Gardening, George, Greenhouses, Grow Your Own

Greenhouses are a staple of English gardens and an aspiration for all serious home-growers. But how do greenhouses work and what benefits do they provide for your plants and vegetables?

How do greenhouses work

What is a greenhouse?

A greenhouse is an external structure for growing plants, primarily made of a transparent material like glass or polycarbonate panels. They’re used in professional agriculture for growing huge volumes of crops, as well as by enthusiasts in their own back gardens. Inside you get a stable, warm environment that makes cultivating fruit and vegetables much easier throughout the year.

How do greenhouses work?

Greenhouses work by letting in as much light as possible then trapping this as thermal energy. The transparent walls and roof of the greenhouse allow all the visible rays of sunlight to pass through. This light heats up the air and objects (like the plants and soil) inside the greenhouse. But the glass also acts as an insulator, so this heat is locked inside the structure, keeping the temperatures warm all through the day.

Greenhouses are great at moderating a stable temperature. Matter within the greenhouse like soil and water absorb the thermal energy from sunlight and release it slowly, so they keep the greenhouse warm even after the sun sets. If the greenhouse contains lots of soil, the iron content within this has high enough thermal mass to regulate the temperature in this way with gradual heating and cooling throughout the day. Since the greenhouse is a closed structure, there is no breeze to disperse the warm air.

So the temperature remains constant, generally much warmer than the cold snaps we face outside, and your plants stay happy. They get all the sunlight they need to grow healthily and are sheltered from any harsh weather.

What are greenhouses used for

What are greenhouses used for?

Greenhouses effectively allow you to cheat the weather. In Britain we often have unreliable seasons at best, with cold winters and short summers. With a greenhouse you can extend the growing season – for example by sowing seeds earlier and growing vegetables like French beans and cucumbers for most of the year. Outside they would get too cold, but in the greenhouse they are protected.

The warmer environment in the greenhouse also means you can grow plants maladapted to our climate. Exotic species, such as melons and sweet potatoes, can thrive under the hot glass and delicate plants that would normally die in the winter frosts can be kept safe.

What are the benefits of having a greenhouse?

  • You can extend the growing season.
  • You can keep crops safe from pests within the physical structure, and so minimise the use of chemical pesticides you need to spray on produce.
  • You will protect plants from excessive temperatures (both cold and hot) and extreme variations in weather.
  • A greenhouse offers protection from strong winds which can damage delicate plants.
  • Shelter from rain and snow allows you to manually regulate how much water each plant is getting. This can be made easier with irrigation systems.
  • Temperatures can also be regulated with ventilation systems like auto vents to open windows and let air in, or shading to reduce light getting in during the peak of summer.
  • You can grow plants that wouldn’t normally survive in your climate.

Benefits of a greenhouse

Tips for keeping plants healthy in a greenhouse

While your plants will be kept warm and protected from the elements, you need to make sure they still get all that they need. Since they won’t receive water naturally from rain, you must remember to water regularly or set up an irrigation system to do this for you. It’s also worth setting up greenhouse guttering and a waterbutt to harvest rain falling on the roof.

During the summer months, the greenhouse can sometimes get too hot, which isn’t healthy for everything growing. So be sure to open a window or door if it gets too stuffy. You can also use a ventilation system like louvre windows or automatic vent arms to manage this for you. If excessive sunlight is causing the greenhouse to heat up uncontrollably, then hanging or spraying temporary shading on the roof windows can alleviate this.

Your greenhouse will also need taking care of to make sure it’s at its best year after year. This includes things like an annual deep clean, sterilising pots and checking for damage. You can read more in our greenhouse maintenance guide. Also make sure that you keep on top of pest control in your greenhouse.

Lacewing greenhouse

Different types of greenhouse

Thankfully there’s not just one type of greenhouse to satisfy all gardeners. If you have space, then it’s worth getting the biggest freestanding one you can to maximise your growing area. But if space is limited then you can get a lean-to greenhouse attached to the side of your house, which offers the same robust frame and panels. For allotments and patio gardening, mini greenhouses and cold frames provide very compact space for crops, and can be portable too.

Read more about how to choose your greenhouse.

So we hope you now have a better understanding of how greenhouses work and why they’re such an invaluable treat for hobby gardeners and pros alike. If you’re interested in buying one for yourself, Primrose has a great range of high quality greenhouses available.

George at PrimroseGeorge works in the Primrose marketing team. As a lover of all things filmic, he also gets involved with our TV ads and web videos.

George’s idea of the perfect time in the garden is a long afternoon sitting in the shade with a good book. A cool breeze, peace and quiet… But of course, he’s usually disturbed by his energetic wire fox terrier, Poppy!

He writes about his misadventures in repotting plants and new discoveries about cat repellers.

See all of George’s posts.

George, Greenhouses, How To, Pest Advice, Pest Control, Slugs & Snails, Spiders

Greenhouse Pest Control

Greenhouses are wonderful tools for keen gardeners, offering a much needed space to tend to gardening projects outside of the usual summer season. But while protecting your plants from the elements, greenhouses can also be prone to sheltering pests and diseases that will ruin all your hard work. Armed with our top greenhouse pest control tips, you should be well equipped to give your plants the best protection possible.

1. Keep your greenhouse clean

As with any form of disease or pest prevention, cleanliness is the number one priority. As part of your general upkeep, it’s worth thoroughly emptying and cleaning out your greenhouse once a year. This involves washing down the windows and surfaces, hosing off the floors and cleansing all the pots. Doing this should give you a fresh, pest-free start for growing each year.

2. Inspect your plants

It’s vital to check over all your plants before they enter the greenhouse in order to prevent pests spreading inside. Just as flowers and crops love the warmth of a greenhouse so too do bugs, and they multiply in the heat. So give any new plants a thorough inspection for signs of insects or larvae on the leaves or stem before bringing them inside.

3. Disinfect your tools

Most gardeners will regularly use the same tools all round the garden, transporting them around the shed, flowerbeds, lawn, vegetable patch, compost heap and greenhouse. This means they can pick up pests from the soil outside and infest the plants inside the greenhouse. So to be extra careful, it’s worth giving your spades, trowels and other tools a good clean every now and again – a soak in soapy water should do fine.

4. Use insect catchers

Chances are, insects will always find a way into your greenhouse. Catch them where they fly, with simple greenhouse pest control products, like hanging fly papers and wasp traps, or using spider spray at the door.

5. Use netting

Obviously, greenhouses need good ventilation and it’s never worth sealing them up completely to stop incoming pests. But you can easily cut down on the number of large flying insects entering by hanging netting across open windows or other vent points.

6. Move pots outside in the heat

In the summer months, greenhouses can often become hot and dry throughout the daytime. Moving potted plants outdoors not only helps cool them down but also reduces the build up of spider mites on the plants. Spider mites increase rapidly in number in dry heat so it’s worth keeping the greenhouse ventilated and also using a mister to keep the humidity up. If you’re going out for the day a good trick is to dowse the floor with water, which will evaporate into the air throughout the rest of the day.

7. Use potting soil

Often regular soil from the garden will be packed full of creepy crawlies, insect eggs and other pests. So for the container plants in the greenhouse, it’s a good idea to pot them in shop-bought potting soil or compost. This should be sterilised free from any pests or diseases and well as being rich in nutrients to help the plants grow.

8. Rotate crops

If you plant directly into the ground inside your greenhouse, clearly you won’t have as much control over the spread of potential pests within that soil. A method of combatting this is crop rotation – each year vary what type of plant you are growing in that piece of ground. This tends to prevent the buildup of pests in the soil, as similar plants usually encourage the same types of pest.

9. Freeze the pests

This is an extreme measure that you could perform once a year if you believe your greenhouse is truly infested. During the winter, allow your greenhouse to enter a chilling period by opening up all the doors and windows for a day or two. The temperature will drop right down, killing off any pests inside, including their eggs and larvae. As long as it’s not cold for too long, the plants should survive this. Obviously, any tropical plants or those that require constant warmth should not be left out for this.

10. Use biological pest control

Many common greenhouse pests, such as vine weevil grubs, whitefly and spider mites can be fought with biological control. Each pest has a corresponding organism that you can introduce to the infested area and it will feed on the pest, keeping its population under control. If the pest is eliminated then the control dies out too due to lack of food source, so you don’t need to worry about them destroying the plants instead. Some of these biological controls are available to purchase.

Hopefully by putting these tips into practice, your greenhouse will remain pest-free and your plants will thrive. Let us know how you get on or if you have any greenhouse pest control advice of your own!

George at PrimroseGeorge works in the Primrose marketing team. As a lover of all things filmic, he also gets involved with our TV ads and web videos.

George’s idea of the perfect time in the garden is a long afternoon sitting in the shade with a good book. A cool breeze, peace and quiet… But of course, he’s usually disturbed by his energetic wire fox terrier, Poppy!

He writes about his misadventures in repotting plants and new discoveries about cat repellers.

See all of George’s posts.

Gardening, Gardening Year, Greenhouses, Grow Your Own, How To, Kim Stoddart, Planting

I keep hearing what a harsh winter we’re going to have this year. It’s even been dubbed Freezageddon by some commentators, which is a little dramatic if you ask me. None-the-less, whether it is going to be the coldest winter in 50 years, or indeed just ….cold, having a greenhouse or polytunnel in which to grow over winter is very handy indeed.

For a start, even when there’s thick snow on the ground all around, you’ll still be able to dig out (and pick) some of your vegetables from inside. For a badly behaved gardener like me who loves gardening and doesn’t like having to wait till spring to get active again, I couldn’t imagine doing without.

Cleaning the Polytunnel
Be sure to keep your polytunnel clean over winter

Growing inside enables you to naughtily extend the growing season, carrying on that bit longer and starting earlier in the year. It boosts results from harder-to-grow, warmer climate craving produce no matter where you live and what the seasons throw at us.

Plus on a rainy day (and let’s face it we’ve had a fair few of those recently) you can still happily garden away protected from the elements.

Even the smallest, unheated polytunnel or greenhouse can make all the difference. While extra tricks such as using ground cover to warm the soil, using a cold frame for extra protection and an inside heating system will expand your opportunities even further…

Here are just a few of best things about growing inside:

Earlier planting

Peppers, aubergines and chillies in particular need a longer growing season and the professional growers I know all start them in January/February for a bumper crop.

Tomatoes and cucumbers also benefit from being inside, even the hardier varieties and especially here in West Wales.

Everything in fact can be germinated and planted out just that bit earlier…

Growing more exotic varieties

There is much more room for experimentation and growing a wide range of exotic and rather exciting plants that you might otherwise not have tried. Melons, sweet potatoes and okra are worth trying and more sensitive, heat-loving fruit trees such as cherry, lemon and lime and peach really benefit from being kept inside in pots over winter. Although the citruses will need extra protection if the thermostat does indeed plummet as predicted.

Later planting

If you’ve been a bit slack with some of your planting and maybe missed your usual planting dates, it doesn’t matter when you grow inside because seedlings will have that bit extra time to catch up. As long as it’s not too late and the plant has established itself (before the shortest days) it will remain intact (and fresh) for a lot longer than during the summer months. Some of the best for lazier, later planting include spinach, rainbow chard, winter salad leaves and cress which all shoot up quickly given half the chance.

So don’t fear the weather doom-mongers. Yes, they could be right but come rain, hail, snow… whatever climatic conditions are thrown at us; with just a little outside protection you can ensure that you and your produce are warm enough inside, which is where it counts.

Kim StoddartKim Stoddart is a gardening writer for the Guardian and blogs at www.getbadlybehaved.com.

Animals, Bird Baths, Garden Design, Garden Tools, Gardening, Gardening Year, George, Greenhouses, Heated Clothing, How To, Planting, Plants

Gardening in Winter

When the cold winds blow and snow begins to settle on the lawn, it’s tempting to close the backdoor and spend the winter curled up by the fire. But if you’re an outdoorsy person then there’s no need to give up on the garden for a whole season every year. With our guide to gardening in winter you’ll find plenty of projects to crack on with before the spring, how to protect your plants against the cold and top tips for making the most out of your time outdoors.

Winter Gardening Jobs

  • Pruning. Some plants are best cut back and pruned over winter, such as roses, shrubs, fruit trees and deciduous hedges. This will encourage healthy new shoots to grow when the weather warms up again.
  • Cleaning. While the life in your garden is less demanding, it’s a good opportunity to sort out a bit of general maintenance. Hosing down your paths and patios will not only spruce them up, but also ensure they’re free of grime which could become slippery in the cold, damp conditions.
  • Checking for structural damage. If you have a greenhouse, conservatory or shed then winter is the best time of year to give them a good inspection. Most of the surrounding foliage will have died back, leaving a clear path to see any cracks in the frames or broken window panes. Fixing these now is crucial for protecting any plants inside from freezing draughts.
  • Ordering seed catalogues. Get prepared for the sowing season by choosing seeds and plants to buy. It’s a good time to sit back and plan how you might like to redesign your planting or reflect on which flowers grow best in your garden.
  • Cutting the lawn. You won’t need to mow the grass anywhere near as frequently as in the summer, but if the weather is mild it will need doing every now and then. The grass won’t grow as fast, so you can leave it longer than normal.

Winter Gardening Tips

  • Don’t compact the soil. During wintertime, the ground will likely be saturated from excess rain and freeze due to the plummeting temperatures. It’s best to avoid treading on the earth too much as you will compact the already dense soil, making it even more difficult to work in the spring. So try to step lightly when you need to go over it.
  • Maintain tools. There won’t be many labour intensive jobs to do in the garden over winter so it’s a good opportunity to show your tools some TLC. Oil any machinery that requires it and sharpen the blades of your trimmers and secateurs. Then you’ll be all set for cracking on when the frost thaws.
  • Keep watering. It’s easy to overlook watering your garden when the weather’s so rubbish this time of year. But it’s still important to go outside and give your plants a quick water every now and then, particularly if it hasn’t rained in a while. And don’t forget to water your indoor flowers too!
  • Plan ahead. Winter is a great time to plan your garden design for the coming year. Most of the plants and trees have died back, leaving the core layout of your plot clear. Take advantage of this by mapping out new paths or patios, or deciding where to put that new shed or greenhouse.

Trees in Winter

Winter Planting

  • Winter loving plants. Surprisingly, there are a few plants that defy nature and come into their own in the chilly months. Besides evergreen trees, these include witch hazel, winter jasmine, winter honeysuckle and viburnum. Add a few of these for a colourful flowerbed all year round.
  • Winter vegetables. If you have an allotment or kitchen garden, then there are plenty of hardy vegetables that will keep you going over winter. In early summer you can sow broccoli, leeks, winter cabbage and brussel sprouts, which are all capable of enduring the frost – and perfect for a Christmas dinner!
  • Frost protection. As any gardener will no doubt be aware, most plants don’t take well to frosty nights and freezing temperatures. There are many methods to protect your plants against frost, from cloches and fleece blankets to careful watering and layering mulch.
  • Indoor gardening. Perhaps the simplest way to get your gardening fix without having the brace yourself against the chill is by planting inside. Not all plants will grow well indoors, so make sure you do your research. Most plants will grow best in rooms full of light and insulated against draughts. For the most effective indoor growing, it may be worth investing in specialist lights and a grow room.

Winter Wildlife in the Garden

Wintertime can be harsh for animals in the wild. Food is scarce, conditions are icy cold and shelter is hard to come by. You can help out the creatures that come to your garden by providing a little assistance. For the birds, leave out extra food in your birdfeeder and keep your birdbath topped up with water – though make sure it doesn’t freeze. A tennis ball in there should do the trick. You can also plant berry bushes, which will provide a source of winter food and a place to shelter.
For other creatures, make sure there’s somewhere for them to bunker down and sit out the winter months. Simply leave out a pile of leaves or uncut grass for groundlings to nest in.

Bird in Winter

What to Wear Outside

Obviously the priority when gardening outside from November to February is keeping warm. Wrap up as much as you can with hats, gloves, scarves and coats, while allowing enough ease of movement to be able to get on with your digging and pruning. A great way to cut back on the layers while retaining the warmth is with heated clothing. You can use heat pads for your hands or even battery heated socks and gloves for long-lasting toastiness. Just make sure that you don’t spend too long outside at a time, especially if you’re feeling unwell. There’s nothing like a regular tea break to warm yourself up!

One Year Ends, Another Begins

So don’t let the cold weather and long nights dishearten you too much – there’s still plenty of opportunity to get outside and enjoy your garden in winter. From protecting the plants you’ve tended all year to planning new features for the next, winter is the perfect time for reflection and inspiration. Take a brisk walk through the grass before huddling up inside with a hot drink and admiring your garden through the window. Treat someone special to a book full of gardening ideas for Christmas. And most of all get ready, for spring will soon begin!

George at PrimroseGeorge works in the Primrose marketing team. As a lover of all things filmic, he also gets involved with our TV ads and web videos.

George’s idea of the perfect time in the garden is a long afternoon sitting in the shade with a good book. A cool breeze, peace and quiet… But of course, he’s usually disturbed by his energetic wire fox terrier, Poppy!

He writes about his misadventures in repotting plants and new discoveries about cat repellers.

See all of George’s posts.

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