultimate winter gardening hack! Keep your veggies warm during the cold weather. It heats 120 feet and comes with a thermostat!
Winter Greenhouse Growing FAQs
We know that figuring out how to get the best from your greenhouse can be a lot of work!
That’s why we’re here to answer some of the most common greenhouse winter gardening questions.
Find all the answers below!
You can grow almost anything in an unheated greenhouse in winter if it is frost tolerant. The greenhouse will protect fruits, vegetables, and plants from the worst winter weather, but they must withstand cold air temperatures.
When looking for plants to grow in a winter greenhouse, look at plants that grow north of your area. In many cases, plants like potatoes, cabbage, radishes, lettuce, and brussels sprouts are safe bets because they grow in some of the northernmost climates.
Want to increase the yield of your fresh garden veggies over the winter? Start with a winter salad bed! I’ve dedicated over half of my greenhouse to a salad bed this winter. I can’t wait for the goodies to pay off – big time.
Nestled inside my salad bed, you’ll find tender green leaves, lettuce, mustard greens, radishes, and spring onions – perfect for a seasonal salad bowl!
The other way I use my greenhouse over winter is to protect plants that will not thrive outside in cooler weather. My tender citrus trees have been brought in for the winter, as have my avocados.
As an experiment, I am also trialing a bed of this year’s eggplant, bell pepper, and chili pepper plants overwinter in the greenhouse.
Once these become dormant and the leaves fall off, I will wrap them in fleece and see what happens. I hope they will burst into life in the spring and give us an earlier harvest, but only time will tell!
A greenhouse offers superior protection for your crops than leaving them outdoors, especially during the dead of winter. Still, it may be too cold for some things you would like to flourish.
However, there are great ways to maximize the heat in a greenhouse – without investing in a purpose-built heating unit!
(I’m currently exploring the idea of Bitcoin heaters for my greenhouse. It’s insane, but Bitcoin heaters may help keep your small greenhouse warm while reducing your electric bill. We live in crazy times!)
The timing of starting seeds in an unheated greenhouse depends on your climate and last frost date. Most seeds need enough consecutive warm days and nights to germinate. Even in sunny weather, the overnight temperatures may be too cold for germination!
As a rule of thumb, you will get better germination rates in the house or a propagator until the last frost in your area has passed. After this, overnight temperatures will increase, and you can start sowing seeds into pots in an unheated greenhouse.
Final Thoughts
The moral of the story here is to stick to seasonal vegetables and use your greenhouse to extend their natural growing season by a few weeks here and there.
We also remind you that your greenhouse doesn’t have to be perfect!
Last summer, I was expecting a late overnight frost – and I just transplanted dozens of baby plants in my raised garden bed a few nights prior! Talk about bad timing. Figures. But – I didn’t panic!
I began covering the raised garden bed with a makeshift plastic wrap cover that I weighed down with stones. The greenhouse wasn’t perfect. And it didn’t look good. At all!
But it kept my baby tomato plants safe from frost overnight, and they lived to see another day.
Thanks again for reading – and please share your greenhouse questions or gardening experiences with us. We love to hear your feedback! Have a great day!
More On Winter Gardening:
Winter Greenhouses | Resources, References, and Works Cited:
- Freeze Damage To Growing Peas | University Of Delaware | Weekly Crop Update
- Growing Peas In The Home Garden | University Of Minnesota Extension Website
- Lettuce | Clemson Coop Extension | Home & Garden Info Center
- Celery | Aggie Horticulture | AgriLife Extension Website
- Growing Spinach In Home Gardens | University Of Maryland Extension Website
- Growing Spinach, The Cool-Season Vegetable | PennState Extension Website
- Radish | Texas AgriLife Extension Service
- Brussels Sprouts | Aggie Horticulture
- Planting Garlic | South Dakota State University Extension Website
- How To Grow Mustard In Your Garden | UtahStateUniversity | Yard And Garden Extension Website
