Garden Fleece: Which Grade and How to Use It

Garden fleece is a thin, white spun fabric you lay over plants to keep off frost, wind and pests. It lets light, air and rain through, so crops can stay under it for weeks. Pick the right grade, fix it down well and know when to lift it, and it will save a lot of plants.

This guide covers fleece itself: grades, which crops to cover, how to pin it down and when to take it off. For other ways to beat the cold, such as mulching, moving pots and wrapping shrubs, see the wider guide on protecting plants from frost.

What do the fleece grades mean?

The grade is the weight of the fabric in grams per square metre. Heavier fleece traps more still air, so it keeps plants warmer. It also blocks more light, which slows growth underneath.

17g fleece is the spring all-rounder. Crops can grow under it for weeks, which is why it doubles as an insect barrier. 30g fleece is the winter grade. Growth slows under it, but overwintering crops are hardly growing anyway. Heavy fleece is an emergency blanket for a cold night or two, not a growing cover.

If you only buy one roll, make it 17g. You can always double it up on a hard night.

Side by side, the lighter 17g fleece is clearly thinner and more see-through than the 30g winter grade.

How much frost does fleece keep off?

A single layer of 17g fleece keeps plants about 2°C warmer than open ground on a frosty night. 30g fleece manages about 3-4°C. That is enough to see most hardy and half-hardy crops through a light to moderate frost.

Fleece works by holding in the warmth the soil gives off overnight. It works a bit like cloud cover, which is why the hardest frosts come on clear, still nights. It won’t save frost-tender plants such as tomatoes or courgettes in a hard frost, so keep those indoors until late May or early June.

A thermometer tucked under the cover shows you how much warmer the soil stays than the frosty bed next to it.

When should fleece go on and come off?

Fleece is most useful from September to late May. In a cold inland garden, the last spring frost can land in late May and the first autumn frost by mid-September. Mild coastal and city gardens can shift everything a few weeks.

Fleece on at dusk when frost is forecast and off again mid-morning: a two-minute job that saves a lot of plants.

The most useful habit is a quick look at the evening forecast from early September. Fleece on at dusk and off by mid-morning takes a couple of minutes.

How to stop fleece blowing away

Wind is the main reason fleece fails. Fix the edges every 50cm all the way round, and use one of these methods.

1. Fleece pegs. Push plastic U-shaped pegs through the fabric into the soil every 50cm. Quick and reusable, and fine for sheltered beds.
2. Bricks or stones. Sit them on a fold of fabric, not a single tight layer, or gusts tear it around the weight.
3. Burying the edges. Dig a shallow trench about 10cm deep along the windward side, lay the edge in and backfill. Wind has nothing to get under.
4. Hoops. Bend lengths of plastic water pipe over the bed to make a low tunnel, then peg the fleece over it. Hoops keep the fabric off soft leaves.

Leave a little slack over growing crops. Fleece pulled drum-tight holds plants back as they push against it, and it tears sooner in wind. In exposed gardens, combine pegs with a buried windward edge.

Pegs every 50cm, plus a brick on a fold of fabric, keep the cover in place on a windy plot.

Which crops need fleece, and which grade?

Early carrots, young brassicas, strawberries and winter salads gain the most from fleece. Fully hardy crops such as garlic, parsnips and leeks don’t need it at all.

Fleece as a pest barrier is often overlooked. A carrot bed kept covered from sowing day keeps the flies off, and the guide to stopping carrot root fly covers the details. The same cover protects young brassicas and salads from flea beetle holes in their first weeks. For finer mesh over brassicas all summer, insect netting lasts longer than fleece.

The big exception is crops in flower. Strawberries, broad beans and fruit blossom need insects to set fruit, so lift the fleece by mid-morning once the frost has cleared. The guide to growing strawberries covers the early-crop routine in full.

Hoops hold the fabric clear of soft leaves, which helps stop frost scorching them through the cover.

Fleece, cloche or cold frame?

Fleece is the cheapest way to cover a lot of ground, and it fits any bed shape. Rigid covers do some jobs better.

Fleece, cloche and cold frame side by side: fleece covers the most ground, while rigid covers hold more daytime warmth.

Glass and plastic covers trap much more daytime warmth, which helps early sowings get going. The guide to cloches and low tunnels shows where that extra heat pays off. For raising young plants and getting them used to outdoor life, a frame beats fabric. The guide to cold frame gardening covers how to use one. Many gardeners use fleece inside a cold frame or greenhouse on the coldest nights for an extra layer.

Common garden fleece mistakes

• Fleece resting on leaves on a frosty night. Leaves pressed against frozen fabric can scorch through it. Use hoops over soft growth, or leave some slack.
• Weighting only the corners. Wind gets under any loose edge. Fix it every 50cm and bury the windward side.
• Leaving flowering crops covered all day. No insects means little or no fruit. Lift the fleece by mid-morning.
• Using heavy fleece for weeks. It blocks too much light, and crops turn pale and leggy. Save it for short cold snaps.
• Storing fleece damp. It goes mouldy and tears along the folds. Dry it on the washing line first, then store it in the shed.

Frequently asked questions

What is the difference between 17g and 30g garden fleece?

17g fleece gives about 2°C of frost protection; 30g gives about 3-4°C. The number is the weight of the fabric per square metre. The lighter grade lets through more light, so crops can grow under it for weeks. The heavier grade suits hard frosts and winter cover. Two layers of 17g work much like one layer of 30g.

Can plants stay covered with fleece all the time?

Hardy crops can, but plants in flower need uncovering for pollination. Carrots under fleece as a pest barrier can stay covered from sowing to harvest. Strawberries, broad beans and fruit blossom need to be open to insects by mid-morning. Put the fleece back at dusk if another cold night is forecast.

Does garden fleece let rain through?

Yes, rain and watering pass straight through the fabric. You can water through it without lifting it. Heavy rain can weigh slack fleece down onto seedlings, so hoops help over soft growth. Air passes through too, so crops don’t overheat on a mild day.

When should fleece go on in autumn?

Cover tender crops before the first forecast frost, often from mid-September. Frost hollows and cold inland gardens get frost earlier than towns nearby. Check the overnight forecast each evening from early September. Fleece on at dusk and off by mid-morning takes a couple of minutes.

How long does garden fleece last?

Fleece usually lasts a few seasons if dried before storing. Fleece folded away damp goes mouldy and tears along the creases. Sunlight weakens the fibres, so keep spare rolls in a shed rather than outdoors.

Is fleece better than a cloche or cold frame?

Fleece is cheaper and covers more ground; rigid covers hold more warmth. Fleece drapes over any bed shape and folds away flat. Cloches and cold frames trap more daytime heat, so each is useful for different jobs.

Now your crops are snug under fleece, read the guide on overwintering plants for the rest of the winter jobs, or browse more how-to guides.