The greenhouse effect

A fully productive greenhouse is similar to having a family pet – it will need a bit of your attention every day! Despite the hard work, once you’ve reaped the rewards of tasting your own chili peppers, peaches or tomatoes and raised your own garden plants for a fraction of the price charged at the garden centre, you’ll be hooked and wonder how you ever managed before your greenhouse came along.

Owning a greenhouse is good for your health, as it allows you to escape from all the stresses you have and nurturing plants indoors will definitely lift your spirits even on dull days

Buying a greenhouse can be quite bewildering though, as there is a vast choice but fortunately ones to suit every taste and budget. It makes sense then to draw up a list of your requirements and consider which shape will best fit in your garden design – they’re not all shaped like a glass box with a span roof.

Greenhouses are traditionally made from timber, which has the advantage of being able to be fashioned to any style and custom-built to your spec. It is also a good choice for coastal areas, where aluminum tends to corrode, leaving the shiny metal with a flaky, grey matt coating, however, in the main, aluminum structures are maintenance-free. 

If your budget will stretch, you might prefer to go for powder coated aluminum in a colour. Green is the most popular, though it’s possible to find greenhouses painted black, white, brown, grey and even burgundy. You also have the choice of free standing or space-saving lean-to structures.

As a greenhouse is considered to be a big investment, it makes sense to shop around and check what design features are fitted as standard by the different manufacturers. 

The cheapest greenhouse is not always the best buy as often the glass is not included in the kit. Many firms, however, include not only the glass but a prefabricated base and even staging as part of the package, so what seems to be an expensive model, can very often work out to be cheaper.

To maintain a healthy atmosphere for plants to thrive, it’s important to have adequate ventilation and pay attention to cleanliness, as dirt and grime harbours
disease and leaves an open road for pests to invade

The first thing to check for is an adequate number of ventilators. You cannot have too many, especially if you want to grow alpines. In this case you can go for a model where the bottom is clad with wood or brick as these tiny plants will need to be plunged into sand on a sturdy staging.

If you intend to grow alpines you’ll need to invest in sturdy staging

Few standard greenhouses have a door sufficiently wide enough to take a wheelchair and it needs to be at least 36cm if you’re going to be able to carry a large tray of plants through without scraping your knuckles.

The type of door used is an important consideration too. There are models with hinged or sliding doors and although on a windy site the sliding type is an advantage as it will not swing open or slam shut. In my experience sliding doors on some of the cheaper models, do tend to come off their runners if you pull them too vigorously or get jammed when dirt inevitable gets stuck in the track. Sliding doors however, are best in small gardens where space is tight. 

If you’re unable to have a water supply laid on to the greenhouse, guttering will be an advantage to trap rainwater but take note that if you opt for a curved-eave design or dome-shaped greenhouse there are no eaves on which guttering can be fixed.

The risk of broken glass is eliminated by the use of PVC to construct the glazing panels, making it safer for allotments and where pets and children to play in the garden

You should always choose the largest greenhouse you can afford or accommodate. In a very small greenhouse it is difficult to maintain optimum conditions as the slightest change in the weather causes temperatures to soar or fall immediately. Ideally go for extra width than length as you will need to same size path in whichever size you buy and in a narrow house this means using valuable border or bench space. 

A greenhouse with glass right to the ground allows in more light, which you’ll find useful if you plan to grow tomatoes, cucumbers and flowers for cutting. For these crops the height of the greenhouse, especially to the eaves, is critical if they are to attain their full growing height without being impeded.

If you only intend to use the greenhouse for propagation and pot plants and have no use for the area under the staging, other than for storing pots and trays, it would be sensible to choose a half-clad design or use polystyrene sheets to cover over the glass. This would save you money on heating bills as less heat will escape through brick or wood cladding and this will give you year-round adaptability. 

As well as glass, you will find that cheap polythene clad models are available. These are ideal for growing salad crops in summer and for extending the season by a few weeks. But they are not much good for overwintering frost-sensitive plants like fuchsias and bedding geraniums. To do this you’ll need to invest in a heater and line the inside of glass greenhouse with bubble wrap polythene to help prevent heat from escaping and of course have some staging to keep the plants off the ground.

Designs that have sloping sides and extra large panes of glass offer less headroom but better light transmission, which might be useful if you want to grow winter crops and the mansard or curvilinear shape, which is popular with serious greenhouse gardeners, is best if you intend to raise plants from seeds and cuttings in spring as the shape of the greenhouse has glass panes set at various angles, which trap as much light and solar heat as possible. 

Another deciding factor maybe that cheaper aluminum houses are glazed using spring-loaded clips whilst more sophisticated glazing systems that have glass held in place with a continuous capping mean that glass fits snugly, reducing draughts and drips.

Who sells what

Affordable is the Parlam Harmony Silver Greenhouse, which is available from Argos

Argos (agros.co.uk) offers the Palram Harmony Silver Greenhouse (1.8 x 1.2m) for the budget price of £281.99. It has an aluminium frame and clear polycarbonate glazing. It also features integral rain gutters and an integral base and lockable door, which is included in the price.

greenhousestores.co.uk is an easy to use website, offer the best prices and discounts with a simple ordering process and after sales service. 

Elite Greenhouses (available from www.greenhousestores.co.uk) have a comprehensive range to suit all needs, whether you want a tiny patio lean-to all the way up to a 3.6m wide semi-commercial glasshouse. Prices start at £279 for a lean-to model and £399 for a 1.85 model with opening roof vent. You will get free home delivery in the price.

Alitex National Trust Scotney greenhouse is state of the ark. The brick base and cold frame are extras and made to your requirements

Alitex is well known for its bespoke Victorian style greenhouses, which are endorsed by Kew and the National Trust offer some of the most stylish designs plus a bespoke service that can create more or less anything you desire. Alitex.co.uk use the highest quality aluminium. They offer 8 ‘free standing’ designs in 6 heritage inspired colours. Sizes from 2.4m x 3m to 2.9 x 7.1m with a starting price of £11,250.

Hartley Patio Glasshouse is perfect for small gardens

You can buy heritages-style greenhouses as well as modern greenhouses from Hartley-botanic.co.uk. To celebrate Hartley Botanic’s 80th anniversary, the company has launched the new ‘Ruby Red’ Patio Glasshouse this year. From micro gardens, to patios and balconies to roof gardens, Hartley Botanic’s Patio Greenhouse provides the ultimate compact growing area for urban gardeners as well as an additional space for larger gardens. The Patio Glasshouse offers gardeners the same enduring strength, longevity and performance of its larger counterparts and comes with a 10-year guarantee. It’s available in a variety of colours and costs £1200.

The location of your greenhouse is very important if you are to get the best out of it. A well-drained, sheltered and sunny spot is ideal. Badly drained ground will cause many problems, especially in winter when the cold, damp air, will encourage fungal diseases. Good ventilation is also crucial for plant health, as a stagnant atmosphere will weaken and stress plants making them vulnerable to pest and disease attack.

If your main reason for getting a greenhouse is to grow your own bedding and hanging basket plants so that you can try out varieties both new and old, which are only available as seed or plug plants, think again! there is much more you can grow.

If you are worried about heating costs – don’t. Even in an unheated greenhouse you can still have a colourful display in the drabbest months if you force hardy winter and spring flowering shrubs and herbaceous perennials. Select some of the more choice shrubs such as camellias and showy perennials like the Christmas rose or Helleborus niger.

Hardy annuals and biennials often make wonderful pot plants too. For the brightest displays from mid winter until spring, sow calendula, polyanthus and auriculas in late summer and sow ten-week stocks in autumn to provide plenty of good quality blooms for cutting in late spring. When sowing stocks for cutting, discard the dark green seedlings, as these will only produce plants with single flowers and prick out the paler coloured ones, which produce double blooms.

Take the temperature to just above freezing and you can grow some magnificent winter pot plant displays with cyclamen, Primula obconica and Primula malacoides. Simply start the seeds off in a heated propagator or on a windowsill indoors and raise them in a cool frost-free temperature.

These and other flowering pot plants would make beautiful gifts at Christmastime. In a temperature maintained just above freezing, you can also plant the corms of Anemone ‘St Brigid’ and ‘De Caen’ in pots as these will give a reliable show of flowers for cutting at a time when those that are planted outdoors are looking a little weather-beaten. 

Other delicate annuals that can be relied on the give spectacular displays with the protection of a cold greenhouse are Salpiglossis sinuata and schizanthus, which is also known as the butterfly flower. Plants of Cineraria maritime, with silvery leaves used for summer bedding, also makes a good winter display depending on how chilly the greenhouse gets, and make an impressive colour combination with purple-leaved Spiderwort or setcreasea.

If growing edibles in your thing, then in summer, use your unheated greenhouse for growing tomatoes, aubergines and chilies or cucumbers and melons, which thrive in slightly warmer and humid conditions – damping down the floor on hot days will add moisture to the air. Be mindful that these tender plants need to be sown early in the warmth so if you can’t afford to heat the greenhouse at this crucial time buy young plants along with tender vegetable plants like Runner and French beans and sweet corn to be grown on outdoors when the risk of frost is passed. 

Summer salads that can be sown and grown to maturity in a cold greenhouse include beetroot, lettuce and radish. Keep temperatures above freezing and you can also experiment and grow your own lemon grass, root ginger and citrus to use in your favourite Asian recipes.

in winter and without heat you can force pots of new potatoes for Christmas, spring bulbs to flower in late winter and also grow hardy oriental greens. To give your family a treat grow grapes and figs if you have the space. Your greenhouse will also allow you to eat fresh strawberries in May and again in November extending outside crops, which naturally fruit from late June to early August.

There are plenty of time saving and useful gadgets to help such as automatic ventilators and irrigation systems as well as tricks to help prevent temperatures from soaring such as painting the outside of the glass with Vitax Summer Cloud Greenhouse Shading paint, which stays on in wind or rain and can be wiped off with a duster.

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