Plant tomatoes after your last spring frost, when soil reaches 60°F and daytime temperatures stay above 50°F

The single most important date for tomato planting is your area's last spring frost date. Tomatoes are killed by frost, so planting before that date means your seedlings will die. You can find your frost date by searching "[your city] last frost date" or by checking the USDA Hardiness Zone Map, which lists frost dates by region.

Beyond the frost date, soil temperature matters as much as air temperature. Tomato seeds and transplants sit dormant or rot in cold soil. Soil should reach at least 60°F before you plant; 65°F to 70°F is better. You can check soil temperature with an inexpensive soil thermometer from any garden center. If you plant too early, the seeds won't germinate, and transplants will just sit there for weeks.

In most of the United States, this means planting between mid-April and late May, depending on where you live. In warmer regions (southern Florida, southern Texas, southern California), you may plant in late winter or early spring. In cooler regions (northern New England, the upper Midwest), you wait until late May or early June.

Key Takeaways

  • Your last spring frost date is the hard important date—tomatoes planted before that will be killed by frost, so check your local date before you buy seedlings.
  • Soil temperature must reach 60°F or higher; air temperature alone is not enough, and cold soil causes seeds to rot and transplants to stall.
  • Seedlings started indoors should be 6 to 8 weeks old and hardened off (gradually exposed to outdoor conditions) before transplanting outside.
  • If you miss the spring window, many regions allow a second planting in mid-summer for a fall harvest, timed so fruit matures before the first fall frost.

How to find your last frost date

The easiest method is to search your city name plus "last frost date." The National Weather Service publishes these dates for thousands of locations. You can also enter your zip code into the USDA Hardiness Zone Map at planthardiness.ars.usda.gov, which shows your zone and typical frost dates.

If you live near a botanical garden, university extension office, or large local nursery, staff can tell you the date from memory. Many nurseries also post it on their website or in-store. The date is usually accurate to within a few days year to year, though frost can arrive earlier or later than average.

Soil temperature vs. air temperature

Air temperature and soil temperature are not the same. A warm day in April might reach 70°F in the air while soil is still 45°F. Tomatoes need warm soil to germinate and to grow roots. Cold soil triggers rot in seeds and causes transplants to sit stunted for weeks, wasting time and money.

Buy a soil thermometer (they cost $5 to $15) and check the soil in the morning, 4 inches deep, in the spot where you plan to plant. Check it for three days in a row. Once it stays at 60°F or above, you can plant. If you don't have a thermometer, wait until daytime air temperatures have been above 60°F for at least a week and nighttime lows stay above 50°F.

Starting seeds indoors vs. buying transplants

If you start seeds indoors, sow them 6 to 8 weeks before your last frost date. This gives seedlings time to grow strong before transplanting outside. Seeds started too late will be small and weak when frost date arrives; seeds started too early will be overgrown and leggy by planting time.

If you buy transplants from a nursery, plant them outside after your frost date and once soil is warm. Nursery seedlings are usually 4 to 8 weeks old already, so they're ready to go into the ground right away. Harden them off first—set them outside in a sheltered spot for a few hours a day for 3 to 5 days—so they adjust to wind and direct sun before planting.

Planting in containers vs. in-ground beds

Container soil warms faster than ground soil because it's exposed to sun on all sides. You can plant tomatoes in containers 1 to 2 weeks earlier than in-ground beds, as long as soil temperature in the pot reaches 60°F. Use a pot at least 5 gallons for determinate varieties and 10 gallons for indeterminate (vining) types.

In-ground beds take longer to warm because they're surrounded by cooler earth. If your soil is heavy clay, it warms even more slowly. You can speed this up by laying black plastic or landscape fabric over the bed for 2 to 3 weeks before planting—the dark surface absorbs heat and warms the soil underneath.

Second plantings for fall harvest

Many regions allow a second tomato planting in mid-summer for a fall harvest. Count backward from your first fall frost date (the date frost typically arrives in autumn). Tomatoes need 60 to 85 days from transplant to first ripe fruit, depending on variety. Plant so that fruit will mature before frost arrives.

For example, if your first fall frost is October 15, and you want 70 days to maturity, plant by mid-August. This gives you a second crop in September and October. Summer heat can slow germination and seedling growth, so buy transplants rather than starting seeds; they're faster and more reliable in heat.

What happens if you plant too early

Planting before soil reaches 60°F causes seeds to rot in the ground. Transplants sit dormant, their roots don't grow, and they may yellow or wilt. You lose weeks of growing time. If you plant before the last frost date, a late frost will kill the seedlings outright, and you'll have to replant anyway.

The temptation to plant early is strong—nurseries sell seedlings in March and April, and the weather feels warm on a sunny day. Resist it. Waiting one or two weeks for soil to warm saves you from replanting and gives you healthier, faster-growing plants.

Frequently Asked Questions

Can I plant tomatoes if the air is warm but soil is still cold?

No. Cold soil causes seeds to rot and transplants to stall. Even if daytime air reaches 70°F, soil temperature is what matters for root growth. Wait until soil reaches 60°F, even if it means waiting another week or two after the last frost date.

What if I plant too late and miss the window?

If you miss spring planting, you can still plant for fall harvest in mid-summer, as long as you have 60 to 85 days before the first fall frost. Buy transplants rather than seeds—they grow faster in summer heat. Check your fall frost date first to make sure you have enough time.

Do I need to harden off seedlings I started indoors?

Yes. Indoor seedlings are soft and pale because they've been in stable, protected conditions. Hardening off—setting them outside for a few hours a day for 3 to 5 days—toughens them up and prepares them for wind, direct sun, and temperature swings. Skip this step and transplants will wilt or sunburn.

Does the variety of tomato change when I should plant?

No. All tomato varieties need the same frost date and soil temperature to survive and grow. Determinate (bush) and indeterminate (vining) types both go in the ground after the last frost date and when soil is warm. Variety affects how long fruit takes to mature, which matters for fall planting, but not for spring timing.

Can I plant tomatoes in a greenhouse earlier than outdoors?

Yes. A greenhouse traps heat and protects from frost, so you can plant 2 to 4 weeks earlier than outdoors. Soil in a greenhouse warms faster, and seedlings are sheltered from wind and cold nights. You still need to harden them off if you move them outside later.