Greenhouses by category
Polycarbonate panels are light, they don't shatter and they hold heat better than single glazing. That makes them the safe pick for gardens with children, pets or footballs. Panel thickness matters most: 4 mm is fine for summer crops and seedlings, 6 mm and up keeps the frost off in spring and autumn.
Glass lets in the most light, stays clear for decades and looks the part in a British garden. Check the glass type before you buy: horticultural glass is cheaper but breaks into sharp shards, toughened safety glass breaks into small blunt pieces.
A lean-to sits against a wall. The brickwork soaks up heat during the day and gives it back at night, and you lose less of the garden. A south or west facing wall suits it best.
A polytunnel gives you the most growing space for the money, which is why you see so many on allotments. The cover lets light through evenly and keeps the rain off. Expect to replace the polythene every few years, and dig the edges in well before the first winter gale.
A growhouse is a shelved frame with a zip-up cover. It fits on a patio or balcony and keeps rain and cold wind off tomatoes, chillies and trays of seedlings. Tie it to a wall or weigh it down, because a gust will tip an empty one over.
A cold frame starts your season four to six weeks early. Lettuce, radishes and hardened-off seedlings do well in it from March. Look for lids that stay propped open and for panels rather than thin plastic.
A 6x4 greenhouse fits in most gardens and still takes a staging bench plus a row of tomato plants. In England a greenhouse this size usually counts as permitted development, so you won't need planning permission unless you live in a listed building or a conservation area.
6x8 is the most popular greenhouse size in the UK. You get room for staging down one side, a border for tomatoes and cucumbers down the other and a path in the middle. Most bases and staging kits are sold to fit it.
From 8x10 you can fit beds on both sides, staging at the back and still turn round with a watering can. Keep it under 2.5 m high if it sits within 2 m of your boundary, and check the permitted development rules before you order.
Under £300 you get walk-in greenhouses with 4 mm polycarbonate, small polytunnels and growhouses. Budget for a base as well, because light frames need anchoring against the wind.
Up to £600 you find branded aluminium greenhouses with thicker polycarbonate or horticultural glass and a maker's guarantee. This is where most home growers end up spending.
From £1,000 you get toughened glass or thick panels, frames built for snow load and often a base in the box. A greenhouse at this level stands for twenty years or more.