Frost Cloth for Plants: How to Use It and When

Updated September 2026 · Garden Advice Guide

Frost cloth for plants is a spun-bonded polypropylene or polyester fabric that traps the heat leaking out of the soil at night, and that trapped heat is what keeps the leaves under it a few degrees warmer than the open air. A lightweight cloth (about 0.5 ounces per square yard) buys you roughly 2 to 4 degrees, a medium weight (around 1 ounce) buys 4 to 6, and a heavy frost blanket (1.5 to 2 ounces) buys 6 to 8, sometimes a little more. It only works if the edges touch the ground, it goes on in the late afternoon while the soil is still warm, and it comes off the next morning once the air climbs above freezing.

That's the whole method. Everything below is the detail that decides whether your tomatoes are still alive the morning after.

Start with your date: find your average first fall frost with our free frost date lookup so you know which week the cloth needs to be staged by the back door instead of buried in the garage.

Updated September 2026

How frost cloth for plants actually works

On a clear, calm night the ground radiates its stored heat straight up into the sky. Leaves, mulch, and the tops of plants cool faster than the air around them, which is why you can get frost on the lettuce when the thermometer on the porch never dropped below 35°F. The leaf surface itself was colder than the air.

Frost cloth is a lid, not a heater. During the day the sun warms the top foot or so of soil. After sunset that soil gives its heat back, and a fabric tent catches it and holds a pocket of slightly warmer, slightly more humid air around the plants. The fabric also stops frost from forming directly on leaves, because the cloth takes the cold instead.

Three things follow from that, and they explain most frost cloth failures:

• The cloth must reach the ground on every side. A gap lets the warm air out and the cold air in, and you've built a tent that does nothing.
• The soil is the heat source, so don't insulate it away from the plants. A deep layer of dry straw or bark under the cloth blocks the warmth from rising. On frost nights, bare or thinly mulched soil under a cover holds plants warmer than a deeply mulched bed.
• Moist soil holds more heat than dry soil. Watering the bed that morning gives the cloth more warmth to trap that night.

Plastic sheeting works on the same principle but fails in two ways. Where it touches a leaf it conducts the cold straight through, so every contact point frosts. And on a sunny morning it turns the bed into a steam room within an hour. If plastic is all you have, tent it well clear of the foliage and pull it at sunrise.

Frost cloth weights and the degrees of protection each gives

Frost cloth is sold by weight, measured in ounces per square yard. That number is on the label, and it's the only spec that tells you what the fabric will do. Ignore the marketing words and read the weight.

Those protection figures are what manufacturers rate their fabric for, and they assume a sealed edge and a calm night. Wind steals warmth from under any cover, so on a breezy night knock 2 degrees off whatever the label promises. The National Weather Service glossary is the place to check what your local forecast means by frost versus freeze, because the difference decides which weight you reach for.

Here's what those ratings mean on an actual night, using tomatoes as the example because they're the plant most people are trying to save. Tomato foliage is damaged at 32°F and the fruit is ruined a degree or two below that.

That last row is worth saying plainly. No cloth saves tender plants from a real hard freeze. Below about 25°F you pick everything you can and let the rest go, and you spend the cloth on the semi-hardy crops that only need a few degrees to stay in good condition.

Draping to the ground vs tenting over hoops

There are two ways to put frost cloth on, and the plant decides which.

Draping means laying the fabric directly over the plants and pinning the edges. It's fast, it works, and for tough plants it's all you need. Lettuce, spinach, kale, chard, beets, broccoli, pansies, and low-growing herbs are fine with cloth resting on them. Use it for a night or two on anything.

The catch is contact. Wherever fabric touches a leaf, that leaf sits at fabric temperature rather than at tent temperature, so on a cold night the contact points frost even though the rest of the plant is fine. On kale that's a cosmetic nick. On basil, peppers, impatiens, or a tomato full of fruit, those contact burns are the damage you were trying to avoid. Rain and heavy dew also soak the fabric and flatten it onto the plants, which makes the contact problem worse.

Tenting means holding the cloth above the plants on a frame so it touches nothing. This is how you protect anything tender, anything tall, and anything you want to keep covered for several days.

The frame can be:

• Half-inch PVC pipe bent into arches and slipped over 12-inch rebar stakes pushed into the bed edges. Space arches 3 to 4 feet apart.
• 9-gauge wire cut to about 6 feet and bent into hoops for low crops. Cheap, quick, and it stores flat.
• Tomato cages or stakes already in the bed. Throw the cloth over the top and let the cages hold it up.
• A frame of stakes around a shrub so the cloth hangs like a tent, not a wrap.

Whatever the frame, leave at least 6 inches of air between the fabric and the tallest leaf, and make the tent wide enough that the cloth still reaches the ground on both sides after it drapes over the arch.

The one shape that fails is the wrapped lollipop: cloth gathered and tied around the trunk of a shrub or small tree with the ground left open. That wrap excludes the soil's heat entirely, so the plant inside ends up almost as cold as the open air. Frost cloth over a shrub has to go all the way to the ground, and a couple of bricks on the skirt are what make it work.

Covering a bed, step by step

1. Water the bed in the morning if the soil is dry. Moist soil stores more daytime heat.
2. Set hoops or stakes in the afternoon so you're not doing it in the dark. Check the tallest plant clears the frame by 6 inches.
3. Cut or unfold enough cloth to cover the frame and leave 12 to 18 inches lying flat on the ground on every side.
4. About an hour before sunset, pull the cloth over. The soil is still warm and the air hasn't started to drop.
5. Seal the entire edge with bricks, boards, sandbags, rocks, or landscape staples every 2 feet. Then walk the whole perimeter once more. One open corner is enough to fail.
6. On a windy night, add a rope or a second row of weights over the top so the cloth can't lift.
7. The next morning, once the air is above freezing and any frost on the outside of the cloth has melted, fold it back or remove it.

When to put frost cloth on and when to take it off

Put it on in the late afternoon, ideally an hour before sunset. The soil is at its warmest and the cloth gets the whole evening's heat release. Covering at 10 p.m. after you notice the temperature falling still helps, but you've already lost the first few hours of stored warmth.

Cover on any night the forecast low is 36°F or below and the sky is clear and the wind is calm. Frost forms on plant surfaces at air temperatures a few degrees above 32°F on nights like that, which is exactly why the National Weather Service issues frost advisories in the 33 to 36°F range. A cloudy or windy night at 34°F usually doesn't frost. A crystal-clear, dead-still night at 35°F often does. If the dew point in the forecast is far below the expected low, the temperature tends to fall further than predicted.

Take it off in mid-morning, once the air has climbed above freezing. The coldest moment of the night is right around sunrise, not midnight, so peeling the cloth back at first light is the worst possible timing. Wait until the frost on the grass has melted.

How long a cloth can stay on depends on its weight:

• Lightweight passes so much light that fall greens can live under it for weeks. Many gardeners leave it on a bed of lettuce and spinach from the first frost until Thanksgiving.
• Medium is fine for a stretch of cold days, three or four at a time. Lift it on any sunny afternoon to vent.
• Heavy blocks half the light or more and traps heat on a sunny day. Off in the morning, back on at dusk, every time.

When the first frost usually arrives, by zone

These are the average first fall frost dates behind our frost date lookup, rounded to the week. Have the cloth cut, labeled, and staged two weeks before your date, because roughly half of all years frost earlier than the average.

The tool gives you the date for your ZIP code, which matters more than the zone average. Zone is built from winter lows, not frost timing, and two towns in the same zone can be three weeks apart on first frost.

Which plants are worth covering, and which aren't

Covering is a triage decision. Some plants gain weeks of harvest from a single night under cloth. Others won't notice the frost at all, and a few can't be saved by any fabric.

Cover at 32°F, or harvest instead: tomatoes, peppers, eggplant, basil, cucumbers, summer squash, beans, sweet potato vine, coleus, impatiens, begonias, celosia, dahlias in bloom. A first frost is usually followed by two to four weeks of mild weather, so one or two covered nights can carry these to a second harvest. That's the highest-value use of frost cloth all year.

Cover at 28°F to keep quality: lettuce, chard, beets, carrots, celery, cauliflower, peas, cilantro, parsley, pansies and violas in bloom, snapdragons. These survive a light frost uncovered but come through it cleaner and keep producing longer under cloth.

Don't bother until the low 20s: kale, collards, spinach, Brussels sprouts, leeks, parsnips, cabbage, ornamental kale. Frost improves them. Lightweight cloth over a bed of these in late fall is about extending the picking window in a cold zone, not about saving them.

Never in fall: hardy perennials, established shrubs, and trees. Their tops are meant to die back or go dormant. Frost cloth on those is a spring tool, for protecting new growth, blossoms, and fruit set during a late cold snap.

The full ranked method set, including watering, mulching, and what to do with pots, is on our sister page on how to protect plants from frost. This page stays on the cloth itself.

Spring: the other half of the year

The same cloth earns its keep again in April and May. Transplants going out one to two weeks after your average last frost (that's the window our frost date tool calculates) still hit the occasional 30°F night, and medium cloth over hoops is what lets you plant on schedule instead of waiting until June. Lightweight cloth also softens sun and wind for seedlings coming out of the house, which is why it shows up in our hardening off seedlings schedule.

Strawberries are the classic spring case. Open blossoms are killed at 30°F, and they open weeks before the last frost in most zones, so a length of cloth stays folded at the end of the bed from first bloom until the frost date passes. The timing is in when to cover strawberries.

Reusing and storing frost cloth

Spun-bonded fabric lasts several seasons if you treat it well and one season if you don't. The two things that kill it are sunlight and being stored wet.

• Dry it completely before it goes away. Hang it over a fence or a clothesline for a full sunny day. Damp cloth stored in a bin mildews, and mildewed fabric tears.
• Fold it, don't stuff it. Folding along the same lines each time keeps it flat and easy to unroll in the dark. Crumpled cloth develops weak creases.
• Store it in the dark. Ultraviolet light degrades polypropylene. A cloth left on a bed all summer as shade goes brittle by fall. A cloth kept in a lidded bin in the garage is good for years.
• Keep mice out. A bin with a lid, not an open bag. Rodents love the stuff for nesting.
• Label each piece by weight and size. A strip of tape reading "medium, 10 by 12, tomato bed" saves you from unfolding four pieces at dusk to find the right one.
• Patch small tears with tape or a few stitches. Replace a piece once it tears at a light pull, because it will split the first windy night.

Cut new cloth to fit your beds the first time you use it, with the extra 12 to 18 inches on each side already accounted for, and write the bed name on it. From then on covering a bed takes two minutes.

Off season, lightweight cloth doubles as insect netting over brassicas and squash and as shade cloth for lettuce in July. Medium and heavy pieces should stay in the bin until they're needed.

Common frost cloth mistakes

• Leaving a gap at the bottom. The single most common reason "the cloth didn't work."
• Wrapping and tying instead of tenting to the ground. Excludes the soil heat.
• Covering at bedtime instead of before sunset. Loses the evening's warmth.
• Uncovering at dawn. The coldest minutes of the night are at sunrise.
• Leaving heavy cloth on through a sunny day. Overheats and starves plants of light.
• Mulching deeply under the cover on frost nights. Insulates the heat away from the plants.
• Trusting the label rating on a windy night. Subtract 2 degrees.
• Expecting cloth to save tomatoes at 22°F. Harvest instead.

Worked example: a zone 6b raised bed on October 19

Say you're in zone 6b, where our tool puts the average first frost around October 20. The forecast for tonight is 30°F, clear, wind under 5 mph, dew point 24°F. That combination means the real low could land a degree or two under the forecast.

The bed is 4 by 8 feet. In it are three tomato plants at 4 feet tall on cages, two pepper plants, a clump of basil, and a row of lettuce along the front.

The decision: tomatoes, peppers, and basil are damaged at 32°F. Medium cloth (4 to 6°F) puts them at 34 to 36°F under the cover, which is safe with a small margin. Because the dew point suggests the forecast may run warm, you double a second medium piece over the tomato end and the peppers, which adds another 2 to 3 degrees. The lettuce doesn't need anything at 30°F but it's under the same cloth anyway.

The cloth size: the cages hold the fabric up at about 4 feet. A 4-foot-wide bed with a 4-foot-tall frame needs roughly 4 feet up, 4 feet across, and 4 feet down, plus 18 inches on the ground each side. Call it 15 feet wide. Length is 8 feet plus 2 feet each end, so 12 feet. A 15 by 12 piece covers it.

The timing: you water the bed at 9 a.m. At 5:30 p.m., about an hour before sunset, you pull the cloth over the cages and pin every edge with bricks and two boards. The doubled section goes over the tomatoes. You check the perimeter once more with a flashlight at 8 p.m.

The morning: the porch thermometer bottomed at 29°F at 6:45 a.m. At 9:30 a.m. the frost on the lawn is gone and the air reads 38°F. You fold the cloth back. The tomato leaves are green, the peppers are fine, and the basil is untouched. The next ten days run in the 50s and 60s, and you pick another two dozen ripe tomatoes before the next frost on November 1, when the forecast says 24°F and you harvest everything green and pull the plants.

Two covered nights, three extra weeks of tomatoes. That's what frost cloth is for.

Frequently asked questions

Can I leave frost cloth on plants all day?

Lightweight cloth, yes, for weeks at a time, because it passes most of the light and breathes well. Medium cloth is fine for a few cloudy days but should be vented on sunny afternoons. Heavy frost blankets block half the light or more and trap heat, so they come off every morning and go back on at dusk.

Does frost cloth work without hoops?

Yes, for hardy and semi-hardy plants such as lettuce, kale, chard, beets, and pansies. Lay it directly on them and pin the edges to the ground. For tender plants like tomatoes, peppers, basil, and impatiens, hoops or cages matter, because any leaf touching the fabric frosts at the contact point even when the rest of the plant is fine.

How much warmer is it under frost cloth?

It depends on the weight. Lightweight cloth (about 0.5 ounces per square yard) holds plants 2 to 4°F warmer than the open air, medium (around 1 ounce) holds 4 to 6°F, and heavy frost blankets (1.5 to 2 ounces) hold 6 to 8°F. Those figures assume the edges are sealed to the ground and the night is calm. Wind cuts them by about 2 degrees.

Can I use a bed sheet or a tarp instead of frost cloth?

An old cotton sheet works about as well as lightweight cloth for a single night, so it's a fine emergency cover for a 33°F forecast. It soaks through with dew and gets heavy, and it gives almost nothing once wet. Plastic tarps protect only if tented clear of the leaves and pulled at sunrise, because plastic conducts cold at every contact point and cooks plants in morning sun.

Should I water plants before covering them with frost cloth?

Yes, in the morning of the frost day, if the soil is dry. Moist soil absorbs more daytime heat and releases it more slowly overnight, which gives the cloth more warmth to trap. Don't water in the evening, and don't wet the foliage, since wet leaves under a cover frost more easily.

Will frost cloth protect plants from a hard freeze?

Only partly. A heavy blanket over hoops adds 6 to 8°F, so at a hard freeze of 28°F tender plants under it sit at about 34 to 36°F and survive. At 24°F they sit at about 30 to 32°F and are marginal, and at 20°F they're lost. When the forecast drops into the low 20s, harvest tender crops that afternoon and spend the cloth on the semi-hardy ones.

How many seasons does frost cloth last?

Several, if it's stored dry, folded, and out of sunlight, and the same piece can serve spring and fall each year. Ultraviolet light is what breaks the fibers down, so cloth left on a bed through summer often goes brittle by fall. Patch small tears and retire a piece once it rips at a light pull.