Cloches, Fleece & Mini Polytunnels: Cheap Frost Protection That Actually Works
An honest, hands-on guide to the cheapest, most effective ways to shield seedlings and crops from cold over winter and early spring.
Every spring I do the same daft thing. The sun comes out for three glorious days in late March, I get carried away, and I plant out a tray of courgettes or a row of beans that have been pampered on the windowsill for weeks. Then the forecast turns, a clear night rolls in, and the temperature quietly slides below freezing while I sleep. Without protection, that's the end of them — blackened, slumped and beyond saving by breakfast.
The frustrating thing is that frost rarely needs much to be defeated. We're not talking about a heated greenhouse or thousands of pounds of glass. More often than not, the difference between a thriving bed and a wiped-out one is a single layer of fleece or a plastic dome that costs less than a takeaway coffee. In my own beds, the gap between a protected and an unprotected plant on a cold April night has come down to just a couple of degrees — and a couple of degrees is the whole game.
This guide walks through the three workhorses of cheap frost protection: cloches, garden fleece and mini polytunnels. I'll explain how each one performs, where each one falls down, and which I'd reach for depending on what you're growing and how much faff you can tolerate. By the end you should know exactly which to buy, what weight or size to get, and how to use it so your seedlings sail through the cold snaps that catch the rest of us out.
The Three Tools at a Glance
Before we dive into the detail, it helps to understand that these three categories aren't really competing for the same job. They overlap, but each one has a sweet spot. Cloches are individual little greenhouses; fleece is a flexible blanket you can throw over almost anything; and mini polytunnels are a halfway house that turns fleece or polythene into a self-supporting tunnel over a whole row.
The numbers above are worth sitting with for a moment, because they tell you most of what you need to know. Standard 17gsm fleece and a hand-blown glass cloche both buy you roughly 2–3°C. Step up to 30gsm heavy-duty fleece and you're into 4–5°C of protection — the difference between surviving a light frost and shrugging off a genuinely cold night. Everything else is about convenience, cost and how much ground you need to cover.
Garden Fleece: The Cheap, Flexible All-Rounder
If I could only own one frost-protection product, it would be a roll of horticultural fleece. It's the cheapest, lightest and most versatile of the three, and it's the one I reach for ten times more often than anything else. Fleece is a soft, fibrous, translucent sheet — UV-stabilised polypropylene — that you simply drape over plants or wrap around them. It's permeable to air, light and water, which is the crucial bit: you can leave it on for days at a time, rain will pass straight through, and the plants underneath keep breathing.
The way it works is gentle but effective. The fleece traps a thin layer of slightly warmer air around the foliage and slows the radiation of heat from the soil into a clear night sky. It's that radiant heat loss that does the damage on frosty nights, and even a flimsy barrier reduces it dramatically.
Which Weight Should You Buy?
Fleece is sold by weight in grams per square metre (gsm), and the weight is the single most important spec to understand. Heavier fleece protects more but blocks more light, so there's a genuine trade-off rather than a "bigger is better" situation.
| Fleece Weight | Frost Protection | Light Transmission | Best Use |
|---|---|---|---|
| 17gsm (standard) | 2–3°C | ~80% light through | Leave on growing crops, light frosts, pest barrier |
| 30gsm (heavy-duty) | 4–5°C | Blocks ~30–40% of light | Hard frosts, short-term overnight cover |
| 45gsm (heavy-weight) | Higher than 30gsm | Most light blocked | Tunnels, harshest conditions, tender plants |
For most gardeners, the standard 17gsm is the workhorse. Because it lets about 80% of light through, you can leave it draped over a bed for weeks without the plants etiolating (going pale and leggy from lack of light). That makes it brilliant for newly sown carrots, beetroot and salad leaves, where you want continuous gentle protection and an extra benefit: it keeps carrot fly and other pests off too.
The heavier 30gsm fleece is a different beast. It gives you a meatier 4–5°C of protection, which can be the difference-maker on a genuinely cold night, but it blocks considerably more light — around 30–40% — so it's not ideal for leaving on plants long-term during the growing season. I treat 30gsm as my "frost alert" fleece: it comes out when a hard frost is forecast and goes back in the shed once the danger has passed. The very heaviest 45gsm fleece, used in some ready-made tunnels, protects more again but blocks the most light, so it's strictly for the coldest snaps and tender specimens.
Pro Tip: Double Up Rather Than Going Heavy
If you've only got 17gsm fleece and a hard frost is coming, two layers of it will outperform a single layer and give you flexibility the rest of the year. You can peel one layer off once the cold passes and leave the lighter cover in place. It's cheaper and more adaptable than owning a dedicated roll of the heavy stuff.
Sizes, Tubes and Sheets
Fleece comes in flat rolls and in ready-made tubes. Flat rolls are the most versatile — a 1m x 16m roll, for instance, gives you metres of material to cut and drape however you like, and there are wider options such as 10m x 1.5m for covering broader beds. Fleece tubes are a clever variation: a 120cm x 5m tube in 30gsm slips straight over a row or a hoop frame, saving you the fiddle of clipping a flat sheet down at the edges.
Whichever format you choose, the golden rule is to leave slack. Plants grow, and fleece pulled tight will tear or restrict them. Drape generously, weigh the edges down with bricks, stones, or lengths of timber, and resist the urge to make it taut.
Fleece doesn't last forever in sunlight, even when UV-stabilised. Store it dry and out of direct sun between uses and a roll will see you through several seasons rather than shredding after one summer.
The Biodegradable Option
If the idea of accumulating yet more plastic in the garden bothers you — and it bothers plenty of us — there's now a genuinely interesting alternative in BioFleece. Rather than petroleum-derived plastic, it's made from PLA created from plant material. It performs much like conventional fleece: BioFleece 30 is a 30gsm frost fleece that will protect plants in air temperatures down to around -5°C, while the lighter BioFleece 18 protects down to about -1°C.
The catch — or the feature, depending on your viewpoint — is that it's designed to break down, starting to degrade after 12 to 18 months. It can be used year-round, though as with all fleece you'll mainly need it from October through to April. If you want frost protection without the guilt of indestructible plastic sheeting, it's well worth a look, just bear in mind you'll be replacing it more often than the conventional stuff.
Fleece Pros
- Cheapest protection per square metre by a wide margin
- Permeable to air, light and water — leave it on for days
- 17gsm lets ~80% of light through for long-term cover
- Doubles as a pest barrier against flying insects
- Folds away to almost nothing for storage
- Biodegradable BioFleece option available
Fleece Cons
- Lighter weights only buy 2–3°C — not enough for hard frosts alone
- Heavy 30gsm blocks 30–40% of light, so can't stay on long
- Tears if pulled tight or snagged on canes
- Can blow off in wind unless well weighted
- Degrades in UV over time and looks scruffy
Cloches: Individual Little Greenhouses
Cloches are the oldest trick in the book — the word comes straight from the French for "bell", because the original Victorian versions were bell-shaped glass domes plonked over individual plants. The principle hasn't changed in a century and a half: you cover a plant with a transparent cover, trap warmth and humidity, and create a snug microclimate that runs a few degrees warmer than the open garden.
Today "cloche" covers a much broader church, from those classic glass bells to lightweight plastic domes and right up to full polythene-covered row structures that are really mini polytunnels in all but name. They split roughly into two camps: small individual covers for single precious plants, and larger framed structures that protect whole beds.
Glass Bell Cloches
The hand-blown glass bell cloche is the connoisseur's choice. It gives 2–3°C of protection, which on paper matches standard fleece, but glass has a trick up its sleeve: it retains more warmth at night than thin plastic or fabric. Glass is dense and holds heat, so a glass cloche releases stored warmth back to the plant through the small hours when a fleece cover would have already given up most of its advantage. For an individual tender plant — an early courgette, a precious specimen — a glass bell is genuinely one of the most effective night-time protectors you can buy.
It's not without drawbacks. Glass is heavy, expensive, fragile, and only covers one plant at a time. Leave one on through a sunny day and you can cook the plant inside, so they demand attention — lift them on warm mornings, replace them at dusk. They're a lovely, traditional, highly effective option for the gardener with a handful of treasured plants and the time to fuss over them.
Plastic & Polythene Framed Cloches
At the other end of the scale sit the larger framed cloches, which behave more like a long, low greenhouse over a whole bed. The polythene cloches from Premier Polytunnels are a good example of how serious this category can get. They're built around a framework of 28mm diameter high-tensile galvanised steel hoops, stand 4ft wide and 3ft 7in high, and come in lengths of 6ft, 8ft, 10ft and 12ft to suit different beds.
Genuinely tough cover
The clear cover is 480 gauge / 120 micron polythene film — four times thicker and stronger than a standard cloche or dust film — and carries a 2-year warranty against UV degradation. This is a world away from the flimsy plastic that shreds in a single windy spring.
Built-in ventilation
It's supplied with two extension legs that allow quick access and ventilation, so you can crack it open on warm days without dismantling the whole thing — crucial for avoiding the cook-your-plants problem.
Rot-resistant base
Pressure-treated timber base rails anchor the structure and resist rot, so it won't rapidly rot away where it meets damp soil.
Complete kit
It arrives as a full kit ready to assemble — steel framework, timber base and polythene film all included — so there's no sourcing odd bits from the DIY shop.
What I really like about the Premier range is that the same framework comes with alternative covers for different jobs. There's a shade net version offering 40% shade and 50% wind reduction for protecting plants from scorching summer sun and drying winds, and an anti-bird net version with 20mm holes throughout to keep small animals out while preventing birds from getting tangled. Buy the structure once and you've effectively got a year-round growing aid, swapping covers as the seasons turn.
Pro Tip: Use a Framed Cloche as "Double Glazing"
If you already have a full-size polytunnel or greenhouse, a polythene cloche placed inside it acts as a second layer — effectively double glazing for your most tender plants. The trapped air between the two skins slashes overnight heat loss and can meaningfully reduce any heating costs over the coldest weeks.
Cloche Pros
- Glass bells retain warmth best of all overnight
- Framed polythene cloches use tough 120 micron film with a 2-year UV warranty
- Galvanised steel hoops won't rust
- Interchangeable covers (frost, shade, bird net) on the same frame
- Built-in ventilation legs prevent overheating
- Pressure-treated timber base resists rot
Cloche Cons
- Glass bells are heavy, fragile and cover one plant only
- Framed cloches are the priciest option to buy outright
- Any closed cloche can overheat fast on a sunny day
- Framed versions need assembly and storage space
- Less flexible than fleece for oddly shaped beds
Mini Polytunnels: The Best of Both Worlds
Mini polytunnels are, to my mind, the most practical solution for most veg gardeners who want to protect a whole row at once without faffing about. They're essentially a series of hoops — usually galvanised steel — with a cover of fleece or polythene suspended over the top, forming a tunnel you can run down a bed. The clever ones come as a single integrated unit so you're not wrestling a separate cover onto a separate frame in the wind.
Haxnicks Easy Fleece Tunnels
The Haxnicks Easy Fleece Tunnel is the design I keep coming back to recommend, precisely because it solves the most annoying part of using fleece — keeping it up off the plants and pegged down at the edges. Here the galvanised steel hoops are rust-proof and form part of the tunnel itself, so you don't have to wrestle with fitting a cover onto a frame. The cover is UV-stabilised 45gsm heavy-weight polypropylene fleece, the heaviest of the common fleece grades, which means meaningful frost protection rather than just a token layer.
The standard tunnel runs 3m long plus drawstring ends, giving you over 3m of actual growing space, in a footprint of roughly L300 x W45 x H30 cm. That's ideal for a single row of carrots, salads, brassica seedlings or early peas. For bigger plants or to cover a double row, the Giant version steps up to L300 x W60 x H45 cm — noticeably wider and taller, so it'll happily span bushier plants without crushing them against the fleece.
The thing that makes them so liveable with is storage. At the end of the season you fold them down and place them back in the original packaging, where they take up almost no room. Anyone who's tried to store a rigid frame plus a separate, awkwardly-folded sheet of fleece will appreciate how much friction that removes. The drawstring ends are the other neat touch — pull them tight to seal in warmth on a cold night, or open one end for ventilation and access on a mild day.
The Polythene Tunnel Cloche
Haxnicks also makes an Easy Poly Tunnel Cloche, which swaps the fleece for 150 micron tough UV-stabilised polythene over the same broad shape (3m x 45cm x 30cm), again with a drawstring for easy access. The choice between fleece and polythene matters more than you'd think.
Polythene traps more heat and creates a warmer, more humid greenhouse effect, which is great for getting early crops going faster — but it must be ventilated on sunny days or it'll cook the plants. Fleece is more forgiving and breathable, so it's the safer "fit and forget" choice for frost protection over several days.
Premier Polytunnels Mini Polythene Cloche
For something more robust and semi-permanent, the Premier Polytunnels mini polythene cloche brings their serious build quality to the row-cover format. It's 4ft wide and available in lengths from 6ft to 12ft, built on the same 28mm galvanised steel framework and clad in that tough 480 gauge / 120 micron polythene. It's ideal for shielding vulnerable plants from frost — whether you're using it in raised beds, out on an open plot, or as that "double glazing" trick inside a larger polytunnel to reduce heating costs. It sits at the heavier-duty end of the mini-tunnel spectrum, blurring the line between a row cloche and a small structure.
Mini Polytunnel Pros
- Covers a whole row in one go — huge time saver
- Integrated hoops mean no wrestling cover onto frame
- 45gsm fleece versions give strong frost protection
- Drawstring ends for sealing or ventilating
- Galvanised steel hoops are rust-proof
- Fold flat into original packaging for storage
- Choice of breathable fleece or warmer polythene
Mini Polytunnel Cons
- Standard size limited to ~45cm width — short plants only
- Polythene versions overheat fast if not ventilated
- Pegs/edges can lift in strong wind
- Fixed lengths suit some bed layouts better than others
- More expensive than a plain roll of fleece
Head-to-Head: Which Protects Best?
Let's put the three side by side on the metrics that matter. Remember that frost protection is measured in degrees of "lift" over the open garden, and that more protection often costs you light, money or convenience elsewhere.
| Feature | Garden Fleece | Cloches | Mini Polytunnels |
|---|---|---|---|
| Frost protection | 2–3°C (17gsm) to 4–5°C (30gsm) | 2–3°C (glass bell) | Strong with 45gsm fleece |
| Coverage | Anything you can drape | Single plant to full bed | Whole 3m+ row |
| Light through | ~80% (17gsm) | Excellent (glass/clear) | Depends on cover |
| Breathability | Permeable to air & water | Poor unless vented | Fleece good, polythene poor |
| Overheating risk | Low | High when closed | Low (fleece) / High (poly) |
| Ease of use | Very easy, just drape | Bells fiddly, frames need build | Pop-up and peg down |
| Storage | Folds tiny | Bulky / fragile | Folds into pack |
| Relative cost | Lowest | Highest (framed/glass) | Mid-range |
The Real-World Frost Test
Specs are one thing; what happens on an actual cold night is what counts. On a frosty April night I ran a simple test with a min/max thermometer, comparing the temperature under fleece against unprotected open soil. The exposed area dropped to -2.5°C, comfortably cold enough to kill tender seedlings. Under the fleece, the lowest reading was -0.5°C.
That 2°C gap doesn't sound dramatic written down, but it was the entire difference between life and death for the plants underneath. The fleece-covered bed of courgette seedlings came through unscathed, while anything exposed that night would have been lost. It's a vivid demonstration of why these humble tools punch so far above their price: frost protection isn't about creating tropical warmth, it's about nudging the temperature just over the freezing line at the critical hour.
Pro Tip: Cover Before Dusk, Not at Midnight
Fleece and cloches work by trapping warmth that's already in the soil and air. Cover your plants in the late afternoon while there's still heat to capture — not at 11pm once the cold has already set in. Putting a cover on cold plants just keeps them cold.
How to Use Them Properly
Owning the right kit is only half the battle; using it well is the other half. A few habits separate the gardeners who lose plants every spring from the ones who don't.
Time it right
Get covers on before sunset on the day a frost is forecast, and ventilate or remove them once the morning sun is up and temperatures rise above freezing. Lingering covers on a warm day risk cooking the very plants you're protecting.
Weight the edges
Most frost-protection failures are wind failures. A sheet of fleece that blows off at 2am offers nothing. Pin edges down with bricks, stones, soil or proper ground pegs so the warm air stays trapped underneath.
Leave growing room
Drape fleece loosely and choose tunnel heights that suit your crop. Where fleece touches foliage directly, that contact point can still suffer frost damage — the air gap is doing the insulating.
Keep watering
Fleece and net covers are permeable, so rain gets through — but tightly sealed polythene cloches and tunnels won't water themselves. Check soil moisture under any closed cover, especially during dry spring spells.
Ventilate polythene daily
On any sunny day, open the drawstring ends or lift the ventilation legs on polythene covers. Temperatures inside a sealed clear cover can soar within an hour of sunrise and scorch tender growth.
Ratings: How I Score Each Type
Taking everything into account — protection, convenience, cost, versatility and durability — here's how I'd rate the three categories as everyday frost-protection tools. None is perfect, and the "best" one genuinely depends on your situation, but the scores reflect how often I find myself reaching for each.
Who Should Buy What?
Rather than crowning one outright winner, here's how I'd match each tool to the kind of gardener you are. Most experienced growers end up owning at least two of these and mixing and matching through the season.
The budget starter
Buy a roll of 17gsm fleece. It's the cheapest, most flexible protection there is, doubles as a pest barrier, and will cover almost any situation you meet in your first few seasons.
The row-crop grower
A Haxnicks Easy Fleece Tunnel is made for you. Pop it over a row of carrots, salads or peas, peg it down, and forget about it. The 45gsm fleece and integrated hoops make protection effortless.
The tender-plant fusspot
A glass bell cloche over each treasured specimen gives the best overnight warmth retention of all. Just commit to lifting them on sunny mornings.
The serious plot-holder
A framed Premier Polytunnels cloche with its 120 micron film and interchangeable covers is a long-term investment that protects, shades and bird-proofs across the whole year.
The eco-conscious gardener
BioFleece made from plant-based PLA gives you frost protection down to around -5°C (the 30gsm grade) and breaks down naturally after 12–18 months. No permanent plastic in your soil.
The early-crop chaser
A polythene tunnel cloche traps the most heat for forcing early growth — just be disciplined about daily ventilation so you don't cook your head start away.
Frequently Asked Questions
It depends on how cold your nights get and how tender your plants are. Standard 17gsm fleece and glass bell cloches give 2–3°C, which handles light frosts. For harder frosts, step up to 30gsm fleece (4–5°C) or 45gsm tunnel fleece. In my real-world test, just 2°C of lift took plants from a lethal -2.5°C to a safe -0.5°C — so even modest protection often does the job.
Light 17gsm fleece lets about 80% of light through, so yes — you can leave it draped over crops for extended periods and they'll keep growing happily underneath. Heavier 30gsm fleece blocks 30–40% of the light, so it's better used as short-term overnight cover during cold snaps rather than left on through the growing season.
Fleece is breathable and forgiving — it's the safer "fit and forget" choice for frost protection over several days, with far less overheating risk. Polythene traps more heat for faster early growth but must be ventilated on sunny days or it'll scorch your plants. If you want low-maintenance frost cover, go fleece; if you're chasing the earliest possible crop and will tend it daily, go polythene.
It absolutely can. Any sealed clear cover — glass bell, polythene cloche or poly tunnel — heats up rapidly once the sun hits it. That's why good framed cloches include ventilation legs and the tunnels have drawstring ends. Open or lift them on warm mornings, and only seal them up again at dusk when frost threatens.
It varies by product. Conventional UV-stabilised fleece lasts several seasons if stored dry and out of the sun. The Premier Polytunnels polythene cloche film carries a 2-year warranty against UV degradation and sits on rust-proof galvanised steel hoops with a pressure-treated timber base. BioFleece is deliberately short-lived, beginning to break down after 12–18 months as part of its eco design.
Yes — fleece doubles as a physical barrier against flying insects like carrot fly, which is a genuine bonus of leaving lightweight fleece on through the season. Separately, the Premier Polytunnels frames can take an anti-bird net cover with 20mm holes that keeps small animals out and stops birds getting tangled, so the same structure protects against both cold and critters depending on the cover you fit.
The Verdict
My Final Take
Frost protection is one of those rare areas of gardening where spending very little money delivers a wildly outsized return. Lose a tray of seedlings to one careless cold night and you've thrown away weeks of windowsill nurturing; spend the price of a coffee on a roll of fleece and you'll never have to.
If you buy nothing else, buy a roll of 17gsm garden fleece. It's the cheapest, most versatile tool here, it buys you that crucial 2–3°C, it lets 80% of light through so it can stay on for days, and in my own test it kept a bed of courgettes alive at -0.5°C while the open soil hit a lethal -2.5°C just inches away. For row crops, a Haxnicks Easy Fleece Tunnel with its integrated rust-proof hoops and 45gsm cover takes all the faff out of protecting a whole bed and folds back into its packaging when you're done.
Step up to a framed Premier Polytunnels cloche if you want a serious, year-round structure with tough 120 micron film and interchangeable frost, shade and bird-net covers — and reach for a classic glass bell cloche when you've a precious individual plant that deserves the very best overnight warmth. Mix and match, cover before dusk, weight your edges and ventilate on sunny days, and you'll wave goodbye to those heartbreaking frosty-morning losses for good.
The headline truth is simple: you don't need to spend much, or do much, to beat the frost. A couple of degrees is all it takes — and every tool in this guide can deliver that for the price of a few seed packets. Get the basics in the shed before the clocks change, keep half an eye on the forecast, and your early sowings will reward you with weeks of head start over an unprotected plot.