A greenhouse is a must for the keen gardener – it’s ideal for sowing seeds, taking cuttings, growing tender plants and crops and overwintering tender plants.
There are a huge array of options when it comes to choosing a greenhouse, and prices can vary from a few hundred to many thousands of pounds. The greenhouse you eventually choose will come down to two main factors – the area you have available and your budget.
Before you do anything else, decide on the site – this will determine the size of greenhouse you can install. Read more about siting a greenhouse.
You’ll also need to decide whether you are able to lay the foundations and build the greenhouse yourself, or whether you will need to get it installed – read more about building a greenhouse.
Once you’ve chosen your greenhouse, you’ll need some kit – read more about the essential kit for your greenhouse.
But now, you have the exciting prospect of choosing a greenhouse! Read on for our advice.
Greenhouses come in a range of widths and lengths, in 2′ increments. It’s best to go for one that is at least 6ft wide; 8ft wide will enable you to put staging (shelves) on both sides. The eaves should be at least 1.5m (5ft) tall to let in plenty of light. Most gardeners wish they had a bigger greenhouse, so choose the biggest you can afford and have room for.
There are three main greenhouse shapes – traditional, lean-to and octagonal. Newer shapes such as domes are also available. Lean-tos takes advantage of an existing wall, for example a south-facing house or garage wall. The bricks hold the heat of the sun, especially at night, ideal for growing. An octagonal or dome shape is useful if you have an awkward space.
Aluminium is cheap, low maintenance and can be powder-coated in a range of colours. Timber, usually cedar, is attractive but more expensive, and needs more upkeep. It is better at maintaining a constant temperature. Wooden models can be glazed to the ground but can also be half-walled with timber or bricks. This holds heat well but means you can’t grow plants at ground level.
Horticultural glass lets in the most light, is long lasting and is easily replaced if broken. Toughened glass is more expensive but a better option in high-traffic areas or if you have kids. It still breaks, but shatters more safely. Polycarbonate is cheaper, doesn’t break and has better insulation properties, but lets less light through and can pop out of its frame in high winds.
Ventilation is essential in summer. Ideally, a 6ft x 8ft greenhouse would have two hinged roof vents, as well as a side vent. It is worth paying for an automatic vent opener, or you can fit your own. Find out how to install an automatic greenhouse vent opener.
A firm, level floor, such as paving slabs or gravel on top of hard core and sand, allow for easy access and drainage and can be wetted in summer (damped down) to keep the air humid. A soil border, is a good way to grow greenhouse crops.
Alternatives to a greenhouse
- A polytunnel is cheaper but less attractive option but a good way of growing summer crops such as tomatoes, and winter crops such as lettuce. It doesn’t hold heat well in winter, so won’t give enough protection for tender winter plants. Find out how to build a polytunnel.
- A cold frame is used to supplement a greenhouse – hardening off plants, taking cuttings and shielding plants from the worst of the winter weather. It can also be used for sowing seeds that need cool conditions and gives good protection for winter lettuces and salads. Read our step-by-step guide to making a cold frame.
- Mini greenhouses are useful in small gardens. They can be used to raise seedlings or grow crops such as aubergines, peppers and tomatoes.