Plant tomatoes after your last frost date, when soil temperature reaches 60°F and ideally 65°F or warmer

The single most important date for tomato planting is your last spring frost date. Tomatoes cannot survive frost. A frost after you plant will kill seedlings or young plants outright. Find your last frost date by entering your zip code into the USDA Plant Hardiness Zone Map or asking your local cooperative extension office — the date varies by hundreds of miles and can shift by weeks depending on elevation and proximity to water.

Soil temperature matters as much as air temperature. Tomato seeds and transplants planted into cold soil will sit dormant, rot, or grow so slowly that pests and disease catch up. Wait until soil reaches at least 60°F; 65°F or higher is better. You can measure soil temperature with a soil thermometer pushed 4 inches into the ground in the morning. Soil warms more slowly than air, so even if daytime air hits 70°F, soil may still be in the 50s.

The timing also depends on whether you are starting from seed indoors, buying transplants, or direct-seeding into the ground. Each method has a different window.

Key Takeaways

  • Plant tomato transplants outdoors after your last frost date and when soil temperature reaches 60°F to 65°F, which usually falls 1 to 3 weeks after the frost date.
  • Start seeds indoors 6 to 8 weeks before your last frost date so transplants are ready to go into the ground at the right time.
  • Direct-seed tomatoes into warm soil only in short-season areas, and only varieties that mature in 60 to 70 days or less.
  • In hot climates, plant a second crop in mid to late summer for a fall harvest, timing it so fruit matures before the first fall frost.
  • Soil temperature is more reliable than air temperature — use a thermometer rather than guessing by the calendar.

Starting seeds indoors: the 6 to 8 week window

If you are growing tomatoes from seed, start them indoors 6 to 8 weeks before your last frost date. This gives seedlings time to develop true leaves and a sturdy stem before transplanting outdoors. Starting too early produces leggy, weak plants that struggle after planting. Starting too late means transplants are still tiny when the soil is warm enough to plant.

Sow seeds in seed-starting mix under grow lights or in a bright window. Keep soil moist but not waterlogged. Seedlings emerge in 5 to 10 days at 70°F to 75°F. Once they have their first true leaves (the second set to appear), thin them or move each to its own small pot. About 2 weeks before your last frost date, begin hardening off — moving plants outdoors for a few hours each day in a sheltered spot, gradually increasing time outside over 7 to 10 days. This toughens them for outdoor conditions.

Transplant hardened-off seedlings into the garden after the last frost date and when soil is warm. Bury them deeper than they grew in pots — tomatoes root along buried stems and develop stronger root systems that way.

Buying transplants: timing the purchase

If you buy transplants from a nursery or garden center, time your purchase for 1 to 2 weeks before your last frost date. This gives you time to harden them off at home before planting. Many garden centers sell tomato transplants in early spring, and the temptation is to buy and plant them when ready — resist it. Plants sitting in a warm greenhouse are not ready for outdoor conditions.

Harden off purchased transplants the same way: move them to a sheltered outdoor spot for a few hours daily, increasing time outside over a week. Then plant them in the garden after the last frost date and when soil temperature is 60°F or higher. If you cannot harden them off, wait until soil is warmer — 65°F to 70°F — to reduce transplant shock.

Avoid buying transplants that are already flowering or heavily budded. Young plants with just leaves and a strong stem establish faster and produce more total fruit than plants that flower before planting.

Direct seeding into the ground: only for warm climates

Direct seeding — planting seeds straight into garden soil — works only in areas with a long growing season and warm soil. Sow seeds directly into the ground only after soil reaches 65°F and stays there. In most of the United States, this is 2 to 4 weeks after the last frost date. In short-season areas, direct seeding is risky because seeds may rot in cool soil or germinate so late that plants do not mature before fall frost.

If you direct-seed, choose varieties that mature in 60 to 70 days or less. Plant seeds 1/4 inch deep, 2 to 3 inches apart, in rows or clusters. Thin seedlings to 24 to 36 inches apart once they have true leaves. Direct-seeded plants often catch up to transplants by mid-summer, but they skip the early growth stage and may produce slightly later than transplanted seedlings.

Planting a second crop in hot climates

In areas with hot summers and mild falls — much of the South and Southwest — you can plant a second tomato crop in mid to late summer for a fall harvest. The timing works backward from your first fall frost date. Count back the number of days your variety needs to mature, then subtract 2 weeks as a buffer. That is when to plant.

For example, if your first fall frost is October 15 and your variety matures in 75 days, plant around July 20. This gives the plant time to set fruit before temperatures drop and days shorten. Choose the same varieties you grew in spring — they are proven in your climate — or try heat-tolerant types if spring plants struggled in peak summer heat.

Summer-planted tomatoes often produce less total fruit than spring plantings because they mature in shorter days and cooler temperatures. But in climates where summer heat kills spring plants, a fall crop is the better option.

Adjusting for your specific climate

Frost date is a starting point, not the whole story. In areas with cool springs, soil may not reach 65°F until 3 or 4 weeks after the last frost date. In areas with early summer heat, you might plant as soon as soil hits 60°F. Coastal regions stay cool longer than inland areas at the same latitude. High elevation means later planting than low elevation nearby.

The most reliable approach is to check soil temperature weekly starting 2 weeks before your frost date. Once it hits your target — 60°F for transplants, 65°F for seeds — you are ready. Waiting for soil to warm is not lost time; cold soil slows growth far more than planting a week or two later into warm soil.

Ask your local cooperative extension office or experienced gardeners in your area what date they typically plant. They have years of local data and can tell you whether your frost date is early or late in your specific neighborhood.

Common planting mistakes and how to avoid them

The most common mistake is planting too early because the calendar says spring has arrived or because neighbors are planting. Tomatoes planted into soil colder than 60°F sit still for weeks, giving pests and disease time to take hold. They often produce less total fruit than plants that go in 2 weeks later into warm soil.

The second mistake is buying transplants too early and letting them outgrow their pots while waiting for planting time. Overgrown transplants are root-bound and stressed before they even go in the ground. Buy them 1 to 2 weeks before you plan to plant, not 4 to 6 weeks early.

A third mistake is planting seedlings that are too tall and leggy. This usually means they did not get enough light indoors. Leggy plants are weaker and more prone to disease. If your seedlings are tall and thin, bury them deeper when transplanting — they will root along the buried stem and develop a stronger plant.

Frequently Asked Questions

Can I plant tomatoes before the last frost date if I cover them?

Frost cloth or row covers do protect plants from light frost, but they require monitoring and removal on warm days. It is simpler and safer to wait until after the last frost date. If you plant early and frost is forecast, covers work as emergency protection, but they are not a substitute for proper timing.

What if my soil is still cold but the calendar says I should plant?

Trust the soil temperature, not the calendar. Cold soil causes more problems than planting a few weeks late. Use a soil thermometer to check, and wait until soil reaches 60°F to 65°F. Plants in warm soil grow faster and produce more than plants sitting in cold soil waiting to wake up.

How do I know if my transplants are ready to plant?

Transplants are ready when they have several sets of true leaves, a sturdy stem, and roots visible at the bottom of the pot. They should be 6 to 8 inches tall. Avoid transplants that are already flowering — they establish slower and produce less total fruit than younger plants.

Can I plant tomatoes in containers on a different schedule than in-ground?

Container soil warms faster than ground soil, so you can plant containers 1 to 2 weeks earlier than in-ground beds. But the same rules explore: wait until soil temperature in the container reaches 60°F, and harden off transplants before planting. Containers also dry out faster, so you will water more often than in-ground plants.

What happens if I plant too late in the season?

Late-planted tomatoes produce fewer total fruits because they mature in shorter days and cooler fall temperatures. If you plant after mid-summer in most climates, fruit may not ripen before the first fall frost. Choose fast-maturing varieties (60 to 70 days) if you are planting late, and accept a smaller harvest.