Greenhouses

Greenhouses: Your Garden's Best Investment, Measured in Tomatoes

At some point, every keen gardener has the same thought: if only I could start things earlier, protect the tender stuff, and actually grow things that need more warmth than a British summer reliably provides. That thought usually leads, one way or another, to a greenhouse. And once you've had one, it's genuinely difficult to imagine gardening without it.

A greenhouse extends your growing season at both ends — you're starting seeds in February, hardening off plants in March, and still harvesting tomatoes in October when everything outside has gone over. It's shelter, warmth, and control all in one structure, and for a lot of gardeners it's the single biggest upgrade they make to how their garden actually produces.

Glass vs Polycarbonate — The Big Decision

Most greenhouses use either horticultural glass or polycarbonate panels, and the choice affects everything from heat retention to price to longevity.

Glass is the traditional choice and remains excellent — it gives better light transmission than polycarbonate, it doesn't discolour over time, and a well-maintained glass greenhouse looks genuinely beautiful. The downsides are weight, fragility, and the fact that glass loses heat faster at night. Toughened glass addresses the safety concern and is worth specifying.

Polycarbonate (usually twin-wall or triple-wall) offers better insulation than single glass, is lighter, and won't shatter if a plant pot falls against it. The light transmission is slightly lower, and the cheaper versions do yellow and become brittle after several years in UV. Opt for UV-stabilised polycarbonate and the lifespan improves considerably. For year-round use in the UK, the insulation advantage of twin-wall polycarbonate is a genuine practical benefit.

Size: Bigger Than You Think You Need

This is the piece of advice every greenhouse owner gives with the benefit of hindsight: buy bigger than you think you need. The standard 6×8 foot greenhouse feels spacious in January and cramped by June. An 8×10 or 8×12 gives you room to actually move around, have a potting bench, and grow vertically as well as along the staging. If your budget and space allow for it, always go up a size.

Lean-to greenhouses attach to a house or garden wall and make excellent use of limited space, with the added bonus that the wall retains heat. They're ideal for south or west-facing walls. Freestanding models give you more flexibility in positioning but need to be oriented with the ridge running east to west for maximum light.

Structure and Frame

Aluminium is by far the most common frame material — it's lightweight, doesn't rot, and requires virtually no maintenance beyond an occasional wipe down. Powder-coated aluminium in green or black has become increasingly popular for gardens where the greenhouse is a visible feature, and it does look considerably better than bare silver aluminium in a traditionally planted space.

Timber frames — cedar especially — are beautiful and well-insulated, but they need treating every two to three years or they'll eventually rot at the base. The maintenance trade-off is worth it for some people; for others, aluminium's zero-maintenance appeal wins easily.

What to Grow

The obvious candidates are tomatoes, cucumbers, peppers, and aubergines — crops that need warmth British summers can't reliably provide. These thrive in a greenhouse and can produce impressively all season. Beyond the obvious, a greenhouse extends what's possible enormously: chillies, melons, peaches trained along the back wall, overwintered tender perennials, early broad beans and lettuce in February.

For seed starting, a greenhouse is invaluable. Combined with decent gardening tools and a good irrigation system, you can run a genuinely productive growing operation that extends well beyond what's achievable outside.

Ventilation and Temperature Management

This is the bit beginners underestimate. A closed greenhouse in July can reach 50°C on a sunny day — enough to kill everything inside within hours. Roof vents are non-negotiable; automatic vent openers that respond to temperature are one of the best small investments you'll make. Ideally you want roof vents on both sides of the ridge and sufficient total vent area to equal at least 20% of the floor area.

Shading (either shading paint or internal blinds) helps manage summer temperatures. Heating for winter growing can be as simple as a small electric fan heater on a thermostat, which keeps frost at bay without excessive running costs.

Accessories and Add-Ons

Staging — the slatted shelving that runs along the sides — is almost always worth including. It gives you growing space at a comfortable working height and improves air circulation around plants. A potting bench at one end makes the greenhouse a proper workspace rather than just a growing space. Guttering to collect rainwater into a butt inside or outside is worth fitting from the start.

Take a look at plant accessories for the internal setup — pots, trays, propagators, and support systems that make greenhouse growing more efficient. And for the space around the structure, garden storage nearby keeps compost, canes, and seasonal equipment tidy and accessible.

Choosing Your Greenhouse

The range in quality between greenhouse brands is substantial, and it's worth taking time to compare before committing. Our brands directory lists greenhouse specialists across different price points, from entry-level polycarbonate models to serious timber and glass structures built to last decades. Check the deals section too — greenhouse prices vary seasonally, and late autumn often sees good reductions as demand drops.

A greenhouse is genuinely one of those additions that changes not just what you grow, but how you feel about the garden. It turns it into something you can engage with year-round, in all weathers, at any time of year. That's worth a lot.