Every gardener’s dream is to have greenhouse. The appeal of a greenhouse is to have a space that you can work in – a home for a potting bench, somewhere to display your ‘show plants’ and a place to propagate. Most hanker for a place where their tender plants can safely overwinter, their seedlings can germinate, or their precious alpines can escape a battering from heavy rain. It’s a place where you can control the environment your plants are living in.
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However, it can also be a place of sanctuary – somewhere to hide from the rain, paint, read a book or even entertain friends.
Is it worth buying a greenhouse?
The possibilities are endless when you have a controlled growing space, and a greenhouse will really enhance your gardening experience throughout the year.
In spring, you can enjoy earlier harvests of tender edible crops such as tomatoes, peppers and cucumber by sowing from seed in spring, and start off hardy veg inside so you are ready to plant out as soon as the last frosts are passed. Try growing more exotic edibles such as Malabar spinach, and grow your own half-hardy annuals from seed instead of buying plants in summer.
You can continue to grow salad crops such as rocket and spinach in autumn in a greenhouse
By putting up shading you can make a home for auriculas and other alpines; growing them undercover will protect their flowers from the weather. A greenhouse is also a great place to start off softwood cuttings of perennials such as pelargoniums and fuchsias, and leaf cuttings from begonias. Mini plug plants will grow on quickly under cover too.
In summer, tomatoes, peppers, melons and cucumbers will thrive in a well-ventilated greenhouse. Start off dahlias in pots inside, protected, before planting them out in the garden, and harden off bedding plants and keep them safe from any cold nights. Succulents such as Aeonium arboreum and echeverias will thrive under glass and make great display plants.
It might be exciting to grow a grape vine to provide natural shading and fruit; and peaches are a great success under glass as the blossom is protected from frost and peach leaf curl. If the temperature and humidity are controlled, a greenhouse can be dedicated to a collection of plants such as ferns, orchids or citrus fruit. Grow scented geraniums (pelargoniums) undercover and their scent will be pleasantly overwhelming.
In autumn, enjoy large standard fuchsias, which will be protected from the wind if grown undercover. Tender salvias such as ‘Amistad’ will flower into early winter if protected by a greenhouse, and succulent plants can be moved undercover to prevent them being overwatered by the rain.
You can continue to grow salad crops such as rocket and spinach in autumn in a greenhouse, and if you move your pots of herbs under cover you can continue to harvest them all winter.
After dismantling summer container displays, you can pot on and bring pelargoniums, osteospermums and fuchias inside, and before the frosts arrive, move potted tender perennials such evergreen agapanthus undercover. Tender exotics such as banana plants, hedychiums and eucomis can also be protected overwinter if the greenhouse is kept frost free, and it would also allow you to bring on early spring blooms in pots.
Although a greenhouse will be a few degrees warmer than outside in winter it will need to be kept frost free to protect tender plants. In a heated greenhouse sweet peas can be sown any time from October until March. Also in winter, hardwood cuttings of deciduous shrubs can be kept in a greenhouse.
Do you need a greenhouse or a polytunnel?
Don’t look at greenhouse styles until you consider what you want or need one for. If you plan to grow in the ground and want as much space as possible to grow your own edibles, then a polytunnel might be a better choice.
A polytunnel can be placed directly onto the soil and can be located on sloping ground. It is not an ornate addition to a garden and is a much more affordable option, and it is easier to install yourself than a greenhouse. Polytunnels are also easy to ventilate as they often have a large door at each end, and safer in a family or community garden. However, a budget is required to recover your polytunnel every 10 years, and it’s worth knowing that on very windy sites they can be damaged by wind.
A cold frame is also the perfect companion to a greenhouse
A greenhouse, on the other hand, adds character and an elegant design feature to a garden, but can be a big investment. They require a flat, concrete slab or foundations, and often involve employing a builder to install and build footings and a wall base. They offer maximum heat retention but can easily overheat, so are more likely to require shading and additional ventilation, but are easy to ventilate if automatic vents are installed. It’s also easier to install water butts to a greenhouse.
If you are simply looking for somewhere to extend the growing season, harden off your plants, encourage semi-ripe cuttings in spring or overwinter dormant plants, then a smaller, more affordable cold frame could be all you need. A cold frame is also the perfect companion to a greenhouse, allowing you to provide plants with that half-way house between the warmth of a greenhouse and the chill of outside.
What to consider before you buy a greenhouse
There are five main points to consider before buy a greenhouse. First, decide what you need it for. Find the right location and enquire if planning restrictions apply, then set a budget and visit shows or showrooms to view options.
Location: Before you think about greenhouse style, it’s important to find the right site for your greenhouse. Locating it at the far end of the garden under a tree is not a good idea. You are looking for a site that receives the maximum amount of sunlight. The ideal is for the ridge of the roof to be following an east to west orientation, as this will extend light levels in the winter months. If you only intend to use the greenhouse in summer, then a north to south orientation is fine. Lean-to greenhouses perform best against a south-facing wall.
You are far more likely to use your greenhouse if it is located close to the house
Your chosen site needs to be level, and have the space to leave room for a path around the entire greenhouse, so you can easily clean and maintain it. Avoid placing at the bottom of a slope where flooding or frost pockets are likely to be an issue.
You are far more likely to use your greenhouse if it is located close to the house. This also makes access to water and electricity easier when installing outside taps and lighting. In the growing season, you will be nipping in and out of the greenhouse at least twice a day.
Planning and regulations: It is advisable to always contact your local council to ensure there are no planning restrictions, and use the services of a qualified electrician for electrical fixtures.
Budget: With so many beautiful and functional greenhouses on the market, it’s possible to find a design for every situation, with many companies making bespoke houses. Free-standing, hexagonal dome or lean-to greenhouses are all possibilities. If planning to go big, then you would be wise to go to a specialist company that will look after the whole process for you. They will be able to advise on planning, design, installation, ventilation, shading and heating. Many well-established companies will have ‘showrooms’, so you can step in and get a feel for a greenhouse. After a visit to such an establishment you might even decide that your new greenhouse will be a dining room or kitchen as well as a growing space.
But before you get carried away, it’s wise to establish your budget. You can spend anything from £600-£1000 for a mini greenhouse to £200,000 plus. A 6x8ft wooden greenhouse can start at about £2,500 and a 6x4ft plain aluminium greenhouse about £1,500. It’s a little like buying a car – you can choose anything from second-hand to a comfy little runaround or a supercar.
Don’t forget to set aside some budget for a base, staging, ventilation and heating.
Materials: Greenhouse frames are made of either wood or aluminium. For longevity and low maintenance, an aluminium frame is the best option. The glazing bars and frame can be thinner when made of aluminium, which allows for more light to pass through. Wood offers a very homely traditional feel and is rightly favoured by many, but a lot of upkeep and care needs to be taken to maintain it.
It's not just the choice of frame that needs to be considered. Are you opting for glass or plastic glazing panels? Glass will offer the best results, as it allows the most light to pass through (around 90 per cent), and it is not damaged over time by heat. For safety reasons, toughened glass is a sensible option.
To keep your greenhouse frost free in winter, heating is vital
The alternative is polycarbonate. This is a safer choice in a family garden where footballs may be flying – however, it doesn’t allow in as much light as glass (around 83 per cent). This option is often cheaper and safer when doing a self-build.
Design: Once you have your budget, your location, material choice and your reason for buying, the fun can begin. What design will your greenhouse be? The design is largely led by what you want to grow. The higher the greenhouse, the more light your plants will enjoy. Is it a show house or just a place for propagation? Do you need to be able to push the wheelbarrow inside? If so, make sure the door is wide enough! Do you want floor-to-ceiling glass or a brick base? Is the greenhouse a focal point, or created to reflect the age and style of the house?
Popular designs that can be bought off the shelf include: apex, a traditional design with a central front door, ideal for a small garden; lean-to, built against a garden or house wall; octagonal or hexagonal, a more ornate option that makes a real focal point.
Heated or unheated: Some gardeners choose to heat their greenhouses in winter allowing them to overwinter tender plants and start their seedlings early, whilst others choose to leave them unheated and just use them to protect plants from frost/ice and heavy rain.
To keep your greenhouse frost free in winter, heating is vital. Electric fan or tube heating is easy to control and is free from flames or liquid fuels. Gas or paraffin is a less cost-effective option but is the only option if the greenhouse doesn’t have an electric supply. It comes with a higher risk of fire or carbon monoxide poisoning. A carbon monoxide alarm is a sensible addition with this heating choice.
For larger, new greenhouses it would be worth exploring the more environmentally friendly heating options such as ground source heat pumps.
Now you've decided on a greenhouse, here is everything you need for greenhouse accessories
