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How to buy the best greenhouse

Our expert greenhouse guide reveals the different types of greenhouses, typical prices, sizes and how to pick the best heater
Which? Team

A greenhouse is a major investment for your garden and one that’s not easy to move or replace once installed, so it's important to pick the right one for your needs. Our expert guide tells you everything you need to know.

Whether you're shopping for a small greenhouse to protect young plants or a larger alternative to work on fruit and veg, we can lend a helping hand. On this page, we've rounded up details on optimal materials and sizes, features to look out for, greenhouse accessories and heaters.

Keep scrolling for an overview of popular greenhouse types, plus our top tips on how to build a greenhouse for yourself.

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Types of greenhouses

Freestanding greenhouses

Freestanding greenhouse

Pros: Lets in light from all sides, lots of choice, often roomy enough to work in

Cons: Can lose heat as all sides are exposed, you will have to find a way to get power to it

Freestanding greenhouses are often made from wood, aluminium or PVC. They are usually square or rectangular with an apex roof.

Most gardeners will opt for a 6 x 8ft (1.8 x 2.4m) or 8 x 10ft (2.4 x 3m) model. Think about freedom of movement and what you plan to grow when determining the ideal size – you might need double doors to move plants in and out, for example.

Freestanding greenhouses allow light in from all four sides, although this means they're more exposed to the elements compared to other greenhouse types. You can install bubble insulation if needed. As these greenhouses can be quite large, you might also want to run electricity to the space so you can see in low light.

When deciding where to position your freestanding greenhouse, consider which parts of your garden get plenty of sunshine. You also need to think about the impact of strong gusts of wind and whether the building is well-protected.

If you need additional space for your gardening equipment, check in with our guide on how to buy the best outdoor storage.

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Lean-to greenhouses

Lean-to greenhouse

Pros: Wind resistant, maximises unused space, can be particularly energy efficient

Cons: Not as much space to plant a variety of crops, fewer sides for light to enter

If you're shopping for a greenhouse that isn't exposed to the elements from every angle, consider a lean-to greenhouse. These join to an existing structure, such as a house or garage (shown above).

These greenhouses are a popular choice among gardeners working with limited space in their backyard, or those that want a greenhouse closer to their home. Having your greenhouse within a shorter distance means you don't need to run water and electricity across the full length of your garden.

Lean-to greenhouses are often made from wood, although this needs to be maintained over the years, making aluminum a tempting alternative. The initial purchase costs are similar to a freestanding model, but a lean-to takes up less space and you only need access around three sides. It is also cheaper and easier to keep warm.

Mini greenhouses

Mini greenhouse

Pros: Space-saving, cheaper than a full-sized greenhouse, most can be stowed away

Cons: Can be difficult to tend to plants if you have limited mobility, limited growing space

A mini greenhouse is like a glazed cupboard with shelves that sits on a patio or under a window, using a house wall or garage as protection – perfect if space is limited. It will protect trays or pots of young plants from late frosts in spring, and encourage borderline crops such as peppers to ripen.

Ideally, a mini greenhouse should face east or west. South-facing ones overheat in spring or summer unless shaded, and north-facing ones suit only shade-loving plants.

Mini greenhouses are generally easy to set up and maintain, making them well-suited to both newbies and experienced gardeners. Some feature built-in grow lights, and many models can be dismantled and repositioned (or stored away) when needed.

We've used greenhouses to trial a selection of tomato varieties – see the full results with our guide on how to grow tomatoes.

Wooden vs aluminium greenhouse frames

Most greenhouse frames are made of aluminium. Wooden greenhouses are also available, though, and many gardeners find them more attractive to look at, despite the fact they need more maintenance compared to metal frames.

Aluminium greenhouses

Aluminium greenhouse

Pros: Budget-friendly, durable, plain silver is maintenance-free, light and easy to assemble

Cons: Fastenings needed to attach shading material, tricky to extend, insulation can be poor, usually need to add your own base

Aluminium is the most common material for greenhouses, which means you’ll be spoilt for choice. These models are available in a variety of shapes and sizes, so you'll have some options that suit your budget.

Generally speaking, aluminium greenhouses are considered low maintenance as they're able to withstand harsh weather. Aluminium won't warp or crack over time, and the material is rust-resistant. A lightweight metal construction also ensures the greenhouse is easy to move or dismantle.

Wooden greenhouses

Wooden greenhouse

Pros: Can stain to a specific colour, easy to attach shading material, better insulation

Cons: Can be expensive, usually need to add your own base (keeping the wooden frame off the damp ground), vulnerable to rust, needs regular maintenance

Wooden greenhouses are less common and typically cost more than their aluminium counterparts. Picking the right type of wood will help avoid a greenhouse that’s vulnerable to rot. Softwoods, such as deal (pine), are vulnerable to rot, even if the timber has been treated.

Wood is a natural insulator, so it should retain heat fairly well once winter rolls around. You can add additional insulation panels to your wooden greenhouse if needed.

Naturally durable timber – usually western red cedar – can be left to age to a silver-brown. For looks, a western red cedar greenhouse is hard to beat. Look for manufacturers that offer a guarantee against rot.

For gardeners working with a limited budget, be aware that you'll usually need to add your own base to a wooden greenhouse.

If you think you'd benefit from adding a shed to your garden, consult our in-depth guide on how to buy a shed.

Are plastic greenhouses any good?

Glass is the main glazing material used in greenhouses, hence the alternative name ‘glasshouse’. Horticultural glass is inexpensive and easily replaced, but if you're concerned about breakages or safety, you can opt for a plastic greenhouse.

Plastic greenhouses have twin-walled polycarbonate sheets. Polycarbonate greenhouses let in sufficient light for plant growth initially but, over the years, they can become cloudy and age poorly. Toughened glass is a better option, particularly if the greenhouse is on show.

Plastic greenhouse

Toughened or safety glass is stronger than horticultural glass and, if it does break, the resulting pieces are not so sharp. Choosing this option adds about £200 to the cost of a small greenhouse.

Another option is a self-adhesive safety film – this is a transparent film applied to horticultural glass. If the glass is subsequently broken, the film holds the fragments together. However, as the film does not reduce breakages, it could end up more expensive than choosing toughened glass from the start.

To find out which products will leave your plants looking good through summer, explore our controlled-release fertilisers reviews.

Cheap greenhouses

If you're shopping for a greenhouse on a limited budget, the most affordable option will be a smaller, aluminium model. You can expect to spend around £200, although prices can rise depending on the quality of the materials used.

Greenhouses on sale for less than £200 are often classed as a 'mini greenhouse' or a 'cold frame greenhouse' – both can easily be moved to a spot in your garden that's well-suited for growing specific plants. Models that allow varying levels of ventilation are popular, as are cold frames that can be set up on gravel or paved areas.

Larger, wooden structures and greenhouses with ready-made shelving and additional accessories can cost anywhere between £1,000 and £4,000.

Discover the best pop-up plastic greenhouses

Where to buy a greenhouse

Both generalist retailers and dedicated garden shops offer a wide range of greenhouses. To make sure you're buying a greenhouse that's safe to use, only shop with trusted sellers online or in-store.

Ideally, you'd get to see the greenhouse in-store before buying. If this isn’t an option, find out as much information about it as possible before parting with your money.

Popular online retailers that sell greenhouses include:

  • B&Q – stocks a selection of greenhouses made from aluminium, metal, plastic and timber. One of the more affordable options is the Outsunny walk-in tunnel at around £130.
  • Greenhouse stores – sells various types of greenhouse including aluminium lean-to models at £300. If you're after an all-wood structure, expect to spend at least £2,600.
  • Rhino – has freestanding and lean-to greenhouses starting at a width of 4ft (1.2m). The majority are available in a range of colours and come fitted with 'toughened glass.'
  • Homebase – prices start at around £120 for a walk-in polytunnel. The retailer also offers metal greenhouses (from around £350) and wooden models (from around £500).
  • Greenhouse people – offers various guarantees, including a '100% refund guarantee' (within 30 days of delivery) and a free, '10-year frame guarantee'.
  • Screwfix – has a small selection of wooden greenhouses, with prices starting at around £3,000 for a 4 x 6ft (1.2 x 1.8m) timber model.
  • South West Greenhouses (Argos) – a mixture of mini greenhouses and walk-in alternatives. If you're shopping for a full-sized metal structure, expect to spend at least £430.
  • South West Greenhouses (Wickes) – the cheapest option is a £45 plastic greenhouse. For permanent alternatives, the retailer has wooden structures starting at around £430.
  • South West Greenhouses (Direct) – a wide range of styles, including wooden greenhouses, aluminium greenhouses, lean-to greenhouses and greenhouse-shed combinations.
  • Hartley Botanic – Large-scale greenhouses for a spacious garden, including the Wisley 8 Grow & Store that has a claimed width of over 8ft (2.4m).

See which retailers are rated highly with our guide on the best and worst shops.

Large greenhouse with lots of plants

Greenhouse sizes

The size of your greenhouse will be limited to what you can fit in your garden. For most of us, it will be fairly modest, especially if you live in a city. Larger structures typically cost more, so even if size isn’t a factor, budget might be.

Your best bet is to opt for the biggest greenhouse you can. Width is an important dimension because this will determine the benches and aisles. Below, we've listed some of the most common greenhouse sizes:

  • Mini greenhouse: 2-3ft (0.6-0.9m)
  • Small greenhouse: 6ft (1.8m)
  • Medium greenhouse: 8ft (2.4m)
  • Large greenhouse: 10ft (3m)
  • Commercial greenhouse: 12-20ft (3.6-6m)

Most people opt for a 6 x 8ft (1.8 x 2.4m) or 8 x 10ft (2.4 x 3m) freestanding greenhouse. This is wide enough for a central path, with shelving on one side to hold a propagator and potted plants, and a greenhouse border on the other side, so tall cropping plants, such as cordon tomatoes and cucumbers, can be planted directly into the soil.

12ft wide (around 3.6m) is a semi-professional width, and anything above this is typical for commercial use.

Greenhouse staging

When settling on a greenhouse size, make sure you can get in and out of the door easily and that you feel comfortable once inside. Note that low greenhouses can feel claustrophobic.

If space is limited, you might want to opt for a mini greenhouse that sits under a window or against the wall.

Fancy upgrading your gardening equipment? Explore our gardening tool reviews.

Greenhouse features and accessories

  • Automatic vent-opener – contains a cylinder of wax that expands and opens in heat, then closes when cooler so you're not reliant on being there to open and shut the vents as the temperature changes. 
  • A watering timer/computer – will allow you to set the water to switch on and off without you needing to be there.
  • Capillary matting – will absorb water when you wet it and gradually release it to plants, so it can help keep plants on staging moist. You'll need a solid base under it, though.
  • Clean labels – are invaluable for identifying what you're growing. These can be cleaned with wire wool or sandpaper at the end of the season, so they can be reused. A pencil is the simplest way of marking them. 
  • Greenhouse vents – you will need at least two vents in the roof and one at the side to give a good flow of air. The number of vents depends on the size of the greenhouse, but consider paying extra for additional ones. 
  • Heated propagator or heated pad – many seeds and cuttings benefit from some extra heat. Look for a model with a thermostat as this will allow you to preset the temperature you would like. Whichever you choose, you'll need an outdoor socket with an RCD to provide the power needed to run them.
  • Irrigation system – to keep the plants watered while you're out. You can run these from the mains or from a water butt using a water-butt pump to move the water.
  • Min/max thermometer – keeping an eye on the temperature of the greenhouse will help you ensure your plants aren't getting chilled or cooked. You can choose from traditional models that sit in the greenhouse or battery-powered ones with a remote sensor whose readings you can view from the comfort of your house.
  • Modular trays – have individual compartments for a number of plants within the same tray and help to avoid root disturbance when you take the plants out. 
  • Potting tray – is a useful accessory as you can stand trays and pots in it while filling them with compost and then simply tip the excess compost back into the bag so it's not wasted. We'd always recommend that you use a Best Buy compost.
  • Recycled pots – if you're concerned about using plastic, either look for recycled pots (many garden centres offer these) or use a soil-block maker which creates blocks of compost to grow your plants in. 
  • Self-watering pots – with a water reservoir. 
  • Shading – shading is important to help keep things cooler. Shading blinds or netting can be fitted outside or inside the greenhouse, or you can paint on a white shading wash, which looks a bit unsightly in the summer but soon washes off. 
  • Shelving or staging – greenhouse shelving, also known as staging, will display plants and provide a surface for you to sow seeds and take cuttings. Both wooden and aluminium staging is available, so you can get the same type as the greenhouse frame. Staging that is easily removed can be useful if you plan to use the floor space later in the season for growing plants in pots or growing bags.
  • Slatted staging – good for letting light through the lower shelves and can encourage good air circulation which can reduce the risk of fungal diseases. 
  • Solid staging – is needed if you want pots to sit on capillary matting to make watering easier. 
Building a greenhouse

Where should I put a greenhouse?

In practice, there are probably only one or two suitable places in your garden, and this will limit the size of greenhouse you opt for – which is why most people end up with a small one. Here are some top tips to help you pick the perfect position for your greenhouse:

  • The greenhouse should be sited where there is plenty of light, but not exposed to high winds.
  • A sheltered spot is good, but avoid placing it under trees.
  • There needs to be access space around the greenhouse for cleaning, as well as room for acclimatising greenhouse-raised plants to the outside (for example, space for a cold frame).
  • A heated greenhouse gives more scope for raising a wider range of seeds and cuttings earlier in the season. The nearer the greenhouse is to the house, the more economical it will be to get electricity to it. You must, by law, hire a professional electrician to do this. 

For a tradesperson you can trust, visit Which? Trusted Traders and find a professional near you. You can also use our Trusted Trader search tool below.

Greenhouse heaters

You'll need an electric fan heater rated at least 2kW to guarantee keeping a standard 6 x 8ft greenhouse frost-free in most parts of the UK.

If you opt for a gas or paraffin heater, it'll need to be about 20% more powerful – this is to compensate for heat lost via the vents left open to allow poisonous gases and water vapour out and oxygen in.

Lining the greenhouse glass with bubble insulation will also help to retain the heat and keep your structure snug in the depths of winter.

Greenhouse heater

Types of greenhouse heaters

  • Electric greenhouse heaters – If your greenhouse has an outdoor socket with an RCD nearby, a thermostatically controlled fan heater is ideal. They're cheap to run and the fan not only helps distribute the heat but also encourages air movement, which in turn reduces the risk of fungal diseases that favour still, damp air.
  • Bottle gas greenhouse heater  If you don't have an outdoor socket, a bottle gas heater with a thermostat is a good option. Bear in mind that they're heavier and bulkier than electric heaters. They're also trickier to switch on and have no fan, so there may be cold spots in the greenhouse, particularly at floor level. 
  • Gas heaters  produce water vapour, so you'll need to leave vents open for it to escape or you could run into problems with fungal diseases. Good ventilation also ensures that the heater doesn't run short of oxygen and start giving off toxic gases such as carbon monoxide.
  • Paraffin greenhouse heater These heaters need to be filled up very frequently and aren't very safe because they are easily knocked over and can be a fire risk.

Popular online retailers that sell greenhouse heaters include:

  • Screwfix – sells the Apollo 77018 paraffin heater, which has a claimed burn time of around 168 hours. 
  • B&Q – stocks a selection of greenhouse heaters with prices starting at around £20.
  • Greenhouse People – the retailer sells electric heaters, gas heaters and paraffin heaters.

Compare gas and electricity prices now using Which? Switch, our independent energy comparison website. check wording of this link

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