Start tomatoes indoors 6 to 8 weeks before your last spring frost, or buy seedlings and plant them outside after frost danger passes

The month you plant tomatoes depends on your local frost date, not a calendar date that works everywhere. Tomatoes cannot survive frost — they die at 32°F and below. Your region's last spring frost date is the day after which frost will not return. Plant seedlings outdoors only after that date has passed.

If you start from seed indoors, count backward 6 to 8 weeks from your last frost date. If your last frost is May 15, start seeds indoors around March 15 to April 1. If you buy seedlings from a nursery, you can skip the indoor step and plant them directly outside after your frost date passes.

To find your last frost date, search "[your city or zip code] last frost date" or visit the USDA Hardiness Zone Map. The date varies by hundreds of miles — a gardener in northern Minnesota plants 8 weeks later than one in southern Georgia.

Key Takeaways

  • Tomatoes planted outdoors must go in the ground after your last spring frost date, which varies by region and can be anywhere from late March to late May.
  • If you start from seed indoors, begin 6 to 8 weeks before your last frost date so seedlings are ready to transplant when frost danger ends.
  • Buying seedlings from a nursery skips the indoor step and lets you plant directly outside on or after your last frost date.
  • Tomatoes need soil that has warmed to at least 60°F, ideally 65°F or higher, so waiting until soil temperature rises matters as much as the calendar date.
  • In warm climates with no spring frost, you can plant tomatoes in late winter or early spring and harvest before summer heat peaks.

Indoor seed starting: the 6 to 8 week window

Starting tomato seeds indoors gives you a head start on the growing season and lets you choose varieties that nurseries do not stock. Sow seeds indoors under grow lights or on a sunny windowsill 6 to 8 weeks before your last frost date. Seeds germinate in 5 to 10 days at room temperature and grow into seedlings over the next 4 to 6 weeks.

Water seedlings from below so soil stays moist but not waterlogged. Once seedlings develop their first true leaves (the second set of leaves that appear), thin them to one plant per cell or pot. Seedlings are ready to harden off — gradually expose them to outdoor conditions — about 7 to 10 days before your last frost date. Harden off over 7 to 10 days by setting them outside in a sheltered spot for a few hours each day, then increasing time outdoors until they stay out overnight.

Transplant hardened seedlings into the garden on or after your last frost date. Bury the stem deeper than it was in the pot — tomatoes develop roots along buried stems and grow stronger root systems that way.

Buying seedlings and planting them outside

Nursery seedlings skip the indoor step entirely. Buy them 1 to 2 weeks before your last frost date so you have healthy plants ready to go. Look for stocky seedlings with thick stems and dark green leaves. Avoid leggy seedlings with long, thin stems — they are harder to establish.

Harden off nursery seedlings the same way you would homegrown ones: set them outside in a sheltered spot for a few hours a day, increasing time outdoors over 7 to 10 days. Plant them in the garden on or after your last frost date, burying the stem deeper than it was in the pot.

Soil temperature matters as much as air temperature

Tomato roots grow slowly in cold soil and seedlings sit stunted instead of growing. Soil should be at least 60°F before you plant, ideally 65°F or warmer. A soil thermometer costs $10 to $20 and tells you the actual temperature at root depth — air temperature can be 70°F while soil is still 50°F.

In cool climates, wait 1 to 2 weeks after your last frost date for soil to warm up. In warm climates, soil warms faster and you can plant closer to the frost date. If you plant too early into cold soil, seedlings may rot or grow so slowly that you lose weeks of the growing season.

Planting schedule for different regions

Northern regions (zones 3 to 4): Last frost typically falls between May 15 and June 1. Start seeds indoors in late March or early April. Plant seedlings outdoors in late May or early June after soil warms.

Midwest and mid-Atlantic (zones 5 to 6): Last frost typically falls between April 15 and May 15. Start seeds indoors in February or early March. Plant seedlings outdoors in mid-May to early June.

Southern and warm regions (zones 7 to 9): Last frost typically falls between March 15 and April 15. Start seeds indoors in January or February. Plant seedlings outdoors in March or April. In the hottest zones, you may also plant a second crop in late summer for fall harvest before frost returns.

Tropical and frost-free zones (zone 10+): Plant tomatoes in fall or winter when temperatures cool below 85°F. Spring and summer heat often stops tomato plants from flowering and setting fruit.

Summer heat and fall planting in warm climates

In regions where summer temperatures regularly exceed 90°F, tomato plants stop flowering and drop blossoms even if they are healthy. Pollen becomes sterile above 85°F to 90°F depending on the variety, so fruit does not set. In these climates, plant tomatoes early enough to flower and set fruit before peak heat arrives, or plant a second crop in late summer for fall harvest.

To plant for fall harvest, count backward from your first fall frost date. If your first frost is November 1 and tomatoes need 70 to 85 days to produce fruit, plant in late July or early August. Fall-planted tomatoes often produce better than spring-planted ones in hot climates because they mature as temperatures drop.

Frequently Asked Questions

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

Row covers protect seedlings from light frost but not hard freezes. If your last frost date is May 15 and you plant May 1 under row covers, a frost below 28°F will kill the plants. Row covers work best for extending the season by a week or two, not for planting a month early. Wait until frost danger truly passes.

What if I plant tomatoes too early and frost kills them?

If frost kills seedlings you planted early, you will need to replant. Hardened seedlings recover from light frost (32°F to 35°F) if you cover them, but tender seedlings die. It is faster and cheaper to wait for safe planting dates than to replant after frost damage.

Can I plant tomatoes in summer instead of spring?

In cool climates, no — tomatoes need 70 to 85 days to produce fruit, and planting in July means frost arrives before harvest. In warm climates with long falls, yes — plant in late summer for fall harvest. Check your first fall frost date and count backward to see if you have enough frost-free days left.

Do all tomato varieties have the same planting window?

All tomatoes need to be planted after frost danger passes, but some varieties mature faster than others. Early varieties produce fruit in 60 to 70 days, while late varieties need 80 to 90 days. In short-season climates, choose early varieties and plant as soon as frost passes. In long-season climates, you can plant later varieties.