When you’re preparing your greenhouse for winter, the most important factor is whether or not you will heat your greenhouse. If you heat your greenhouse, you can use it to move some of your outside summer plants too, so they can survive the cold winters. If you don’t heat your greenhouse, check which plants can grow in colder climates. Protect your plants with our tips!
Most of these tips are focused on an unheated greenhouse, although many of them can also be used with a heated greenhouse. We have foreseen some extra info on heated greenhouses below!
Winterizing your greenhouse with these steps
Step 1: Clean your greenhouse
Although I’m not particularly a fan of cleaning, this is one of those jobs that just needs to be done. Especially when the outside of your greenhouse is getting a little green, it’s important to get the windows clean. During winter, the light needs to be able to reach your plants and the sun needs to heat up your veggies whenever it gets a chance.
For the outside, it’s best to use a product that will also clean off the moss and fungi on your glass or polycarbonate panels. Make sure you get a different product for the inside, as this will be too aggressive to clean with so close to your plants. Try to find a biologically degradable product with no chemicals in it, so it doesn’t harm your veggies and plants.
Step 2: Prepare the soil
Start by removing all dead plants and plants that might have picked up a disease during spring or summer. Placing some worms in the soil of the greenhouse will help you to make the ground airier and healthier to start planting again in spring.
Step 3: Plant your winter greens
Does your climate allow winter growing? Not only Californa greenhouses can still produce vegetables during winter! Some veggies are well equipped to survive winters in a greenhouse. By the end of autumn, you need to start planting your winter greens, such as spinach, leek and carrots. Make sure you plant before frost hits because you won’t be able to dig into the ground when the soil is frozen.
Step 4: Insulate your greenhouse
To protect your greenhouse from frost, it’s advised to insulate your greenhouse. We have a whole article on insulating your greenhouse during winter (and summer for that matter). Take a look and increase your chances on healthy vegetables during winter.
Step 5: Plant covers
When you are winterizing your greenhouse, you can also get extra plant covers. Each layer will make them better protected against frost and increase their chances of surviving winter.
Step 6: Ventilate
While it may seem a little weird, even during winter you need to open windows and doors every once in a while. You don’t want the air inside your greenhouse to become too humid, this will have a negative effect on your plants. Open your windows during sunny periods and when temperature is below freezing to literally clear the air.
Step 7: Harvesting time
When you’re harvesting your winter plants, do it on the warmest time of the day. When you harvest frozen plants, they will break and you won’t be able to eat them. Wait until the sun is at its highest and harvest your crops.
Step 8: Don’t water your plants (too often)
Sounds weird right? Trying to help your plants survive by not watering them? During winter, most plants are in ‘sleep mode’. Sleeping plants don’t need much water, especially not when it’s very cold. In winter you don’t need to water your plants more often than every 2 or 3 weeks, and it’s best to do so on a warmer day.
Bonus tip: Location matters
Are you setting up your first greenhouse? Figure out the best spot in your backyard to catch as much sun as possible during winter, but allow your greenhouse to benefit from some shade in summer. Especially when you want to grow in winter, you need every ray of sun you can get!
Heated greenhouse during winter
A heated greenhouse during winter will give you the opportunity to grow a wider range of vegetables and plants and to start growing spring vegetables earlier than in an unheated greenhouse.
When you have a heated greenhouse, you can use it to have your plants survive winter, so you don’t have to start from scratch during spring. You won’t make it as warm as a greenhouse would be in summer, the focus is on keeping frost out, so your veggies and plants don’t freeze and you can enjoy fresh homegrown vegetables all winter long. In our article on greenhouse heating you find all info about how to heat your greenhouse.
Your most asked questions answered
Here’s an overview of winter related questions we often get.
Can greenhouses be used in winter?
People often ask us if a greenhouse will work in the winter? Off course it will! It’s up to you to decide what you want to use your greenhouse for. If you want to use it as a place for your summer and spring plants to survive winter, you will probably be ok by just insulating your greenhouse and keeping the frost out (unless you live in an extremely cold climate).
If you however want to use your greenhouse to grow winter vegetables, you need to check which temperatures are necessary for your plants. You can do this by heating and insulating your greenhouse and by making sure you prepare your greenhouse thoroughly for the winter to come. Once again, the climate you live in is an important factor in this one, so think about what kind of temperatures your greenhouse will need to undergo when you decide how you will use and protect your greenhouse.
Will a greenhouse keep plants from freezing?
There’s no simple answer to this one, as it depends on the climate you live in. Is your winter harsh and long? Then you will probably need to foresee some extra measures to keep your plants from freezing. Is your climate more moderate and does it only freeze during a short amount of time and not very hard? Then you can probably get along by insulating your greenhouse and making sure it gets plenty of sunshine to heat up during the day.
The best way to make sure your plants are not freezing, is by installing a thermometer in the greenhouse and keeping a close eye on it. When the temperature drops below freezing point, you can insulate your greenhouse or add greenhouse heaters.
Do greenhouses need to be heated?
Does a greenhouse need a heater to make sure you can keep growing in winter? There’s no simple answer to this one as it largely depends on the climate you’re in. If you’re in an area with lots of frost and snow and you want to keep growing vegetables or plants you will need a heating system to keep the frost outside.
Make sure your greenhouse gets lots of sunlight, as this will heat up your greenhouse (also during winter) and will make the extra heating less necessary on sunny days. When you’re in a more moderate climate and there’s no or hardly any frost or snow, you can probably go without heating. In any case, whether you will use a heater or not, it’s always a good idea to insulate your greenhouse. When you heat it, the heat will be kept in the greenhouse more efficiently and without heating you can win a couple of degrees. The best thing to do is install a good thermometer in your greenhouse and check when you think it might be getting too cold. There are definitely some good value for money hobby greenhouse heaters on the market.
Will a greenhouse stay warm in winter?
This one also depends on the climate you’re in. Can greenhouses grow plants during winter? Yes, they can but there’s a few things you need to pay attention to. The temperature in a greenhouse will in general be a couple of degrees warmer than outside, because when the sun shines on the glass op plastic, the heat will be held in the greenhouse.
However, during frost, there’s no guarantee that the temperature in your greenhouse will stay above freezing point. Luckily there are some steps you can take to avoid your crop from freezing. The most important one is to prepare your greenhouse for winter. If you live in a cold climate, it would also be a good idea for you to explore greenhouse heating options. This way you will be able to enjoy your greenhouse all year long!
We hope this greenhouse winter advice will help you prepare. Do you have another great winter greenhouse tip?
Let us know!