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

The best time to plant tomatoes is after the last spring frost in your area and when soil temperature hits at least 60°F—ideally 65°F or warmer. Tomatoes are warm-season plants that will rot in cold soil and stop growing if air temperatures drop below 50°F at night. Planting too early is the most common mistake home gardeners make, and it wastes weeks because the seeds straightforward sit dormant underground.

To find your last frost date, search "[your city] last frost date" or check the USDA Hardiness Zone Map at planthardiness.ars.usda.gov. This date varies dramatically by region—it might be mid-April in Georgia, late May in Minnesota, or early June in Alaska. Your local cooperative extension office (search "[your county] cooperative extension") can also tell you the exact date for your area.

Soil temperature matters more than air temperature. A soil thermometer costs $8 to $15 and takes the guesswork out. Push it 4 inches into the ground in the morning. If it reads below 60°F, wait another week and test again. Air temperature can fool you—a warm day in April doesn't mean the soil has warmed up.

Key Takeaways

  • Plant tomatoes outdoors only after your last spring frost date and when soil temperature reaches 60°F or higher, measured 4 inches deep.
  • Starting seeds indoors 6 to 8 weeks before your last frost date lets you transplant seedlings at the right time instead of waiting for warm soil.
  • Tomatoes planted too early will sit in cold soil and may rot; those planted in warm soil grow faster and produce earlier in the season.
  • A soil thermometer is the most reliable way to know when to plant, since air temperature and soil temperature are often very different.

How to count backward from your last frost date

If you want to start seeds indoors (which most gardeners do), count backward 6 to 8 weeks from your last frost date. This gives seedlings time to grow strong enough to transplant outside without becoming leggy or root-bound. For example, if your last frost date is May 15, start seeds indoors around March 20 to April 1.

Mark this date on a calendar now. Tomato seeds need warmth to germinate—keep them at 70°F to 80°F under grow lights or on a sunny windowsill. They sprout in 5 to 10 days. Once seedlings have their first true leaves (the second set that appears), move them under bright light to prevent them from stretching toward the window.

If you buy seedlings from a nursery instead of starting from seed, you can plant them outdoors closer to your last frost date, since they are already 4 to 6 weeks old. Harden them off first by setting them outside in a sheltered spot for 1 to 2 hours, then gradually increase outdoor time over a week. This prevents transplant shock.

Soil temperature and nighttime air temperature

Tomato roots need warm soil to absorb water and nutrients. In cold soil below 55°F, roots cannot take up phosphorus, which stunts growth and delays flowering. Soil warms more slowly than air, especially in spring. A sunny day in April might reach 70°F in the air while soil stays at 50°F just 4 inches down.

Nighttime temperatures matter as much as daytime ones. Tomato plants stop growing when nighttime temperatures drop below 55°F and suffer damage below 32°F. Check the forecast for the next 2 weeks after planting. If a frost is predicted, cover plants with a frost cloth or move potted seedlings indoors overnight.

In cool climates, warm the soil before planting by laying black plastic mulch over the bed 1 to 2 weeks early. The plastic traps heat and can raise soil temperature by 5 to 10°F. Remove it once plants are in the ground and cover the soil with regular mulch to retain moisture.

Regional planting windows

Planting dates shift across the country. In warm zones (USDA 9 and 10), you may plant tomatoes in late winter or early spring, and again in mid-summer for a fall harvest. In moderate zones (USDA 6 to 8), plant in spring after frost danger passes. In cold zones (USDA 3 to 5), the window is narrow—often just 2 to 3 weeks in late May or early June.

Southern gardeners sometimes plant tomatoes twice: once in spring for a summer harvest, and again in late July or August for a fall crop. The second planting avoids the hottest part of summer, when tomato flowers drop and fruit stops setting. Check with your local extension office about whether a fall crop makes sense in your area.

If you live in a very short-season area, choose early-maturing varieties like 'Early Girl' (50 to 60 days to harvest) or 'Siberia' (55 to 65 days) instead of long-season types like 'Brandywine' (70 to 85 days). Starting seeds indoors becomes even more important because you need every warm day to count.

What happens if you plant too early

Planting tomatoes in cold soil causes seeds to rot before they sprout. If seedlings do emerge, they sit stunted and vulnerable to fungal diseases like damping-off, which kills them at the soil line. Even if they survive, they grow so slowly that you lose weeks of growing time—the opposite of what you hoped to gain by planting early.

Cold-stressed tomato plants also attract pests. Weak seedlings cannot fight off spider mites or whiteflies. A plant that should be flowering by mid-June might still be small and struggling in July, cutting your harvest window short.

The temptation to plant early is strong in spring, especially after a long winter. Resist it. Waiting one more week for soil to warm up saves you from replanting and gives you a stronger, faster-growing plant.

Extending the season at both ends

To harvest tomatoes earlier, start seeds indoors on schedule and use row covers or cloches (clear plastic domes) to warm the air around young plants for the first 2 to 3 weeks after transplanting. Remove covers once nighttime temperatures stay above 50°F.

To extend the harvest into fall, stop pinching off new flower clusters by late July or early August (depending on your region). This lets the plant focus energy on ripening fruit already on the vine instead of making new flowers that won't mature before frost. In early fall, when nighttime temperatures drop below 60°F, tomatoes ripen more slowly, so pick them at the breaker stage (when the first blush of color appears) and ripen them indoors on a windowsill.

In late summer, prune suckers and lower leaves to direct energy to ripening fruit and improve air circulation, which reduces disease. Stop fertilizing 4 to 6 weeks before your first expected frost so the plant puts energy into fruit rather than new growth.

Using a soil thermometer correctly

A soil thermometer removes all guesswork. Buy one with a dial or digital readout—they cost $10 to $20 and last for years. Test soil in the morning, when temperature is most stable. Push the probe 4 inches into the ground in the spot where you plan to plant. Wait 2 minutes for an accurate reading.

Test in at least three spots across your garden, since soil warms unevenly. A sunny, south-facing bed warms faster than a shaded area. If one spot reads 65°F and another reads 55°F, plant in the warm spot first and wait another week for the cooler area.

Check soil temperature again 3 to 5 days after your last frost date. Even if the date has passed, soil might still be cold. Waiting for the thermometer to confirm 60°F or higher is the single most reliable way to time planting right.

Frequently Asked Questions

Can I plant tomatoes before the last frost date if I use row covers?

Row covers help, but they do not replace warm soil. Covers trap heat and can protect plants from a light frost, but they cannot warm soil that is still below 60°F. Plant when soil is warm enough, then use covers to protect against unexpected cold snaps in the first few weeks.

What if I plant seedlings and a frost is forecast?

Cover plants with frost cloth, blankets, or even cardboard boxes before sunset. Remove covers the next morning once temperatures rise above freezing. Water plants before covering them—moist soil holds heat better than dry soil. If frost damage occurs, wait a few days before removing damaged leaves; the plant may recover.

Is it better to plant seeds directly in the ground or start them indoors?

Starting indoors is faster and more reliable for most gardeners. Seeds germinate better in warm, controlled conditions, and seedlings are ready to transplant right when soil warms up. Direct seeding works in warm climates with long growing seasons, but in cooler areas you lose too much time waiting for soil to warm.

Do all tomato varieties have the same planting time?

Yes—all tomatoes need the same soil and air temperatures to thrive. The difference is how long they take to produce fruit after planting. Early varieties mature in 50 to 65 days; main-season types take 65 to 80 days. Plant all of them at the same time, but choose early varieties if your growing season is short.

Can I plant tomatoes in containers instead of the ground?

Yes, and containers warm up faster than garden soil. A 5-gallon pot of potting mix can reach 60°F a week or two before ground soil does. Use dark-colored containers to absorb more heat. Containers dry out faster in summer, so water daily once plants are established.