How to Protect Plants from a Late Spring Frost

Know what you are protecting

Start by sorting your plants by how much cold they can take:

Tender plants such as tomatoes, peppers, basil, beans, squash, cucumbers and melons are damaged by frost. These need protecting first.
Half-hardy plants such as lettuce, chard and potatoes usually handle a light frost but appreciate cover in a hard one. Emerged potato leaves can be nipped but the plant usually regrows from below ground.
Hardy crops such as kale, cabbage, broccoli, spinach and peas generally ride out a light frost once they are hardened off. Very young transplants, or a hard freeze into the low 20s °F, can still damage them.

Our cool- vs. warm-season crop guide has the full list.

Two kinds of cold night

Radiation frost happens on clear, calm nights. Heat radiates from the ground and plants into the open sky, and leaves can get colder than the air measured at head height. That is why frost can form on plants when the official low is a few degrees above 32°F. Covers work well against radiation frost, because they trap the heat the soil gives off.
Freezes from cold air moving in come with wind and a large mass of cold air. Covers help less here, because wind strips heat away and the whole air mass is cold. If a hard freeze with wind is forecast, move containers indoors and use your heaviest covers.

Watch the forecast low, sky cover and wind. A forecast of 34°F with clear skies and calm wind is a real frost risk for tender plants, especially in low spots where cold air drains and pools.

Covers that work

Row cover (frost cloth)

Lightweight spun polyester or polypropylene fabric, sold as row cover or frost cloth. It lets light, air and water through, so it can stay on for days if needed. Heavier grades give more protection but let through less light. The protection rating is usually printed on the package, typically a few degrees for light fabrics and more for heavy ones. Drape it over plants or wire hoops and weigh the edges down with soil, bricks or pins so that heat can’t escape and wind can’t lift it.

Sheets, blankets and buckets

Old bedsheets, light blankets, cardboard boxes and upturned buckets or pots all work for a night. Cover in the late afternoon or early evening to trap the day’s heat, and let the cover reach the ground. Use stakes so heavy fabric doesn’t crush plants. Remove these in the morning once temperatures rise above freezing, because they block light.

Cloches and water walls

Individual covers over single plants, such as cut-off plastic jugs with the cap removed for venting, glass cloches, or plastic sleeves filled with water around a tomato. Water walls store heat during the day and release it slowly overnight. Vent or remove cloches on sunny days, because they can overheat quickly.

Cold frames and tunnels

For gardeners who plant early every year, a cold frame or a low tunnel of clear plastic over hoops gives repeat protection. Open it during the day to prevent overheating.

Watering before a frost

Moist soil absorbs more heat during the day and releases it more slowly at night than dry soil. Water the soil around plants in the morning or early afternoon on the day a frost is forecast, not in the evening on the leaves. Combined with a cover, this helps keep the air around plants a little warmer.

What not to do

Don’t let plastic touch leaves. Thin plastic conducts cold, and leaves touching it can freeze. If plastic is all you have, hold it off the plants with stakes or hoops, or put a sheet underneath it.
Don’t leave clear plastic on in the sun. It can cook plants on a sunny morning.
Don’t use open flames or unrated heaters under covers. They are a fire hazard. If you use any electrical heating in a greenhouse or cold frame, follow the manufacturer’s instructions and use outdoor-rated equipment.
Don’t fertilize right before a cold spell. Soft new growth is more easily damaged.

Containers and seedlings

Pots and seed trays lose heat from all sides and freeze faster than plants in the ground. Move them into a garage, shed or the house for the night. Grouping pots together against a south-facing wall and covering them helps if you can’t move them indoors.

The morning after

Remove covers once the temperature is above freezing, especially on a sunny day.
Don’t judge damage straight away. Frost-damaged leaves often look water-soaked, then turn dark or black over a day or two. Wait a few days before pulling plants, because many recover and regrow from undamaged buds.
Trim dead leaves once damage is clear. Replace plants that were killed outright.
Note what happened, with the date and the forecast low, in your garden journal. Over a few seasons that tells you how your own garden compares with the official frost dates.

Avoiding the problem

Plant tender crops after the 10% risk date rather than the median last frost if you would rather not gamble. Your ZIP page shows both. Only about one year in ten has a frost after the 10% date, compared with about one in two after the median.
Harden off transplants so they are tougher when planted out. See hardening off seedlings.
Keep some row cover on hand from early spring onward, so you are ready when a late frost is forecast.
Know your microclimate. Low spots, valley floors and gardens far from buildings or water frost earlier and more often than slopes, cities and lakesides.

Written for SowByZip. Last reviewed 2026-10-20. See about this site for how pages are made.

How to protect plants from a late spring frost