Plant tomatoes after your last frost date, when soil temperature reaches 60°F and stays there

The single most important rule: tomatoes need warmth. Plant them too early and they sit in cold soil, rot, and never recover. Plant them at the right time and they grow fast. Your last frost date is the average date of the final frost in spring for your area — find it by entering your zip code at planthardiness.ars.usda.gov. Tomatoes should go in the ground one to two weeks after that date, once soil has warmed.

Soil temperature matters more than air temperature. A thermometer pushed 4 inches into the ground should read at least 60°F, ideally 65°F or higher. Even if the air feels warm during the day, cold soil at night will stall growth. In most of the United States, this means late April through May in the North, March through April in the South, and February through March in the warmest zones.

If you start seeds indoors — which most home growers do — begin them six to eight weeks before your last frost date. This gives seedlings time to grow strong before transplanting. A seedling started indoors in early March can go outside in mid-May in a northern climate, or in early April in a southern one.

Key Takeaways

  • Plant tomatoes one to two weeks after your area's last frost date, when soil temperature reaches 60°F or warmer.
  • Start seeds indoors six to eight weeks before your last frost date if you want a head start on the growing season.
  • Transplant seedlings outdoors only after they have developed true leaves and the soil has warmed — cold soil causes rot and stunted growth.
  • In warm climates, you can plant a second crop in late summer for a fall harvest, as long as plants mature before the first frost.
  • Determinate (bush) varieties mature faster than indeterminate (vining) types, so choose based on how long your growing season lasts.

How to know your last frost date and soil temperature

The USDA Plant Hardiness Zone Map divides the country into zones based on average minimum winter temperatures. Your zone tells you roughly when frost stops, but the exact date varies year to year. The most reliable source is your local Cooperative Extension office, which publishes the average last frost date for your county. Search "[your county] Cooperative Extension" online or call your county's agricultural office.

To measure soil temperature, use a soil thermometer — a straightforward dial or digital probe that costs $10 to $20 and lasts for years. Push it 4 inches into the ground in the morning, in the spot where you plan to plant. Take the reading three days in a row. If it reads 60°F or higher on all three days, the soil is ready. If it dips below 60°F at night, wait another week and test again.

Do not rely on air temperature alone. A sunny day can feel warm while the soil stays cold, especially in spring. Tomatoes planted in soil below 55°F often develop root rot and never recover, even if the air warms later.

Starting seeds indoors versus buying transplants

Starting seeds indoors gives you more variety to choose from and costs less per plant, but requires grow lights, a shelf or stand, and attention to watering. Buying transplants from a nursery or garden center is faster and requires no equipment — you straightforward harden them off (expose them gradually to outdoor conditions over a week) and plant them out.

If you start seeds indoors, sow them in seed-starting mix under grow lights six to eight weeks before your last frost date. Keep soil moist but not waterlogged, and maintain temperatures between 70°F and 75°F. Once seedlings develop their first true leaves (the second set to appear), thin them so each plant has room to grow. Move them to larger pots as they grow.

Hardening off takes about a week. Place seedlings outdoors in a sheltered, shaded spot for an hour on day one, then gradually increase time and sun exposure each day. By day seven, they can handle full sun and outdoor conditions. Transplant them into the garden the day after hardening off is complete.

Planting depth and spacing for strong roots

Tomatoes have a useful trick: they can grow roots all along their buried stem. Plant seedlings deeper than they grew in their pots — bury the stem up to the first true leaves. This creates a stronger root system and helps the plant anchor itself as it grows tall. Remove the lowest leaves before burying; they would rot in the soil anyway.

Space plants 24 to 36 inches apart, depending on the variety. Determinate (bush) types stay compact and need less space; indeterminate (vining) types sprawl and need more room. Crowded plants develop disease because air cannot circulate around the leaves. If you are growing in containers, use a pot at least 5 gallons for determinate varieties and 10 gallons for indeterminate ones.

Add compost or aged manure to the planting hole. Tomatoes are heavy feeders and benefit from organic matter worked into the soil before planting. If your soil is poor, mix in a balanced fertilizer (such as 5-5-5 or 10-10-10) according to package directions, or use a tomato-specific fertilizer formulated for transplants.

Timing for determinate and indeterminate varieties

Determinate tomatoes (also called bush types) grow to a fixed size, flower all at once, and produce most of their fruit within a short window — usually four to six weeks. They mature faster, often in 60 to 75 days. These are ideal if you have a short growing season or want to harvest and preserve a large batch at once.

Indeterminate tomatoes (vining types) grow continuously throughout the season, flower and fruit over months, and keep producing until frost kills them. They take longer to mature — often 75 to 90 days to first fruit — but produce steadily from mid-summer through fall. Choose these if you want fresh tomatoes all season and have a long frost-free period.

Check the seed packet or plant label for days to maturity. Count backward from your first fall frost date (the average date of the first frost in autumn for your area) to see if the variety will finish before cold arrives. If your first frost is October 15 and a variety needs 85 days, plant it by July 22 at the latest. In short-season areas, stick with determinate or early-maturing varieties.

Summer planting for a fall crop in warm climates

In zones where the growing season is long — roughly the South and Southwest — you can plant a second crop of tomatoes in mid to late summer for a fall harvest. This works only if plants have time to mature before the first frost date. Count the days to maturity backward from your first frost date. If you have 90 days before frost and a variety needs 80 days, plant it by mid-July.

Summer-planted tomatoes face heat stress and need consistent water. Mulch heavily to keep soil cool and moist. Afternoon shade helps in extreme heat. Watch for spider mites and other pests that thrive in hot, dry conditions. Many growers in warm climates prefer to plant in late winter or early spring instead, when conditions are milder.

Protecting seedlings from late frost

Even after you plant, a surprise frost can kill young tomatoes. If frost is forecast within a week of planting, cover plants with row covers, blankets, or cloches (bottomless plastic jugs work). Remove the cover during the day so plants get sun and air. Keep covers on at night until the frost risk passes.

If plants are already in the ground and frost hits, water them thoroughly before the cold arrives. Moist soil holds heat better than dry soil. After frost, do not remove damaged leaves right away — wait a few days to see if the plant recovers. Many tomatoes bounce back from light frost damage.

Frequently Asked Questions

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

Yes, row covers can protect young plants from frost, but the soil still needs to be warm enough. If soil temperature is below 60°F, the plant will not grow even under a cover. Plant when soil is warm, then use covers if frost threatens after planting.

What if I plant tomatoes too early and they get stunted?

Stunted plants from cold soil often never fully recover. If you notice slow growth and yellowing leaves weeks after planting, the damage is usually done. For next year, wait for warmer soil. If it happens mid-season, pull the plant and replant with a new transplant if you have time before your first frost.

How long can I wait after my last frost date to plant?

You can plant anytime after your last frost date, but planting within two weeks gives you the longest growing season. Planting in June or July is fine in warm climates, but in northern areas it may not give plants enough time to mature before fall frost arrives.

Do I need to harden off seeds I started indoors?

Yes. Seedlings grown indoors under lights are tender and will wilt or die if moved directly to outdoor sun and wind. Harden them off over seven to ten days by gradually increasing their time outside and sun exposure. This toughens the leaves and stems.

Can I plant tomatoes in containers on a different schedule?

Container soil warms faster than ground soil, so you can plant a week or two earlier. However, containers dry out quickly in heat, so you will water more often. The timing rules for frost and soil temperature still explore — do not plant in cold soil, even in a pot.