What Can I Grow In the Greenhouse In Winter?

Having a greenhouse really does give your garden such a boost. It not only gives you extra months of planting time each year, but it also works as a safe place for your more sensitive plants and opens up loads more choices about what you can grow. Your winter greenhouse success really depends on three things: where you're based, what size greenhouse you've got, and your personal growing aims. (Pop over to www.greenhousestores.co.uk to see our full range of greenhouses - we've got sizes to suit every garden.)

What Can You Grow in Winter

First off, you'll need to be a bit more patient in winter - plants take their time when it's cold and dark. Your veg might need double the usual growing time, depending on your local weather. Some plants might not get as big as they would in summer, but they'll still give you plenty to pick and eat. You might see weeks go by with no obvious growth - that's just fine. As long as your plants stay healthy, they'll bounce back when temperatures rise. Things tend to slow right down or pause in December and January - this is totally expected. Give them time, and you'll see fresh growth appearing as soon as the days stretch out and warm up again.

Tools For Success

Greenhouse gardening in the winter is a very different experience than at any other time of year. In a cool climate, you need to plan very specifically what you grow and when you grow it. Generally, in January and February, there isn't a lot of light or heat available so you may need need to modify your greenhouse.

Keep The Heat In

Passive Solar

To keep the greenhouse warm without using electricity, passive solar plastic bottles are a great resource. Paint plastic bottles black and fill them with water. The black paint will make them absorb the heat of the sun during the day. At night, the stored energy is released automatically and heat up the greenhouse space. Place these around your aluminum or wooden greenhouse for best results.

Electric Heaters

Fan heaters circulate air as well as heat. They also have thermostats which are a great way to be more specific with the temperature. Many also have automatic thermostats that can be set to turn on only when the temperature drops below a specific degree. A set temperature around 2C is enough to keep frost away and keep most plants well.

Heat Pads

Electric heating pads are placed under near a container to keep the plant's roots warm. This is more localized than fans or other heating methods. Depending on your set-up, it can also be cost-prohibitive if you need a lot. The main benefit is the direct heat transfer and that they can be moved around easily. Seed-starting heat mats are good, however, regular heating pads for sore muscles work well too.

Insulate

Plants can be covered with fabric row covers to reduce heat loss and create a warmer environment. This is especially important for seedlings since they are more fragile.

Straw bales placed around the greenhouse can assist with keeping heat in. It doesn't add extra heat, however, reduces heat loss which can mean a lot for the survival of your vegetables.

That's right, regular packing bubble wrap makes a great insulator. It can be layered around the inside of the greenhouse walls and frame. It can also be wrapped around individual pots to keep roots warm.

Extra Light When You Need It

When the winter gets really dark, you might want to add some grow lights to your greenhouse. It's really up to what you're growing and how gloomy your winters get - some plants need more light than others to stay happy.

Choosing Your Seeds

You'll see tonnes of different varieties for each vegetable. Go for the ones that say they're good in cold weather or quick to grow - these are your best bet for winter growing.

Keep Your Plants in One Place

Plant your seeds in their forever homes (the pots they'll stay in). Plants can get a bit stressed when you move them about,so it makes sense to let them settle in a good position with enough sun, shelter from too much wind and good soil..

Keep It Simple

With one greenhouse, it's best to grow plants that like similar conditions. Trying to create different zones in a single space is a real headache. When you keep everything at the same temperature and humidity, your plants will do much better.

Winter Stars for Your Greenhouse

Cabbage & Broccoli

These winter champions are quite particular about their temperatures - they like it between 45-55F at night and 50-70F in the day. Any warmer and they'll get grumpy. You can start them off really early, around mid to late winter, if you want to plant them outside in spring. Or just keep them growing in the greenhouse all winter - as long as you can keep those temperatures steady.

Potatoes

Plant potatoes in large buckets or thick plastic grow sacks. If they are started in January, they will be ready to harvest in March. A crop started in February can stay in any Elite or Vitavia greenhouse to maturity as well. Or, if the weather is ok, they can be moved outside and be ready to harvest at the end of April. Potatoes are susceptible to frost so if the weather is very cold, add some heat to your greenhouse or cover the plants to keep them warm.

Carrots

Plant them in the autumn and they can be harvested as soon as the ground thaws. If you're having a good winter and the ground thaws once or twice before spring, check the carrots. They may be ready. The variety of carrot makes a huge difference here so make sure you get one that is very cold-hardy.

Lettuce and Greens

Lettuce and other greens are quick growing and prefer cooler temperatures. There are some that are resistant to frost, so check your seed catalog to get the best ones. Plant these in the greenhouse in the fall and don't transplant them. They will thrive in the greenhouse as the temperatures outside drop. Harvest the leaves as soon as they are big enough; don't wait for full maturity.

For the best results, plant a wide variety of lettuce and greens. They are a large amount to choose from and they have different maturity rates and temperature requirements.

Spinach

Plant successive sowings of cool-weather loving spinach and you will be harvesting almost all winter long. There are sometimes it may slow but it will bounce back once the temperatures rise again. It grows quickly when the temperature is right which makes it an ideal greenhouse vegetable.

Kale

The cold-hardy vegetable can survive temperatures down to -6C, depending on variety. When it gets colder than that, you will need to provide some heat for it to continue or wait until the outside temperatures rise and the plants start growing again. Plant several successive crops and you can easily have kale all-year round. Bonus: Kale grown in winter is sweeter because kale produces sugar to protect its' cells.

Garlic

In January, garlic can be planted and then transplanted in March or April or whenever the soil is able to be worked. They can also be kept in their pots and moved outside when the temperature is good. Make sure to choose a hard neck variety, as opposed to a soft neck, since hard necks are the cold-hardy type.

Herbs

Coriander, dill, leaf celery, and parsley are all cold-hardy and grow well in the greenhouse during winter. Start them in late-fall and have fresh herbs throughout the winter. Their growth will likely slow during especially cold and dark days, yet it will pick up again when the temperature warms and the days grow longer again.

Vegetables To Start In The Greenhouse

Let's talk about tomatoes - they're the star of the show in aluminium greenhouses. Give them a few weeks' head start and you'll be picking your own juicy tomatoes while everyone else is still waiting. Plant your seeds about 4-6 weeks before you'd normally put them outside. Just keep the nights above 55F - they're a bit fussy about temperature. Make sure they get loads of light, either from a sunny spot or some grow lights if your greenhouse is a bit shady.

Peppers

Sweet or spicy - take your pick! All peppers love greenhouse growing. They're like tomatoes and want those warm nights above 55F. You could start them off in the greenhouse and plant them out later, or if you've got the space and can keep them cosy, they'll happily stay put all season.

Early Peas

Pop your peas in during late winter and you'll be miles ahead. When your neighbours are just thinking about sowing, you'll have sturdy plants ready for the garden. Best bit? You'll be picking fresh peas while everyone else is still waiting for their plants to flower!

Cucumbers

Get your cucumbers going in late winter or early spring. Wait until nights stay above 70F before moving them outside - they're real softies when it comes to cold.

Squash

Starting squash early in your greenhouse is a game-changer. Got short summers? This extra growing time is pure gold - most squash plants need every bit of warmth they can get to grow properly.

Okra

Okra's a bit demanding - it takes a good 2 months to grow and needs really warm soil - at least 65F. Unless you give it a nice warm start in the greenhouse, it's tricky to grow in cooler areas.

Aubergine

Get these going between mid-January and February for spring planting. Aubergines are real slow growers - in lots of places, you'd never get any without that early greenhouse start. They need all the growing time they can get!

Winter Greenhouse Gardening FAQ

What Really Works in a Winter Greenhouse

Top Plants for Winter

It's amazing what you can grow when it's cold - tough greens like kale, spinach and Swiss chard are brilliant choices. Root veg get extra tasty in winter - carrots, beets and turnips turn sweeter with the frost. And if you fancy fresh herbs, parsley, coriander and chives will keep going strong right through the cold months.

Does a Greenhouse Make a Difference in Winter?

Oh yes! Think of it as a snug bubble for your plants, blocking out bitter winds and frost. You don't even need heating - it'll naturally stay warmer than outside. Plus, you can sort out the moisture levels and light to keep your plants happy when everything else looks a bit miserable.

What Should You Not Grow?

Not everything's meant for greenhouse growing. Big trees and shrubs need more space than you can give them. Some fruit trees get confused without a proper cold spell, and plants that need really specific conditions - like those from desert or arctic places - can be fussy customers.

Keeping the Heat In

You've got plenty of choices here. Electric heaters are straightforward if you don't mind the bills, but solar ones save money long-term. A clever trick is using water barrels or big stones - they grab heat during sunny spells and gently release it at night. For smaller spaces, bubble wrap on the inside works brilliantly, and a good compost heap can pump out loads of free warmth.

Getting Your Greenhouse Winter-Ready

A good clean-up makes all the difference. Clear out dead bits that pests might fancy hiding in. Sort any dodgy spots in the glass or frame. Pop some bubble wrap up inside to trap heat. If you're growing tender plants, get your heating sorted and put them where they'll catch the most sun. Just make sure air can still move around - stuck air equals mould problems.

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