How to Protect Plants from Frost
A single cold night can undo a whole season of work, but most frost damage is preventable with a little planning and a few household materials. Knowing when frost is likely and how to trap the ground's warmth around your plants lets you stretch your growing season on both ends.
Start by understanding what you are up against. A light frost settles in around 32 degrees F and mostly nips tender growth, while a hard freeze in the upper 20s or colder can kill warm-season plants outright. The riskiest nights are clear, calm, and dry, because heat that built up in the soil during the day radiates straight up into the open sky with nothing to hold it in. Cloud cover, wind, and humidity all work in your favor, so pay attention to the forecast and to your own yard: cold air is heavy and slides downhill, pooling in low spots and against fences, which is why one corner of a garden can frost while the rest is fine.
Covering plants is your most reliable tool, and it works by capturing the warmth the earth gives off overnight rather than by insulating the plant itself. For that reason the cover needs to drape all the way to the ground and be anchored at the edges with rocks, bricks, or soil, so it forms a pocket of warm air instead of a chimney. Floating row cover fabric is ideal, but old bedsheets, light blankets, or towels do the job for a night or two. Try to keep the material from crushing or pressing directly on the foliage by supporting it with stakes, tomato cages, or wire hoops, since wherever a cover touches a leaf the cold can transfer right through. Put covers on in the late afternoon or at dusk to trap the day's heat, and pull them off in the morning once temperatures climb back above freezing so plants get light and do not cook.
Water and thermal mass buy you extra degrees. Moist soil absorbs and holds far more daytime heat than dry, powdery soil, so watering your beds in the morning or midday before a frosty night gives them more warmth to release after dark. Avoid a bare sheet of plastic laid on the leaves, because plastic is a poor insulator and conducts cold to any foliage it touches; if plastic is all you have, keep it well off the plants on a frame and vent it early. You can also add heat sinks such as jugs or bottles of water set among the plants under the cover, and simple cloches like an upturned bucket or a milk jug with the bottom cut off will shelter a single seedling.
Containers deserve special handling because their roots are exposed on all sides and freeze much faster than roots in the ground. On a frost night, move pots into a garage, shed, or against a warm south-facing wall, group them together so they shelter one another, and raise them off cold concrete or pavers. For plants staying in the ground, a few inches of mulch such as straw, shredded leaves, or bark helps buffer the root zone and protect perennials and root crops. When you can, plant frost-sensitive things in your yard's warmest microclimates: gentle slopes, spots near the house or a masonry wall that soaks up sun, and away from those low frost pockets.
Timing matters as much as technique. Learn your area's average first and last frost dates as a planning anchor, then treat them as a guide rather than a guarantee, since an early or late cold snap can arrive weeks off schedule. In fall, harvest tender crops like tomatoes, peppers, basil, and squash before the first hard freeze, and let cool-season vegetables such as kale, carrots, spinach, and Brussels sprouts ride out light frosts, which often makes them noticeably sweeter. In spring, harden off indoor-grown transplants by setting them outside for gradually longer stretches over a week or so before planting, so they are not shocked by the first chilly night in the garden.
Frequently asked questions
Can I just use plastic sheeting to cover my plants?
Plastic on its own is a weak insulator, and wherever it rests against a leaf it actually conducts cold and can cause the very frost burn you are trying to prevent. Cloth covers like row cover fabric, sheets, or blankets work much better. If you only have plastic, support it on hoops or stakes so it never touches the foliage, and vent or remove it first thing in the morning before the sun heats the air trapped inside.
Does watering really help protect plants from frost?
Yes, in a useful but modest way. Damp soil stores more of the day's heat than dry soil and slowly releases it overnight, which can raise the temperature around your plants by a degree or two. Water the ground in the morning or early afternoon before a frosty night rather than late in the evening, and combine it with a cover for the best result on a cold night.
My plants got hit by frost. Should I cut off the damaged parts right away?
Wait a few days before doing anything drastic. Frosted foliage often looks worse than the actual injury, and the damaged leaves can offer a little protection to the growth beneath during the next cold night. Give the plant time to show you which stems push out new growth, then trim away the parts that are clearly dead. Many perennials and hardier vegetables bounce back once milder weather returns.
General guidance for US home gardens. Conditions vary by region and season; check with your local Cooperative Extension office for site-specific advice. Page updated Aug 4, 2026.