Greenhouse Buying Guide
June 24, 2024

If you love growing your own crops in your garden or allotment, buying a greenhouse is the ideal next step. An excellent asset in any gardener’s arsenal, it’ll allow you to grow so much more, both during the warmer months and over winter, so you can reap bigger and better rewards all year long.  Our experts here at Robert Dyas certainly know a thing or two about these great garden buildings, so we’ve created this guide with their advice to provide you with everything you need to know before choosing your perfect greenhouse.

What Is a Greenhouse?

A greenhouse is a heat-retaining garden building that protects plants – commonly vegetables – and exotic species from colder outside temperatures all year round. They keep the heat in so that you can extend the growing season, bringing some plants on early and allowing others to continue cropping untroubled until well into the autumn and even winter. They keep out frost during winter, usually maintaining a temperature of 5 degrees above the temperature outside, so are the perfect place for delicate or exotic plants, or hardy herbs and salad crops. They’re usually made entirely of glass to let in as much light as possible to produce thermal energy for the plants to thrive in, though some types are made from plastic and work just as well. 

It’s very easy to incorporate a greenhouse into a garden – if your space is large you simply need to choose the right zone; if it’s small you can either go for a compact design or a budget-friendly grow house.

What Can I Grow in a Greenhouse?

There are lots of crops you can grow in a greenhouse, making them great for gardening activities with younger children as well as mature gardeners. Common greenhouse plants are: 

  • Tender crops such as tomatoes, peppers, chillies, aubergines and cucumbers throughout summer.
  • Exotic plants that love heat like melons and sweet potatoes.
  • Salad crops like lettuce can make use of the autumn sun for an extended growing period. Some hardy types will even grow over winter. 
  • Hardy vegetable plants like kale and Brussels sprouts can be started off earlier than outdoors.
  • Potatoes, which may otherwise be affected by adverse weather conditions or frost. 

Do Greenhouses Need Planning Permission?

Planning permission is not generally required for a greenhouse. It’s only required if the building is greater than 50% of the total land around the house, which is highly unlikely for a greenhouse. 

How to Find Your Perfect Greenhouse

To find the ideal greenhouse for your space, it’s important to first consider the area it will sit in. The best place is the sunniest spot so your plants can make the most of all that extra light and warmth.  

For new gardeners, a small greenhouse is perfect for housing a selection of vegetables and plants to complement your outdoor kitchen cooking, such as tomatoes for al fresco salads and pizzas or salad crops that last well into the autumn. You could opt for a small cold frame to start off crops early and overwinter them. Or you could choose a specific tomato grow house for tender plants like aubergines, cucumbers and of course tomatoes, which take up less space than a regular greenhouse. These can be packed away over winter to save space when not in use. If your garden is medium-sized, you could choose a lean-to design which has one open side that fits against a wall of your house to take up less room. 

For more seasoned gardeners, a larger greenhouse would be more suitable. Walk-in designs offer lots of space to tend your plants, with plenty of shelves for your pots and a strong and durable design. Many greenhouses these days come with virtually unbreakable polycarbonate panels which are impact-resistant and withstand extreme weather conditions.

Another option is a potting shed which combines a greenhouse and shed so you can enjoy the best of both worlds. 

Where To Put a Greenhouse in a North-facing Garden

A north-facing garden is least ideal for a greenhouse but you will get a good amount of evening sun in the summer months from May to October. Use a sun map to see where the sunniest spot in your garden is, make sure it’s not in a frost pocket or exposed to cold winds, and line up the ridge of the structure to run east to west to maximise light. It’s best to choose plants that don’t require a huge amount of sunlight if your greenhouse will often be in shade. 

Make sure you don’t position your greenhouse under trees as they’ll block the sun and disperse debris over the glass, making it even shadier. The roots can also disturb the foundations and branches could fall and smash the glass – a costly problem you want to avoid! 

The Different Types of Greenhouses

There are several different types of greenhouses to suit each space which we’ll list below.

Traditional greenhouse

The classic walk-in glass greenhouse with a metal frame for those with plenty of space.

Lean-to greenhouse

These designs fit against a wall of your house so as not to take up too much room.

Round/hexagonal greenhouse

A quaint design with a charming aesthetic that fits well in oddly shaped spaces.

Wooden greenhouse

Wooden greenhouses are either large or small. Small designs are essentially like wooden-framed glass cupboards for those with limited space, while large designs give a more rustic charm to bigger gardens.

Potting shed

Potting sheds are a combination of a shed and greenhouse to give you the best of both worlds. They have a side of angled glass to enable plants to get the maximum amount of light.

Cold frames

These small structures are for starting plants off early to extend the growing season.

Portable greenhouse

A portable greenhouse, or grow house, is a more budget-friendly option. It’s a temporary structure that can be stored away when not in use during winter.

How to Build a Greenhouse

Many greenhouses, including those we sell here at Robert Dyas, require self-assembly with the instructions provided. While each greenhouse assembly is unique, we recommend laying each piece out before starting so you can start the task with a clear idea of what pieces you have and which ones will be going where. 

It’s vital to set your greenhouse on a properly prepared base to avoid any problems later on, such as having to fork out for costly replacement glass or even a new greenhouse!  Most greenhouses come with a separate metal frame base that can be secured before building the rest of the frame. Suitable bases to build your greenhouse on include perimeter bases made from breeze blocks, paving slabs or concrete; a full base of paving slabs; or, the most durable of all, a concrete base. 

Once your base is prepared, build the structure first and use a spirit level to ensure the frame is straight. Then proceed with care when adding the glass panels, making sure you wear safety gloves in case of accidental breakages.

Caring & Cleaning for a Greenhouse

Keeping your greenhouse clean is important for the productivity of your plants. Whether it’s glass or plastic, a thorough clean will remove any moss, algae and grime on the glass to let in more light, and it also helps to control pests and diseases.

Choose a dry, calm day and firstly remove your plants. Then brush or clear away all debris, clean the structural parts with disinfectant or detergent, and wash the glazing both inside and out. Make sure you choose an appropriate greenhouse cleaning solution that won’t affect the plants. If you added shade paint during the summer, wipe it off in winter to let in the light. 

 

When the weather starts to turn a bit cooler, shut greenhouse vents, doors and windows after dusk to retain heat overnight. Open them up in the morning to avoid a build-up of heat gained during daylight hours.

Make sure greenhouse heaters are in good working order ahead of first frosts and replace them if necessary.

Around November time, add some insulation to your greenhouse to keep plants nice and warm throughout the winter. Cut some greenhouse bubble wrapping into pieces and fix it into place with plastic clips that fit into the grooves between the glazing bars.



If you can’t wait to get going with your greenhouse growing, start looking for the right type for your space in our extensive range. Whether you opt for a traditional type, potting shed or a space-saving cold frame or grow house, the seasons will soon be so much more rewarding.