Plant tomatoes after your last spring frost, when soil reaches 60°F

The single best time to plant tomatoes is after the danger of frost has passed and the soil has warmed to at least 60°F — ideally 65°F or higher. Tomatoes are warm-season plants and will rot in cold soil or die if exposed to frost after planting. Your local frost date is the key number: it is the average date of the last freeze in your area in spring. You can find your frost date by entering your zip code into the USDA Plant Hardiness Zone Map or by calling your county extension office.

Planting too early is the most common mistake. A tomato planted in 50°F soil will sit dormant and may rot before it grows. Waiting two to three weeks after your frost date gives the soil time to warm and reduces the risk that a late cold snap will kill your seedlings. If you plant in a raised bed or use black plastic mulch to warm the soil, you can plant a few days earlier — but not before the frost date itself.

Key Takeaways

  • Plant tomatoes only after your area's last spring frost date, which you can find through the USDA Plant Hardiness Zone Map or your county extension office.
  • Soil temperature matters more than air temperature — wait until soil reaches at least 60°F, ideally 65°F or warmer.
  • Planting too early in cold soil causes seeds and seedlings to rot rather than grow, so waiting is safer than rushing.
  • Hardening off seedlings (gradually exposing them to outdoor conditions) for 7 to 10 days before planting reduces transplant shock and improves survival rates.
  • In warm climates where frost does not occur, you can plant tomatoes in early spring and again in midsummer for a fall harvest.

How to find your frost date

Your frost date is specific to your location and changes year to year slightly, but the USDA publishes historical averages for every county. Go to planthardiness.ars.usda.gov, enter your zip code, and you will see your hardiness zone and your average last spring frost date. Write this date down — you will use it every year.

If you prefer to call, contact your county extension office directly. They can tell you the frost date and also answer questions about your local soil, water, and pests. Extension offices are free and run by your state's land-grant university. You can find yours by searching "[your state] cooperative extension" online.

Checking soil temperature before planting

Air temperature and soil temperature are not the same. A warm day does not mean the soil is warm. Buy a soil thermometer (they cost $5 to $15 and last for years) and push it 4 inches into the soil in the morning. Check it for three days in a row. If the average is 60°F or higher, the soil is ready.

If you do not have a thermometer, wait until at least one week after your frost date and until daytime air temperatures have been consistently above 70°F for several days. This is a rough guide and less reliable than a thermometer, but it works in most years. In cool springs, soil can stay cold even when the air warms, so the thermometer is worth the small cost.

Hardening off seedlings before planting

If you started tomato seedlings indoors under lights, they are tender and will wilt or die if you move them straight outside. Hardening off means gradually exposing them to outdoor sun, wind, and temperature swings over 7 to 10 days. Start by putting them in a shaded, sheltered spot for 2 to 3 hours, then move them to dappled shade for a few hours the next day, then to partial sun, then to full sun. By day 7 or 8, they can stay outside overnight if temperatures stay above 50°F.

Seedlings that are hardened off will grow faster and stronger than those planted directly from an indoor setup. If you skip this step, expect wilting, leaf burn, and slower growth for the first few weeks. The extra week of preparation pays off in healthier plants.

Planting depth and spacing

Bury tomato seedlings deeper than they were growing in their pots — up to the first true leaves. Tomatoes will grow roots all along the buried stem, creating a stronger root system. Space plants 24 to 36 inches apart, depending on the variety. Determinate (bush) types can be closer; indeterminate (vining) types need more room.

Water the seedling well after planting and keep the soil consistently moist (not soggy) for the first two weeks while roots establish. Mulch around the base with 2 to 3 inches of straw or wood chips, leaving a 2-inch gap around the stem to prevent rot and to keep moisture in the soil.

Planting tomatoes in warm climates

If you live in a warm climate where frost does not occur (USDA zones 10 and 11), you can plant tomatoes in early spring as usual, but you can also plant again in midsummer for a fall and early winter harvest. Summer plantings should go in by mid-July so the plants have time to flower and set fruit before temperatures drop in late fall.

In very hot climates, afternoon shade during the hottest months (June, July, August) can prevent sunscald and keep fruit from splitting. A shade cloth that blocks 30 to 50 percent of sunlight is enough. Once temperatures cool in fall, remove the shade so plants get full sun again.

What to do if frost threatens after planting

If an unexpected frost is forecast after you have planted, cover plants with blankets, burlap, or frost cloth in the late afternoon and remove the cover the next morning when temperatures rise. Do not use plastic sheeting — it conducts cold and can damage plants. Water the soil before covering; moist soil holds heat better than dry soil.

If plants are already in the ground and frost hits before you can cover them, do not panic. Many tomato seedlings can recover from a light frost (32°F to 28°F). Wait a few days before removing damaged leaves — the plant may recover. If the stem is still green and flexible, the plant will likely survive.

Frequently Asked Questions

Can I plant tomatoes before my frost date if I use a cold frame or row cover?

A cold frame or row cover can extend your season by a few weeks, but it does not eliminate frost risk. You still need to wait until soil temperature reaches 60°F. The cover protects seedlings from light frosts (a few degrees below 32°F) but not from hard freezes. Remove covers during warm days to prevent overheating.

What if I plant too early and the seedlings die?

If seedlings rot or freeze, you can replant. You have time — tomatoes planted even in early summer will produce fruit before fall frost in most areas. The delay costs you a few weeks of harvest, but a second planting is better than losing plants to cold soil or frost.

Do I need to wait for the same frost date every year?

The frost date is an average, so the actual last frost varies year to year. Some years it comes early, some years late. Use the historical average as your guide, but watch the weather forecast in late spring. If frost is predicted after you plant, cover your seedlings. Local gardeners and your extension office can tell you if the frost date is running early or late in a given year.

Can I plant tomato seeds directly in the ground instead of starting seedlings indoors?

Yes, but it delays your harvest by 6 to 8 weeks. Seeds need soil at least 70°F to germinate reliably, and they take 7 to 10 days to sprout. Starting seeds indoors 6 to 8 weeks before your frost date and transplanting seedlings after hardening off gives you fruit weeks earlier.

What is the latest I can plant tomatoes and still get a harvest?

Plant by mid-July in most areas to give plants 60 to 80 days to flower and fruit before fall frost. Determinate varieties (which mature all at once) need less time than indeterminate types. Check your variety's days to maturity on the seed packet or plant label, then count backward from your fall frost date.