Winterizing tomato plants means protecting them from frost and cold by either moving them indoors, covering them, or harvesting before the freeze

Tomato plants die when temperatures drop below 50°F, and frost kills them outright. Winterizing is your choice of three paths: bring potted plants inside, cover plants in the ground with blankets or row covers, or harvest all remaining fruit before the first frost date arrives in your area. Which path you take depends on whether your tomatoes are in containers, how much frost protection you want to attempt, and whether you're willing to keep plants alive indoors through winter or straightforward want to save the fruit.

The timing matters more than the method. Frost can arrive suddenly, so start watching your local weather forecast in late summer. Most areas have a predictable first frost date — the average date when the first freeze happens — but it varies by region and even by neighborhood. You can find yours by searching "[your city] first frost date" or asking your local cooperative extension office.

Key Takeaways

  • Tomato plants stop growing and die when exposed to temperatures below 50°F, so you must act before frost arrives in your area.
  • Potted tomatoes can be moved indoors to a sunny window or grow light and will produce fruit slowly through winter if temperatures stay above 55°F.
  • In-ground tomatoes can be covered with blankets, row covers, or cloches on frost nights, but this only buys a few weeks and works best for light frosts, not hard freezes.
  • Harvesting all fruit before the first frost date is the simplest method and works whether tomatoes are ripe, mature green, or still small.
  • Green tomatoes picked before frost will ripen indoors at room temperature over two to four weeks if stored in a paper bag or cardboard box.

Moving potted tomatoes indoors for winter production

If your tomatoes are in containers, you can bring them inside before frost and keep them producing through winter. Choose a location with at least six hours of direct sunlight daily — a south-facing window works best. If natural light is weak, a grow light positioned 6 to 12 inches above the plant will sustain growth. Keep the temperature between 55°F and 75°F; below 55°F, the plant stops growing and fruit production slows dramatically.

Water when the top inch of soil feels dry to your touch. Indoor air is drier than outdoor air, so check more often than you did outside — usually every two to three days. Fertilize every two weeks with a balanced fertilizer (equal parts nitrogen, phosphorus, and potassium) because indoor plants don't get the nutrient boost that rain and soil microbes provide outdoors. Indoors, pollination happens less reliably, so gently shake the plant when flowers open to help pollen move between flowers, or use a small brush to move pollen by hand.

Inspect the plant before bringing it inside. Check the underside of leaves and the stem base for spider mites, whiteflies, and other pests that thrive indoors. Spray the plant with insecticidal soap if you see any, or isolate it for a few days to watch for pest activity before placing it near other houseplants.

Covering in-ground tomatoes on frost nights

Row covers, blankets, and cloches trap heat radiating from the soil and can protect plants from light frost (32°F to 35°F) for one or two nights. This method buys time but does not work for hard freezes (below 28°F) or sustained cold. Use it when the forecast calls for a single frost night followed by warmer weather, not when cold is expected to linger.

Drape frost cloth or an old bedsheet directly over the plant and anchor it to the ground with soil, rocks, or stakes so wind doesn't blow it away. Remove the cover during the day if temperatures rise above 50°F, or the plant will overheat. Cloches — clear plastic or glass domes placed over individual plants — work the same way but are easier to manage because you don't have to remove them by hand each morning. Water the soil before covering; moist soil holds heat better than dry soil.

This approach works best for plants with only a few weeks of growth left. If frost is forecast to return repeatedly, covering becomes impractical, and you'll save time and effort by harvesting instead.

Harvesting fruit before the first frost date

The simplest winterizing method is to pick all tomatoes before frost arrives. This works whether fruit is fully ripe, mature green (full-sized but still green), or even smaller. Mature green tomatoes — those that have reached full size but haven't started to color — will ripen indoors. Smaller fruit may not ripen well and is better used for cooking or composted.

Pick fruit gently, holding the stem and twisting slightly until it separates from the plant. Leave the stem attached to the tomato if possible; it helps the fruit last longer. Wash and dry each tomato, then place it in a single layer in a cardboard box or paper bag. Store at room temperature (68°F to 72°F is ideal) in a location out of direct sunlight. Check every few days and remove any fruit that shows soft spots or mold.

Ripe tomatoes will ripen within a few days. Mature green tomatoes take two to four weeks. You can speed ripening slightly by placing a ripe banana or apple in the box with them — the ethylene gas they release encourages ripening — but temperature matters more than anything else. Below 55°F, ripening slows or stops. Above 75°F, the fruit may develop soft spots before it colors.

Preparing plants in the ground for frost

If you plan to cover plants rather than harvest, prepare the soil and plant structure a few days before frost is forecast. Water deeply so the soil is moist but not waterlogged; wet soil holds heat better than dry soil. Prune off any dead or diseased leaves, which can rot under a cover and spread disease. Leave healthy foliage intact — it protects the fruit and stem.

If your tomato plant is tall and spindly, stake or cage it securely before covering. A cover adds weight and wind resistance, and a plant that tips over will break. Check stakes and ties to make sure they're tight but not so tight they cut into the stem.

Deciding between methods based on your situation

Choose harvesting if frost is forecast within a week and you want the simplest approach. This works for any tomato plant and requires no special equipment. Choose covering if frost is light and brief, and you have only a few weeks of growing season left — the effort is worth it if you'll gain two or three weeks of production. Choose moving indoors only if your tomatoes are in pots and you have a sunny window or grow light; this method demands the most attention but can extend your harvest through winter.

If you're unsure whether frost is coming, check your local cooperative extension office website or call your county extension agent. They can tell you the average first frost date for your area and whether an early frost is possible. Many also offer frost forecasts during late summer and fall.

What to do with harvested green tomatoes

Green tomatoes that don't ripen indoors can be used in cooking. Fried green tomatoes are a traditional Southern dish. Green tomatoes can also be pickled, made into relish, or added to salsa. If you have many green tomatoes and don't want to cook with them, you can compost them — they break down like any other plant material.

Tomatoes that show a slight blush of color (the first hint of red or orange) will ripen indoors more reliably than completely green fruit. If you're harvesting a large plant with hundreds of small green tomatoes, focus on picking the larger ones and the ones showing early color; smaller fruit is unlikely to ripen well and takes up storage space.

Frequently Asked Questions

Can I leave tomato plants outside and just hope they survive the cold?

No. Tomato plants are killed by frost and cannot survive freezing temperatures. Even a light frost (32°F) will damage or kill the plant. If you want to keep the plant alive, you must move it indoors, cover it, or harvest before frost arrives.

How long can I keep covering a plant before I have to harvest?

Covering works for a few frost nights, but if frost is forecast repeatedly over several weeks, the effort becomes impractical and the plant will eventually decline. Most gardeners cover for one or two frost events, then harvest if cold weather persists. Check your forecast two weeks ahead to decide whether covering is worth the time.

Do green tomatoes ripen faster if I put them in the sun?

No. Tomatoes ripen based on temperature and ethylene gas, not light. In fact, direct sunlight can cause soft spots and uneven ripening. Store them in a cool, dark place at room temperature for best results.

What temperature should I keep indoor tomatoes at?

Between 55°F and 75°F is ideal. Below 55°F, growth slows and fruit production drops. Above 75°F, the plant may wilt and fruit can develop soft spots. A typical heated home stays in this range, so a sunny window usually works fine.

Can I save seeds from tomatoes I harvested before they were ripe?

Seeds from mature green tomatoes that ripen indoors are viable and will grow. However, if you're saving seeds from hybrid tomatoes (most store-bought varieties), the seeds won't produce plants identical to the parent. Heirloom and open-pollinated varieties produce seeds that grow true to type.