Most of us think of the greenhouse as a summer gardening accessory, there to help our tomatoes, peppers, and cucumbers flourish and produce an abundant crop.
It is common to see greenhouses left sad and empty through the winter, but could you be using this valuable growing space for anything else during the cold weather?
Yes, you definitely can!
It is easier if you imagine your greenhouse as a multifunctional and versatile year-round growing space:
- A greenhouse will maintain warmer temperatures in the summer, so 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.
- And in the winter, a greenhouse gives you a perfect little microclimate to keep plants sheltered from the worst of the winter weather!
Think about it – when the worst of the winter weather hits, your greenhouse will provide shelter and protection for your plants!
- Winter Gardening Using Greenhouses
- Best Vegetables to Grow in a Greenhouse in Winter
- Winter Greenhouse Growing FAQs
- Do Greenhouses Keep Plants Warm in Winter?
- What Can I Grow in an Unheated Greenhouse in Winter?
- Can You Grow Vegetables in a Greenhouse in the Winter?
- What Vegetables Grow Well in a Greenhouse in Winter?
- How Cold is Too Cold for a Greenhouse?
- When Can I Start Seeds in an Unheated Greenhouse?
- Will a Greenhouse Keep Plants from Freezing?
- How Can I Heat My Greenhouse for Free in the Winter?
- What Can I Grow in a Heated Greenhouse in Winter?
- Our Final Greenhouse Tip for Abundant Winter Veggies!
Winter Gardening Using Greenhouses
Whether you have rain, hail, snow, or icy winds, your greenhouses will stay dry and draught-free.
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 a worthwhile investment, we’d say it is! And using it all year round means it will pay for itself even quicker.
However, one important thing to remember is that your greenhouse will not massively improve the overall growing temperature for your crops in winter.
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.
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!
I know this from experience, as our first frosts here have just finished off 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 some 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 taking the time to plan what you want to grow.
Let’s also look at 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
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.
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.
- Spring onions
- Annual herbs – dill, coriander, chervil, and parsley
- Oriental greens – mustard leaves, pak choi, and mizuna
- Leafy greens, either picked small for salads or use the larger leaves for cooking – spinach, kale, chard, beetroot leaves.
The second group is winter greenhouse vegetables that grow happily outside in the coldest weather.
However – growing them in the greenhouse will speed up the growth and potentially give you bigger yields. They will also have protection from pests and harsh weather in the greenhouse.
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Any of the following winter veg crops will thrive in a greenhouse:
- Brassicas – cabbages, broccoli, and Brussels sprouts
- Root crops – carrots, beets, turnips, celeriac
- Alliums – leeks and scallions
So, it is worth planting some of these both outside and in the greenhouse. Diversifying your crop in this way should give you a constant supply, and if one crop fails, you’ve got the other as a backup!
Tips for Using a Greenhouse to Grow Vegetables in Winter
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!
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.
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 happily answering some of the most common greenhouse winter gardening questions.
Find all the answers below!
Do Greenhouses Keep Plants Warm in Winter?
Greenhouses are great for protecting plants from the worst of the winter weather. They will keep snow, hail, icy rain, and chilly winds at bay, giving you an advantageous little microclimate.
However, a greenhouse will still have a low air temperature. On a sunny day, it could get quite warm! But, overnight, the temperature will plummet.
So, unless you have additional heating and frost protection measures in place, your tender plants will still feel the cold in a greenhouse in the winter!
What Can I Grow in an Unheated Greenhouse in Winter?
You can grow pretty much anything in an unheated greenhouse in winter, as long as it is frost tolerant. The greenhouse will protect fruits, vegetables, and plants from the worst winter weather, but they must withstand cold air temperatures.
Can You Grow Vegetables in a Greenhouse in the Winter?
Yes, the 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.
What Vegetables Grow Well in a Greenhouse in Winter?
Want to increase the yield of your fresh garden veggies over the winter? Start with a winter salad bed! This winter, I’ve dedicated over half of my greenhouse to a salad bed. I can’t wait for the goodies to pay off – big time.
Nestled inside my salad bed, you’ll find tender green leaves, lettuces, mustard greens, radishes, and spring onions – perfect for a seasonal salad bowl!
The other way that 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!
How Cold is Too Cold for a Greenhouse?
A greenhouse offers superior protection for your crops than leaving them outdoors – especially during the dead of winter. But, it may well still be too cold for some of the things you would like to flourish.
However, there are some 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 an insane topic – but Bitcoin heaters may help to keep your small greenhouse warm while also reducing your electric bill. We live in crazy times!)
When Can I Start Seeds in an Unheated Greenhouse?
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.
Will a Greenhouse Keep Plants from Freezing?
Unless you have a heated greenhouse or very mild frosts, a greenhouse will not keep plants from freezing. However, a greenhouse will keep your plants safe from cold, chilly winds and icy rain, giving them a better chance of surviving freezing weather.
If you want to grow frost-tender plants in the greenhouse over winter, you may need to consider a heated greenhouse. Or, consider using other frost protection measures.
How Can I Heat My Greenhouse for Free in the Winter?
There are some great hacks you can use to keep your greenhouse warmer in the winter! These 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.
The first thing to consider is how 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. If you have enough? You can wrap the horticultural fleece around the entire greenhouse. 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!
What Can I Grow in a Heated Greenhouse in Winter?
If you’re lucky enough to have a heated greenhouse, your options for growing a diverse set of garden veggies increases. 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.
You can grow any of the plants suggested above in a heated greenhouse in winter – 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 about 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.
Read More – How Long Does It Take to Grow a Christmas Tree?
Our Final Greenhouse Tip for Abundant Winter Veggies!
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 the frost overnight.
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!