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17gsm vs 30gsm horticultural fleece

Updated: 22 October 2026

A clear night is forecast just below freezing, and two fleece rolls are in the basket. One title says 17 gsm, another says 30 gsm, and a light listing still prints −5°C or −6°C. The question is which weight matches that forecast, and which temperature line is a guide rather than a sales bullet. The RHS and Gardeners' World set the margin. Sheets and prices are on the [Frost protection fleece](/hub/garden-supplies/frost-protection-fleece) comparison. Peter F. checked the listings on 19 October 2026, with no lab trial. A qualifying purchase can earn a commission at no extra cost to you.

A clear night is forecast just below freezing, and two fleece rolls are in the basket. One title says 17 gsm, another says 30 gsm, and a light listing still prints −5°C or −6°C.

Our top picks

Ambassador Ambassador 17 g/m² fleece, 20 m × 1 m

Best overall

Ambassador Ambassador 17 g/m² fleece, 20 m × 1 m
8.3/10about £5.86
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OAHAO OAHAO 40 gsm fleece, 2 m × 5 m

Rank 2

OAHAO OAHAO 40 gsm fleece, 2 m × 5 m
8.3/10about £9.38
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CHEOAR CHEOAR 30 gsm fleece, 9 m × 3 m

Rank 3

CHEOAR CHEOAR 30 gsm fleece, 9 m × 3 m
1.6/10about £15.99
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On this page
  1. 1.What the two grades are for
  2. 2.Why the Celsius figures do not match
  3. 3.Which sheets in this set sit in each grade
  4. 4.When a second layer is the tactic

What the two grades are for

17 gsm fleece is the light cover when the air only just crosses freezing. About 30 gsm is the heavier grade titles often call heavy duty horticultural fleece. The RHS describes heavier grades as giving about 2°C and sets 17 g beside cloth of about 35 g. Gardeners' World puts 17 g just below freezing and 30 g around −3°C. Ambassador, at £5.86 for 20 m × 1 m, will cover a narrow salad row for a touch of frost if you lift it after breakfast. The same cloth through nights near −4°C sits outside those guides. Heavier fleece also cuts more light. Choose 17 gsm for a slight frost you will uncover, and about 30 gsm for one layer in the −3°C band.

Why the Celsius figures do not match

Gardeners' World keeps 30 g around −3°C and 17 g just below freezing. Quickcrop calls about −3°C realistic for 25–30 gsm and says not to rely on −6°C. Harrod Horticultural quotes −2°C to −3°C for 30 g fleece. Garden Focused puts 17 g near −2°C and 30 g near −5°C, and says wind can void the result. Andermatt Garden puts 30 gsm at −5°C to −6°C, closer to amazon.co.uk bullets than to Gardeners' World, so that line on these listings is a seller's claim. P. Wolf at £20 pairs a −5°C or −6°C bullet with a UK review that calls the cloth thin. Halatool at £18.29 prints those same degrees on a 3 m × 10 m title. Jackets around 70 g are a separate line, on plant fleece jackets.
Ambassador Ambassador 17 g/m² fleece, 20 m × 1 m

Testsieger

Ambassador Ambassador 17 g/m² fleece, 20 m × 1 m
8.3/10about £5.86
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Which sheets in this set sit in each grade

Ambassador, GardenGloss and P. Wolf are the 17–18 g sheets: £5.86 for 20 m × 1 m, £7.99 for 1.5 m × 10 m, and £20 for a titled 2 m × 20 m that a reviewer called thin. CHEOAR is about 30 gsm at £15.99 for 9 m × 3 m, with no reviews, so the size is unchecked. Halatool's 3 m × 10 m title clashes with reviews on the size that arrived. Lepat is £7.79 for 2 m × 5 m, with 35 gsm in the title and 30 gsm in a bullet. OAHAO is 40 gsm at £9.38 for 2 m × 5 m. Its 24°F bullet is about −4°C and remains a seller's figure. It does not make 40 gsm twice as warm as 17 g. Width and that clash are on the frost protection fleece buying guide.

When a second layer is the tactic

The RHS recommends a second layer on the coldest nights. Folding a 17 g sheet, as Garden Focused describes, roughly doubles the layer. It does not turn 17 gsm into 30 gsm, and a shop's −5°C claim does not come with the fold. Light transmission falls as you add a skin. One cold night of double fleece over winter lettuce is a fair exchange. A mild week under two layers will blanch the leaves. Pegging and storing that cover is on how to use garden fleece. For a typical UK frost, keep 17 gsm and double it only on the coldest night. Buy about 30 gsm when you want one heavier sheet.

Common questions

How many degrees does 17 gsm fleece add?
Gardeners' World puts 17 g fleece just below freezing, a short step under 0°C. The RHS gives heavier grades about 2°C of protection and sets 17 g beside cloth of about 35 g. Garden Focused and Andermatt Garden go towards about −1°C or −2°C. On a UK bed, use the just-below-freezing line, and treat a colder figure on a 17 g packet as a seller's claim.
Is 30 gsm enough for a typical UK frost?
A typical British frost only just falls below freezing, and 17 gsm already matches that if you can take the sheet off. 30 gsm is the heavier step. Gardeners' World puts 30 g around −3°C, Quickcrop calls about −3°C realistic for 25–30 gsm, and Harrod quotes −2°C to −3°C. That covers many inland nights. Quickcrop still warns you off −6°C, especially in wind.
What does a −6°C claim mean?
A −5°C or −6°C line on these amazon.co.uk listings is the seller's bullet. The RHS and Gardeners' World use a milder margin. Andermatt Garden prints −5°C to −6°C for 30 gsm, which is why those numbers show up on product pages. Quickcrop keeps 25–30 gsm near −3°C. P. Wolf pairs a −5°C or −6°C bullet with a UK review that calls the cloth thin.
Does folding 17 g fleece make it 30 g?
Folding leaves the cloth at 17 gsm. Garden Focused calls a folded 17 g sheet roughly double the layer, and the RHS suggests a second layer on the coldest nights. You get two thicknesses of light fleece, less light on the leaves, and a fold the wind can open. Choose the heavier roll when you want 30 gsm in one piece.
Which listings in this set are 17 or 18 gsm?
Ambassador, GardenGloss and P. Wolf are the 17–18 g sheets. Ambassador is £5.86 for 20 m × 1 m, GardenGloss is £7.99 for 1.5 m × 10 m, and P. Wolf is £20 for a titled 2 m × 20 m. CHEOAR and Halatool sit nearer 30 gsm. Lepat at £7.79 mixes 35 gsm in the title with 30 gsm in a bullet. OAHAO is 40 gsm at £9.38. These listing prices will move.
Will 17 g cloth survive a second winter?
The RHS says 17 g polypropylene can break down within a year, so a second season is uncertain. Sun, wind and pegging shorten it, and a split along a row lets frost through. Heavier cloth often lasts longer in ordinary use, though this set was not aged in a trial. If the fleece is chalky and torn by spring, replace it before the next frost.

Related pages

Best frost protection fleece

Frost protection fleece

Garden fleece buying guide: gsm, width, sheet or jacket

How to use garden fleece before the temperature falls

Plant fleece jacket size, drawstring and waterproof

Sources

Public UK sources for this comparison. Prices, stars and review counts are the amazon.co.uk listings in this set, captured 19 October 2026. Page updated 22 October 2026.

  1. RHS: fleece and crop covers (retrieved 22 October 2026)
  2. RHS: frost damage (retrieved 22 October 2026)
  3. RHS: fruit frost protection (retrieved 22 October 2026)
  4. Met Office: frost and ice (retrieved 22 October 2026)
  5. BBC Gardeners' World: garden fleece (retrieved 22 October 2026)
  6. Quickcrop: types of frost protection (retrieved 22 October 2026)
  7. Harrod Horticultural: 30 gsm garden fleece (retrieved 22 October 2026)