Frost cloth, also called horticultural fleece, is a lightweight fabric draped over plants to protect them from frost. It is the simplest and cheapest form of frost protection: a sheet of cloth, a few bricks to hold it down, and a plant that would otherwise be damaged by a cold night can survive until morning. It is used to protect early sowings, young transplants, tender plants and blossom from late spring frosts, and to extend the season for salads and herbs in autumn. This guide covers how frost cloth works, how to fit it, and when to use and remove it.
Frost cloth works by trapping a small amount of warmth around the plant and by keeping frost off the leaves. On a clear, still night, heat radiates away from the ground and the plant, and frost forms on exposed surfaces. A layer of frost cloth slows that loss of heat, and frost forms on the cloth instead of on the leaves. It does not heat the plant — it only softens the cold — so it protects against light frosts, not against hard, prolonged freezes. For a hard frost, a tender plant needs more protection: a cold frame, a cloche, or being brought indoors. Use the frost date calculator to check your local frost dates, and our winter frost protection guide for the full range of frost protection methods.
Fitting frost cloth
Drape the cloth loosely over the plant, leaving enough slack for the plant to grow and for air to circulate, and fix the edges firmly with bricks, stones, soil or pegs so wind cannot lift it and cold air cannot blow in underneath. For a single plant, a double layer gives more protection than a single layer, but it also lets in less light, so do not leave a double layer on during the day. For a row of plants, support the cloth on hoops or canes so it does not lie heavily on the leaves: fabric that touches the leaves can itself freeze and damage them, and the weight can crush young seedlings. Our row covers guide covers hoops and row protection in detail.
Put frost cloth on in the late afternoon, before the temperature falls, and take it off in the morning once the frost has lifted and the sun is up. Do not leave it on during a sunny day, because it can overheat the plant underneath and it cuts the light. Do not leave it on for days at a time in damp weather, because the damp, still air underneath encourages mould and slugs. Check the plant when you remove the cloth, and remove any dead or damaged leaves promptly.
What frost cloth protects
Frost cloth protects against light frosts, which are the most common frosts in spring and autumn. It is ideal for young transplants such as tomatoes, courgettes, peppers and beans planted out in late spring, when a single late frost could kill them — see growing tomatoes and growing peas. It protects early sowings of lettuce, radishes, peas and potatoes, and it protects the blossom of fruit trees and bushes from a late frost that could wipe out a whole year's fruit. It also protects salads and herbs in autumn, extending the harvest by weeks after the first frosts. For tender plants in pots, move the pots to a sheltered spot against a warm wall and cover them with frost cloth, or bring them indoors on the coldest nights. If you are unsure what will survive a frost in your area, check your local extension service for advice.
Choosing and caring for frost cloth
Frost cloth is sold in rolls and pre-cut lengths, in different weights. A light cloth is easy to handle and suits a single light frost; a heavier cloth gives more protection but lets in less light and is heavier to handle. For most home gardeners, a medium-weight cloth is the most useful, and a double layer can be used on the coldest nights. Do not use plastic sheeting as frost cloth: plastic does not breathe, it traps damp air, and where it touches the leaves it can freeze and damage them. Use a proper horticultural fleece, which lets air and water through while holding in warmth.
Look after frost cloth and it will last several seasons. Remove it carefully, shake off soil, let it dry fully before folding it away, and store it dry and out of direct sun, because sunlight degrades the fabric. Repair small tears with tape or stitching, and replace a cloth when it becomes thin, torn or brittle. Keep a length of frost cloth handy through spring and autumn, because a frost is often forecast only a day or two ahead, and a cloth that is ready to use is far more useful than one buried in the back of a shed.
Frost cloth and other protection
Frost cloth works best as part of a set of methods, not on its own. A plant in a sheltered spot against a warm wall, with frost cloth over it, is far better protected than the same plant in an exposed spot with a cloth. Watering the soil before a frost is forecast can help, because moist soil holds more heat than dry soil — but do not water the leaves, and do not water in freezing weather. Mulching the soil around a plant insulates its roots, and a cloche or a cold frame gives more protection than a cloth alone. For the coldest nights, combine methods: a cloche covered with frost cloth, or a plant in a cold frame with frost cloth over the lid, gives far more protection than any single method. If a plant is badly damaged by frost, do not cut it back immediately: wait until the weather warms up and new growth appears, so you can see what is alive and what is dead.
Common mistakes
The most common frost cloth mistakes are putting it on too late, after the frost has already formed; leaving it on during a sunny day so the plant overheats; letting the cloth touch the leaves, where it can freeze and damage them; using plastic sheeting instead of proper fleece; and expecting it to protect a tender plant from a hard freeze. Another is forgetting to check under the cloth for slugs, which love the damp shelter. The fixes are simple: put the cloth on before the temperature falls, take it off in the morning, support it on hoops or canes, use proper horticultural fleece, and bring tender plants indoors on the coldest nights.
Frequently asked questions
What is the difference between frost cloth and row covers?
Frost cloth is the material — a lightweight horticultural fleece — while a row cover is a way of using it: a length of fleece or mesh fitted over a row of plants, usually on hoops. Frost cloth can be used as a row cover, or draped over a single plant, or laid over a cloche or cold frame for extra protection on a very cold night.
Can I leave frost cloth on all winter?
No. Frost cloth should be put on before a frost and taken off in the morning once the frost has lifted. Leaving it on for days cuts the light, traps damp air, and encourages mould and slugs. For winter-long protection, a cold frame or a greenhouse is a better tool.
Will frost cloth protect tomatoes from frost?
It protects young tomato plants from a light frost, which is often enough in late spring when the frost is mild and short. It will not protect them from a hard, prolonged freeze. If a hard frost is forecast, bring potted tomatoes indoors or add a cloche and a second layer of cloth, and plant tomatoes out only after the last frost date in your area.
Can I use a bed sheet or blanket instead of frost cloth?
An old sheet or blanket can work for one night in an emergency, because it also traps warmth and keeps frost off the leaves. But it is heavier than frost cloth, it can crush young plants, it holds water and becomes very heavy when wet, and it lets in less light if left on during the day. Proper horticultural fleece is lighter, lets air and water through, and is the better long-term choice.
How do I know when a frost is coming?
Check the weather forecast for your area, and watch for the signs: a clear, still evening after a cold day, with a falling temperature, often means a frost overnight. The frost date calculator gives your local average first and last frost dates, but a forecast is the best guide to a frost on a particular night.