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.
- Can You Grow Plants In a Greenhouse In the Winter?
- Best Vegetables to Grow In a Greenhouse In Winter
- Insulating and Heating Greenhouses
- Winter Greenhouse Growing FAQs
- Final Thoughts
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:
- Peas! Yes, peas will grow happily in a greenhouse in the winter. They may not crop until early spring, but you will be rewarded with deliciously tender green peas long before the outdoor crop is ready.
- Winter salad leaves! My favorites are salad rocket, endives, mizuna, land cress, claytonia, and purslane.
- Leafy greens like spinach, kale, chard, and beetroot
- Brassicas, such as cabbages, broccoli, and Brussels sprouts
- Alliums, including garlic, leeks, onions, scallions, and spring onions
- Annual herbs like dill, coriander, chervil, and parsley
- Oriental greens, such as mustard leaves, pak choi, and mizuna
- Root crops, like carrots, beets, turnips, potatoes, and celeriac
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.
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!
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.
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.
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!