The "what kind of greenhouse do I need" question gets answered too quickly online. The default answer is "an 8×6 freestanding" and the next eight links recommend the same brand of mini greenhouse. But the right structure depends entirely on what you're trying to grow, how much space you've got, and how serious you are about it. A cold frame may actually beat a mini greenhouse for your situation, and often costs less than a freestanding greenhouse.
This piece walks through the four practical categories (cold frames, mini greenhouses, lean-tos, and freestanding) with the honest case for each. We sell freestanding wooden greenhouses (the NORDIC range) so we have a starting position. But we'll tell you when a £40 cold frame is the right answer.
Written by the Waldenhaus team. Reviewed by the Waldenhaus product team. Last updated 7 May 2026.
Cold frame vs greenhouse: which do you need
A cold frame is a low, bottomless glazed box that sits flat on the ground and runs a few degrees warmer than the air outside. A greenhouse is a walk-in structure whose larger air volume holds steadier conditions. Choose a cold frame for hardening off and a handful of early or late crops, and a greenhouse when you want to raise, grow and overwinter under cover through the year. A mini-greenhouse, the slim tiered shelf unit with a zip cover, sits between the two: more sheltered growing room than a frame, far less stable than a walk-in, and best treated as a propagation stand rather than a year-round house.
The deciding factor is air volume. The RHS notes that a greenhouse holds a larger body of air that buffers temperature and humidity, so swings are gentler than inside a cold frame or a small covered unit, where a high surface-area-to-volume ratio produces uneven, fast-changing conditions. That one difference shapes everything below.
| What matters | Cold frame | Greenhouse |
|---|---|---|
| Access | Reach-in, 30–60 cm tall | Walk-in, room to work standing up |
| Warmth | Typically 3–5°C above outside (Horticulture Magazine) | Holds steadier temperatures; the RHS says plants rated H2 or H3 can cope in a cool or frost-free greenhouse over winter |
| Frost job | Shelters alpines from winter wet, overwinters young annuals | Keeps a frost-free minimum so tender fuchsias and pelargoniums come through (RHS) |
| Ventilation | Hands-on lid lifting; overheating and slugs are the real risks | The RHS says winter ventilation is essential to prevent mould and damp, so roof and side vents earn their keep |
| Cost and footprint | £30–£200, 0.6–1.2 m², renter-friendly | Larger footprint, a multi-year investment in walk-in growing |
The honest answer is that serious growers often run both. A cold frame works as the staging post between the greenhouse and the open garden, so the sequence is raise plants inside, harden them off in the frame over about two to three weeks, then plant out. Bear in mind that fleece adds only about 2°C of protection from frost, by the RHS reckoning, and hardening off acclimatises plants rather than making tender ones hardy, so correct timing still matters whichever you own.
Who each suits. Pick a cold frame alone if space is tight, you rent, and you want hardening off plus a few early crops and somewhere dry for alpines. Choose a greenhouse if you want to raise plants from seed at scale, ripen tomatoes and cucumbers, overwinter tender plants and garden in any weather, since the air-volume buffer gives a stability a frame cannot. If you can stretch to both, the greenhouse raises and grows while the frame hardens off, which is how most kitchen gardens end up working.
When the walk-in option is the one you want, our NORDIC greenhouse pairs Swedish pine with twin-wall polycarbonate in a Nordic-inspired design, and the wider NORDIC collection shows the full range of sizes. Ground anchors are standard so no concrete foundation is required; a firm, level base is recommended for stability. Delivery is made to order, free to the UK mainland, usually within one to four weeks.
The four categories at a glance
| Category | Footprint | Price | Use case | Limitations |
|---|---|---|---|---|
| Cold frame | 0.6–1.2 m² | £30–£200 | Hardening off seedlings, winter salads, propagation | No standing room; only for low crops |
| Mini greenhouse / cabinet | 0.5–1.5 m² | £25–£150 | Patio cropping, herb growing, urban balcony | Limited internal volume, light-construction |
| Lean-to greenhouse | 3–8 m² | £600–£3,500 | Wall-mounted use of small gardens, fruit-tree training | Needs suitable south-facing wall |
| Full freestanding | 5–20 m² | £400–£8,000+ | Year-round serious growing, family veg supply | Needs dedicated plot space |
Each of these solves a different problem. The wrong-category mistake is more common than the wrong-size mistake.
Cold frames
A cold frame is essentially a wooden or aluminium box with a sloped glass or polycarbonate lid that opens for ventilation. Internal height typically 30–60 cm. You don't go inside; you reach in.
What it's actually for:
- Hardening off, the standard pre-planting use. Take seedlings raised indoors, put them in the cold frame for 7–14 days to acclimatise to outdoor conditions before final planting out
- Winter salads. A cold frame in southern England can produce continuous winter lettuce, mâche, claytonia, mizuna, and rocket from October to April with no heating
- Propagation, overwintering rooted cuttings, dahlia tubers, geraniums, fuchsias
- Seed germination in spring, which frees up indoor windowsills
What it's not good for:
- Anything that needs vertical room, such as tomatoes, peppers, cucumbers, climbing crops
- Tender perennials in unheated form during very cold spells (it'll freeze inside if outdoor temperatures drop below -8 °C for any length)
- Year-round serious cropping for a household
Realistic cost-benefit:
- £40 secondhand wooden cold frame plus £20 of bubble wrap for the lid in midwinter equals season-extension that genuinely repays in salad alone
- £150 well-made aluminium cold frame with auto-vent is a 10-year tool if treated reasonably
When to choose a cold frame over a greenhouse: tight budget, tight space, primary use is hardening-off plus winter salads plus propagation. Many serious gardeners run a cold frame in addition to their greenhouse for exactly the propagation use, even when budget for a greenhouse exists.
Mini greenhouses (cabinets, walk-in cubes, lean-up units)
The "mini greenhouse" category covers a big range, from small four-shelf metal frames covered in PVC up to cube-shaped walk-in units about 1 m × 1 m × 1.9 m tall.
What you're typically buying at this size and price:
- 4-tier metal-frame staging covered in clear PVC sheeting (£25–£50)
- Aluminium-frame cube greenhouse with thin polycarbonate panels (£80–£200)
- Wall-leaning pop-up greenhouse with zip-down door (£40–£100)
What it's good for:
- Patio growing, where you have hard standing, no soil, and want to grow tomatoes, chillies or herbs in pots
- Urban / balcony, with a minimal footprint, light enough to move
- Adjunct to indoor growing, where you start seeds indoors and graduate them to the mini greenhouse before final planting (similar to cold frame use)
- Trial year, finding out whether you'll actually use a greenhouse before investing in a real one
What it's not good for:
- Exposure to British storm conditions. The lightweight construction is genuinely vulnerable to UK winds; expect to weight or anchor it down, and to bring covers off in autumn
- Year-round use. The polycarbonate panels are typically thin (1.5–2 mm) and yellow within 2–3 years; the frame is light enough that it racks under load
- Producing meaningful crop volumes. The internal volume is too small to sustain a household's salad supply, never mind tomatoes
Realistic ownership horizon: 2–4 years before the cover degrades and the frame is racked. £30–£40 a year of capital cost.
When to choose a mini greenhouse over a cold frame: you specifically need vertical room (you want to grow upright crops in pots) and don't have garden space for a freestanding structure. Flat balconies and patio-only households are the genuine sweet spot.
Lean-to greenhouses
A lean-to is a half-greenhouse mounted against a south-facing wall, three glazed sides plus the wall itself as the fourth. Internal footprint typically 3–6 m². Internal height matches a normal greenhouse.
What it's good for:
- Small gardens, where it uses a wall that would otherwise be unused and leaves the garden footprint free
- Walls with thermal mass, where a south-facing brick wall absorbs heat during the day and releases it at night, naturally extending the growing season by 2–3 weeks compared with a freestanding structure
- Fruit tree training, where peaches, apricots, figs, and grapes can be wall-trained inside a lean-to with significantly better fruiting in UK conditions
- Visual integration, where it looks like part of the house rather than a standalone garden building, important in some neighbourhoods and conservation areas
What it's not good for:
- Houses without a suitable south-facing wall (north-facing lean-to is functionally not worth doing)
- Renters (usually requires permanent attachment to the building)
- Very tall crops (wall-side height is fixed by the wall mounting)
Cost: budget lean-tos start around £600 (lightweight construction, similar to mid-tier cabinets); proper wooden lean-tos in tier-2 construction grade run £1,400–£2,500. Top-tier lean-tos at tier 3 spec run £3,000–£5,000.
Waldenhaus NORDIC is freestanding gable only: we do not make a lean-to. On an open plot a freestanding NORDIC gives more usable growing space than a wall-mounted lean-to of the same footprint; if a south-facing wall is your only spot, a specialist lean-to may suit better.
When to choose lean-to over freestanding: you have a south-facing wall plus limited garden footprint, or you specifically want fruit-tree training, or your aesthetic preference is for the house-integrated look.
Freestanding wooden greenhouses
The default category and the one most people picture when they say "greenhouse". Footprint typically 5–15 m². Walls all around, ridge roof or apex, door at one end, vent in the roof.
What it's good for:
- Year-round serious growing, where you start seeds in February, overwinter tender perennials, harvest tomatoes through October, salads through winter
- Family veg supply, where an 8×10 ft greenhouse comfortably supplies one or two adults with summer salads and tomato production for 4–5 months of the year
- Plant collections, where fuchsias, alpines, citrus and geraniums all over-winter happily
- A serious permanent garden investment, typical lifespan 15–30 years with mid-tier construction
Five sizes that genuinely work for different households:
- 8×6 ft (~4.5 m²), solo grower, flat or small garden, herbs plus salads plus a few tomato plants
- 8×10 ft (~7.5 m²), family of 2–3, summer veg supply plus winter salads plus propagation
- 8×13 ft (~9.7 m²), serious hobby growing, two ground beds plus central path plus staging
- 8×16 ft (~11.9 m²), established gardeners, multi-crop year-round
- 8×20 ft (~14.9 m²), walk-in market growers, near-commercial scale
The full sizing question is in our What size greenhouse do I need guide.
Decision matrix: which one for you
Five questions to find your answer:
Q1: How much garden space have you got dedicated to this?
- Under 1 m²: cold frame or balcony mini greenhouse
- 1–3 m²: mini greenhouse or lean-to (if wall available)
- 3–10 m²: lean-to or 8×6 freestanding
- 10–20 m²: 8×10 to 8×16 freestanding
- 20+ m²: 8×16 to 8×20 freestanding
Q2: How serious is the growing ambition?
- Hardening off plus winter salads only: cold frame
- Patio cropping a handful of plants: mini greenhouse
- Family veg supply: 8×6 freestanding minimum
- Year-round serious cropping: 8×10 freestanding minimum
- Near-commercial volume: 8×16 freestanding minimum
Q3: Do you have a south-facing wall available?
- Yes, with 3+ m of run, no obstructions: lean-to is genuinely worth considering
- No, or only a poor wall: skip lean-to, go freestanding
Q4: How long will you be at this property?
- 1–3 years: cold frame or mini greenhouse (low cost, walk-away friendly)
- 3–10 years: 8×6 to 8×10 freestanding (good investment horizon)
- 10+ years: 8×10 to 8×20 freestanding (full ROI window)
Q5: What's the realistic budget?
- £30–£200: cold frame or mini greenhouse
- £600–£1,800: lean-to or mid-tier freestanding (this is where NORDIC sits)
- £2,000–£4,000: top-tier British wooden greenhouse, freestanding or lean-to
- £4,000+: heritage glasshouse territory
The honest answer for most UK households interested enough to read 1,500+ words on greenhouse choice: an 8×10 ft freestanding wooden greenhouse, mid-tier construction grade, on a properly anchored base, is designed to last 20+ years and produces meaningful annual crop. That's the rational sweet spot. Cold frames and mini greenhouses are useful complements, not replacements.
Why these categories fail people who choose wrong
Three specific situations worth flagging:
Choosing mini greenhouse when cold frame would be better. £80 spent on a cube greenhouse that gets used twice a year for hardening off; the same use is served better by a £40 secondhand cold frame. The mini greenhouse takes patio space, looks tatty after two years, and gets discarded.
Choosing lean-to when freestanding would be better. Lean-to bought because the garden is "small" but actually has plenty of room for a freestanding 8×10. The wall used isn't quite south-facing, so the heat gain advantage doesn't materialise. The structure ends up performing like a small freestanding greenhouse but at higher cost. Freestanding 8×10 in the same garden would have given more space and more light.
Choosing 8×6 freestanding when 8×10 would be better. "I'll start small and upgrade later" is rarely how it plays out. The 8×6 fills up within one season, the buyer wishes they'd bought bigger from the start, and second-hand 8×6 greenhouses don't sell well so it's a sunk cost. If the budget will stretch and the garden has room, going to 8×10 from the start is almost always the better call.
Frequently asked questions
Is a cold frame really enough for serious growing?
For year-round serious cropping, no. A cold frame doesn't have the volume for tomato production or anything tall. For seed-starting, hardening off, and winter salads, it is enough, and often better than a greenhouse for those specific uses (more thermal stability, lower running cost, easier to manage). Many serious gardeners run both: cold frame for propagation, freestanding greenhouse for cropping.
Can I put a mini greenhouse in a windy garden?
Genuinely not advisable. The lightweight construction is the category's main weakness; strong UK gusts regularly damage cube and 4-tier mini greenhouses. If you're in a sheltered urban setting, fine. Anywhere with regular exposure to British storm conditions: a cold frame or a proper freestanding structure handles it; a mini greenhouse will fail.
Do lean-to greenhouses lose less heat than freestanding?
Slightly, yes. The wall-side has substantially better insulation than glazing, so total heat loss surface is reduced. The thermal-mass effect of a south-facing brick wall also adds a 2–3 °C overnight buffer. Real-world running cost saving: 20–30% compared with an equivalent freestanding greenhouse in the same garden.
What about polytunnels, where do they fit?
Polytunnels are a separate category: large-volume covered growing space with single-skin polythene sheet glazing. They're cheap per m², but have shorter service lives (cover replacement every 3–5 years), don't hold up well to British storm conditions over time, and don't look like a permanent garden feature. The full polytunnel comparison is in our polytunnel vs greenhouse guide.
How long do mini greenhouses actually last?
Typically 2–4 years for the lighter-construction cube and 4-tier types; 5–8 years for solid aluminium-frame mini greenhouses with twin-wall polycarbonate. The covers are usually what fail first (UV degradation), not the frames.
If I buy a cold frame now, will I outgrow it?
Probably yes if you start growing seriously. Most people who get into gardening through a cold frame upgrade to a freestanding greenhouse within 2–3 years. But the cold frame keeps its place even after the upgrade: it's the propagation tool. Few serious gardeners ever discard their cold frame.
What's the smallest freestanding greenhouse worth buying?
We make our smallest freestanding NORDIC at 8×6 ft (£1,499). At that size you have full standing room, two staging areas plus central walkway, room for an 8-pot tomato planting, and a real growing season-extension capability. Going smaller than 8×6 starts to overlap with cold frame territory at greenhouse cost, not the right trade-off for most situations.
Choose your NORDIC wooden greenhouse
By size
- 8×6 ft, NORDIC-S £1,499 · patio / starter / small allotment
- 8×10 ft, NORDIC-M from £1,599 · family veg garden sweet spot
- 8×13 ft, NORDIC-L from £1,699 · serious year-round growing
- 8×16 ft, NORDIC-XL from £1,799 · multi-crop with two ground beds
- 8×20 ft, NORDIC-XXL from £1,899 · walk-in / market grower
By configuration
- Polycarbonate greenhouses UK · 4 mm CrystalLight glazing detail
Decide before you buy
- Greenhouse Buying Guide UK 2026 · full step-by-step framework
- Wooden Greenhouses overview · the NORDIC range explained
- Shop the NORDIC range, from £1,499
See also: Small Wooden Greenhouse: NORDIC S, the proper compact alternative to mini cabinets
