Tomato plants cannot survive hard frost, but they can tolerate light frost depending on the variety and how long the cold lasts
Most tomato plants die when the temperature drops to 32°F (0°C) or below for more than a few hours. The frost damages the plant's cell structure — water inside the cells freezes, ruptures the walls, and kills the tissue. A light frost of 32°F that lasts only an hour or two may not kill an established plant, but a hard freeze of 28°F or lower, or frost that lasts all night, will almost certainly kill the leaves, stems, and fruit.
Some varieties are slightly more cold-tolerant than others — heirloom and cold-hardy types like Siberia, Glacier, and Sub-Arctic Plenty can survive brief dips to 28°F if they are mature and well-established. But even these are not frost-proof. Young seedlings and tender new growth are killed at 40°F. Once a tomato plant is dead from frost, it does not recover.
Key Takeaways
- Tomato plants die when exposed to frost of 32°F or below for more than a few hours; young plants and new growth die at 40°F.
- Frost kills by freezing water inside plant cells, rupturing the cell walls and destroying the tissue permanently.
- Light frost lasting only an hour or two may not kill a mature plant, but hard frost or frost lasting all night will kill the leaves, stems, and fruit.
- You can protect plants from light frost by covering them with cloth, using water jugs, or moving containers indoors before the temperature drops.
- Once a tomato plant is killed by frost, it cannot be revived — prevention is the only option.
How frost damage shows up on tomato leaves and stems
Frost damage appears as blackened, wilted, or mushy tissue on the parts of the plant that were exposed to the cold. Leaves turn dark brown or black and become papery or translucent. The stems may look water-soaked or collapse. If the frost was light, only the newest growth at the tips of branches will be affected; if the frost was hard, the entire plant will be blackened.
Damage is not always visible right away. After a light frost, the plant may look normal for a few hours, then the damaged tissue will darken over the next 12 to 24 hours as the cells break down. If you see blackened leaves the morning after a cold night, the plant has been killed by frost. If only the tips of new growth are darkened and the rest of the plant is still green and firm, the plant may survive and regrow from the undamaged stems below.
Protecting tomato plants from frost before it arrives
The best protection is to know when frost is forecast and cover the plant before the temperature drops. Check your local weather forecast for a frost warning — this means frost is expected within the next 12 hours. Do not wait until the temperature is already cold.
Cover the plant with a frost cloth, bed sheet, burlap, or even newspaper if that is all you have. The cloth traps heat radiating from the soil and keeps the frost from settling on the leaves. Drape it loosely over the plant so it does not touch the leaves — if the cloth touches the frozen leaf, it will conduct the cold and kill the tissue anyway. Anchor the cloth to the ground with rocks, soil, or stakes so the wind does not blow it away. Leave the cover on until the temperature rises above 40°F the next morning, then remove it so the plant can get sunlight.
For container tomatoes, the fastest protection is to move the pot indoors — into a garage, shed, basement, or house — before the frost arrives. Even an unheated garage will stay warmer than the outside air. If you cannot move the pot, wrap the container itself with cloth or blankets to insulate the soil and roots.
Using water and heat sources to prevent frost damage
Water absorbs heat during the day and releases it slowly at night. Placing water-filled containers — gallon jugs, buckets, or even a soaker hose filled with water — around the base of the plant can raise the temperature slightly by a few degrees. This works best on nights when the frost is light (32°F to 35°F) and the day was sunny. On very cold nights, water alone will not be enough.
Some gardeners use incandescent light bulbs or small heaters under frost cloth, but this requires caution: the heat source must not touch the cloth or the plant, and you must monitor it to prevent fire. A safer option is to use a string of outdoor Christmas lights (incandescent, not LED) under the cloth — the bulbs generate enough warmth to raise the temperature a few degrees. This is practical only for small plants or a few containers.
Timing: when to plant tomatoes to avoid frost
The safest approach is to plant tomatoes after the last frost date for your area has passed. The last frost date is the average date of the last frost in spring — it varies by location and can be found through your local cooperative extension office or by searching "[your city] last frost date."
Plant seedlings outdoors only after this date. If you start seeds indoors earlier (which is common, since tomatoes take 6 to 8 weeks to grow from seed to transplant size), keep the seedlings indoors under grow lights until after the last frost date. Hardening off — gradually exposing seedlings to outdoor conditions over 7 to 10 days — helps them adjust, but it does not make them frost-proof.
In fall, frost arrives before winter. The first frost date is the average date of the first frost in autumn. Tomatoes planted in summer will produce fruit until the first frost arrives. If frost is forecast before your tomatoes are ripe, you can cover them to extend the season by a week or two, but eventually the cold will kill the plant.
What to do if frost kills your tomato plant
If the entire plant is blackened and mushy, it is dead and cannot be saved. Remove it from the garden and compost it (or discard it if you prefer). Do not leave a dead plant in the soil — it will rot and may harbor disease or pests.
If only part of the plant is damaged — the top is blackened but the lower stems are still green — cut off the dead growth just above the lowest green leaf or stem. The plant may regrow from the undamaged tissue below, though it will take several weeks and may not produce fruit before the next frost arrives. In most cases, it is faster to pull out the damaged plant and start over with a new seedling if the season is still early enough.
Choosing cold-hardy tomato varieties
Some tomato varieties tolerate cold better than others, though none are truly frost-proof. Cold-hardy varieties include Siberia, Glacier, Sub-Arctic Plenty, Polar, and Coldset. These were bred in or for cold climates and can produce fruit in shorter growing seasons. They still die in hard frost, but they mature faster, so you can harvest ripe fruit before the first frost arrives.
If you live in a region with a short growing season or unpredictable spring frosts, choosing a cold-hardy variety gives you a better chance of a full harvest. Pair this with starting seeds indoors early and protecting young plants with cloth or cloches in spring, and you can extend your tomato season on both ends.
Frequently Asked Questions
Will a tomato plant survive 40°F?
Mature plants with established growth may survive a brief dip to 40°F, but new growth and seedlings will be damaged. Young transplants are killed at 40°F. If the temperature stays at 40°F for more than a few hours, even mature plants will suffer damage to their newest leaves and stems.
Can I save a tomato plant after frost damage?
If only the top growth is blackened and the lower stems are still green and firm, cut off the dead growth and the plant may regrow. If the entire plant is blackened and mushy, it is dead and cannot recover. Remove it and start with a new plant if time allows.
How long can I leave frost cloth on a tomato plant?
Leave the cloth on only as long as the temperature is below 40°F. Remove it once the temperature rises in the morning so the plant gets sunlight and air circulation. Leaving cloth on for more than 24 hours can trap moisture and encourage disease.
Does frost kill tomato fruit on the vine?
Yes. Frost kills the fruit as well as the plant. Green tomatoes will blacken and become mushy. Ripe tomatoes may survive a light frost of 32°F for an hour or two, but hard frost will damage them. Harvest all ripe and nearly ripe fruit before frost is forecast.
What temperature should I bring container tomatoes indoors?
Move containers indoors when frost is forecast — do not wait for the temperature to drop. Even an unheated garage or shed will protect the plant. If you want to keep the plant growing, bring it inside when the nighttime temperature is forecast to drop below 50°F.