The cheapest greenhouse that isn't a waste of money

There is a real cheap greenhouse and there's a fake-cheap greenhouse. The €60 PVC-and-zip-cover thing at the garden centre is the fake. It lasts one season and you replace the cover by year two. The honest floor for something that survives a winter is about €250. I'm on my third greenhouse in four years. Here's what I'd buy if I were starting over.

What the €60 walk-in greenhouse actually is

A walk-in zipper greenhouse is a powder-coated steel frame with a clear PE plastic cover that ties on with ropes. The cover lasts one season — UV degrades it visibly by August. The zipper teeth pull out of the plastic by the second open-and-close. The frame itself is fine if you stake it well, but the cover replacement is €40 and you'll do it annually. Two years in, you've spent €140 and own something flimsy.

If your only goal is to start seeds in March and shelter tomatoes in October, this is acceptable. Stake the corners with 12-inch heavy-duty tent stakes instead of the included pegs, weight the base with paving slabs, and accept you're buying a one-season tool. Don't put €200 of plants in it and expect them to survive a wind event over 50 km/h.

The €250 polycarbonate that actually holds up

The honest entry-level greenhouse is a 6x4-foot aluminium frame with 4mm twin-wall polycarbonate panels. I have a 6x4 aluminium polycarbonate greenhouse that cost about €280 in 2022 and it's still on its original panels. The frame is light enough that one person can assemble it in an afternoon. The polycarbonate diffuses light better than glass, doesn't shatter, and the twin-wall insulates well enough that I get six extra weeks of growing on each end of the season.

What this size won't do: fit a tall human comfortably (you'll stoop), hold a full tomato crop and a propagation bench at the same time, or survive a sustained gale without anchoring. Anchor it. Bolt the base to a paving-slab foundation or concrete pad. The wind will lift an unanchored greenhouse and fold it. Ask anyone who's owned one.

The 8x6 jump that's worth doing if you can

If you cook from your garden seriously, jump to an 8x6 instead of a 6x4. The footprint difference is small; the usable interior is almost double. An 8x6 aluminium greenhouse runs €450 to €600 and gives you a centre aisle wide enough to wheel a barrow into. That matters more than the square footage spec sheet implies.

Don't go bigger than 8x6 unless you have a real plan for the space. Heat management becomes a problem at 10 feet wide — you need automatic vent openers and shading in summer or you cook the plants. Stop at 8x6 unless you're running a serious propagation operation.

The accessories that actually matter

An automatic vent opener at €35 each is the single best upgrade. It uses wax expansion to open the roof vent when interior temperature passes about 18°C. No power, no batteries. Buy two — one for the roof vent, one for the side vent if your model has one. The greenhouse will cook tomatoes in May without these.

A min/max thermometer at €15 tells you what's actually happening overnight. You'll be surprised how warm it stays in October and how cold it gets in late March. Adjust planting accordingly.

A 50% shade net at €20 keeps July from burning the leaves on anything heat-sensitive. Drape it over the roof from June to August. Skip the white shading paint that gets recommended in older books — it's a mess to apply and a worse mess to remove.

The cold frame nobody tells you to start with

Before you buy any greenhouse, consider a wooden cold frame for €90. It's a knee-high box with a hinged glass lid that sits flat against the soil. It does not give you tomato-and-cucumber space. It does give you four extra weeks of lettuce, six extra weeks of hardening off, and a place to overwinter herbs. For most gardeners, a cold frame is what they actually need and not what they buy.

I had a cold frame for two years before I bought my first greenhouse. The crops I grew in the cold frame were the same ones I now grow in the greenhouse. The greenhouse adds capacity, not capability, unless you genuinely want tomatoes, cucumbers, or chillies.

Where the savings stop being savings

Under €100 on a greenhouse is a one-season decision. €100 to €250 is the dead zone — you've spent real money on something that still won't last. Either commit to the €60 disposable for short-term seed starting, or jump to €280 minimum for the polycarbonate kit. The middle ground is where regret lives.

The €280 greenhouse I bought four years ago has paid for itself in salad alone. The €60 one before it is in a landfill.