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

The single most important date for tomatoes is your last spring frost date. Tomatoes cannot survive frost—even a light frost will kill seedlings or young plants. You need to know this date for your specific location, not a general region, because frost dates vary by elevation and proximity to water.

Find your last frost date by searching "[your city] last frost date" or visiting the USDA Plant Hardiness Zone Map at planthardiness.ars.usda.gov. Enter your zip code and you will see your zone. From there, you can find the average last frost date for your area. This is the date after which frost is unlikely but not impossible—a 10 percent chance remains. If you plant before this date, you are gambling.

Soil temperature matters as much as air temperature. Tomato seeds germinate poorly below 60°F and will rot in cold, wet soil. Even if the air is warm, check soil temperature with a straightforward soil thermometer (under $10 at any garden center). Wait until soil consistently reads 60°F or higher before planting seeds or transplants directly in the ground.

Key Takeaways

  • Plant tomatoes only after your last spring frost date, which you can find by entering your zip code into the USDA Plant Hardiness Zone Map.
  • Soil temperature must reach 60°F or higher; air temperature alone is not enough, and cold soil causes seeds to rot.
  • Start seeds indoors 6 to 8 weeks before your last frost date if you want mature transplants ready to go into the ground on planting day.
  • In hot climates, you may plant a second crop in late summer for a fall harvest, timing it so fruit matures before the first fall frost.
  • Hardening off—gradually exposing indoor seedlings to outdoor conditions—takes 7 to 10 days and must happen before transplanting.

Starting seeds indoors versus buying transplants

You have two paths: start seeds indoors under lights, or buy seedlings from a nursery and transplant them. Starting indoors gives you more variety and costs less per plant, but requires space, lights, and attention. Buying transplants is faster and simpler if you only need a few plants.

If you start seeds indoors, sow them 6 to 8 weeks before your last frost date. This timing ensures seedlings are sturdy and have their first true leaves by the time soil is warm enough to plant them outside. Seeds started too early become leggy (tall and weak) while waiting for warm soil. Seeds started too late will still be tiny when planting day arrives.

Nursery transplants are usually ready to plant as soon as soil warms, so you do not need to plan as far ahead. However, you are limited to whatever varieties the nursery stocks. If you want heirloom or unusual varieties, starting your own seeds is often the only option.

Hardening off seedlings before transplanting

Seedlings grown indoors under lights are soft and tender. Moving them directly from your kitchen to full outdoor sun will shock them—leaves will bleach white, growth will stall, and plants may die. Hardening off is the process of gradually exposing seedlings to outdoor conditions over 7 to 10 days.

Start by placing seedlings in a sheltered, shaded spot outdoors for 2 to 3 hours. Each day, increase the time outside and gradually move them into more sunlight. By day 7 or 8, they should tolerate full sun and outdoor temperature swings. On the final day or two, leave them outside overnight if temperatures stay above 50°F. This slow transition toughens the plant tissue and prevents transplant shock.

If you skip hardening off or rush it, seedlings will wilt, stop growing, or die even if soil and air temperature are ideal. The extra week is not optional—it is the difference between a plant that thrives and one that struggles all season.

Regional planting windows across the United States

Last frost dates range from mid-February in southern Florida and southern Texas to late May or early June in northern states and high elevations. This means planting windows vary dramatically. A gardener in Georgia might plant in mid-April, while a gardener in Minnesota waits until mid-May.

Warm-climate gardeners (zones 9 and 10) have a second opportunity: a fall planting window. You can plant tomatoes in late summer—typically July or August—so they mature before the first fall frost. This second crop often produces better fruit because it avoids the hottest part of summer. Calculate backward from your first fall frost date, allowing 60 to 85 days for the variety you choose to reach maturity.

If you live in a very short-season area (zone 3 or 4), choose early-maturing varieties that produce fruit in 55 to 70 days rather than 80 to 90 days. Start seeds indoors as early as late February so transplants are large and established by planting day. Even then, you may need to use row covers or cloches to protect young plants from unexpected late frosts.

Soil preparation before planting day

Tomatoes are heavy feeders and need rich soil. Before planting, work compost or aged manure into the top 8 to 10 inches of soil. This improves drainage, adds nutrients, and helps soil retain moisture during dry spells. If your soil is clay-heavy or compacted, adding 2 to 3 inches of compost makes a real difference in plant health and yield.

A soil test from your local cooperative extension office (search "[your county] cooperative extension soil test") tells you what nutrients your soil lacks and what pH adjustments it needs. Tomatoes prefer slightly acidic soil with a pH between 6.0 and 6.8. If your soil is too alkaline, sulfur can lower pH; if it is too acidic, lime can raise it. These corrections take weeks to work, so do a soil test in fall or early spring, not the week before planting.

Protecting young plants from late frost

Even after you plant, frost can return unexpectedly. Keep frost cloth, row covers, or old blankets on hand. If frost is forecast within a week of planting, cover plants in the evening and remove covers the next morning when temperature rises. A straightforward tomato cage draped with frost cloth provides several degrees of protection.

Water plants thoroughly before a frost warning. Moist soil holds heat better than dry soil and radiates it back to plants during the night. Avoid fertilizing young plants right before a frost—new growth is tender and more vulnerable to cold damage.

Frequently Asked Questions

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

Row covers provide some protection, but they are not reliable for frost. If temperatures drop below 32°F, frost cloth alone will not save plants. Plant after your last frost date to avoid the risk. Row covers are better used to extend the season in fall or to protect plants from insects in early summer.

What if my area has an unpredictable spring with late frosts?

Wait until soil reaches 60°F and at least one week has passed since your last frost date. This gives you a safety margin. If frost does occur, you can cover plants or replant if necessary. Planting too early and losing everything is worse than planting a week late and having healthy plants.

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

Container soil warms faster than ground soil because it is exposed to sun on all sides. You can plant containers a week or two earlier than in-ground beds, but still wait until soil temperature reaches 60°F. Use a potting mix, not garden soil, and may support containers have drainage holes.

Is it too late to plant if I missed the spring window?

In most of the United States, yes—you would not have time for fruit to mature before fall frost. In warm climates (zones 9 and 10), you can plant a fall crop in late summer. Check your first fall frost date and count backward 70 to 85 days to see if you have time.

Do I need to wait for nighttime temperatures to stay warm?

Nighttime temperatures below 55°F slow tomato growth and can cause flower drop even if daytime temperatures are warm. Wait until nighttime lows consistently stay above 55°F for best results. This usually happens a week or two after your last frost date.