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

The single most important rule: tomatoes go in the ground after the danger of frost has passed and the soil has warmed. Frost kills tomato plants outright. Cold soil (below 60°F) slows their growth so much that you lose weeks of production. Most gardeners plant tomatoes between mid-April and late May in cooler regions, and February through April in warm climates — but your local frost date is what matters, not the calendar.

You can find your area's last spring frost date through your county extension office or by searching "[your city] frost date" online. Once you know that date, wait at least one week after it before planting. Better yet, wait two weeks. Soil temperature matters more than air temperature — a warm day in early May can be followed by a cold snap that kills seedlings. A soil thermometer costs $10 and removes the guesswork.

Key Takeaways

  • Plant tomatoes one to two weeks after your area's last spring frost date, not before.
  • Soil temperature should be at least 60°F, ideally 65°F or warmer, before you transplant seedlings.
  • Starting seeds indoors six to eight weeks before your frost date gives you larger plants ready to go in the ground on time.
  • In hot climates, you can plant a second crop in late summer for a fall harvest, timing it so fruit matures before the first fall frost.

How to find your frost date and soil temperature

Your county extension office has your exact frost date — call them or visit their website. They also know the typical soil temperature for your area in each week of spring, which helps you decide whether to wait even after the frost date has passed. Many extension offices publish a planting calendar specific to your county.

If you want to measure soil temperature yourself, push a soil thermometer 4 inches into the ground in the spot where you plan to plant, early in the morning. Take the reading for three days in a row. If it averages 60°F or higher, you can plant. If it's still in the 50s, wait another week and test again. Soil warms fastest in raised beds and containers, so those can go in a week or two before in-ground beds.

Starting seeds indoors versus buying transplants

If you start tomato seeds indoors under grow lights, begin six to eight weeks before your frost date. Seeds germinate best at 70–75°F and need 14 to 16 hours of light per day. Seedlings are ready to transplant outdoors when they have their first true leaves (the second set of leaves that appear) and are 6 to 8 inches tall — usually right around your frost date.

Buying transplants from a nursery is simpler if you don't have grow lights or space. Look for stocky, dark green plants with no flowers yet. Leggy, pale seedlings or plants already in bloom will struggle in the garden. Harden off transplants by setting them outside in a sheltered spot for a few hours each day, gradually increasing exposure to sun and wind over a week. This toughens them before planting.

Planting depth and spacing matter for strong roots

Bury tomato seedlings deeper than they grew in their pots — up to the first true leaves. Tomatoes will sprout roots all along the buried stem, creating a stronger root system. This is one of the few times deeper planting actually helps. Space plants 24 to 36 inches apart, depending on the variety. Determinate (bush) types need less space; indeterminate (vining) types need more.

Water seedlings well after planting and keep soil consistently moist for the first two weeks while they establish roots. Mulch around the base with 2 to 3 inches of straw or shredded leaves, leaving a 2-inch gap around the stem to prevent rot. Mulch keeps soil temperature steady and reduces watering needs later.

Adjusting timing for your climate

In cool climates (zones 3–5), plant in late May or early June. Soil takes longer to warm, and late frosts are common. You can speed things up by laying black plastic over the bed for two weeks before planting — it absorbs heat and warms the soil faster.

In warm climates (zones 9–11), you have two planting windows. Spring planting happens earlier — often February or March — because heat arrives sooner. A second crop can go in during late summer, timed so plants mature and produce fruit before the first fall frost. Check your fall frost date the same way you checked your spring date, then count backward eight to ten weeks to find your late-summer planting window.

Common mistakes that delay harvest

Planting too early is the most common error. Even if daytime temperatures hit 70°F in April, a single frost night will kill seedlings or stunt them so badly that you lose a month of growth. The soil is still cold. Wait for consistent warmth — when nighttime lows stay above 50°F and soil reads 60°F or higher.

Planting in cold, wet soil invites root rot and fungal disease. If spring is unusually wet and cold, delay planting by a week or two rather than fighting the weather. A tomato planted in June in warm soil will often catch up to and surpass one planted in cold soil in May. Patience at planting time pays off in faster growth and healthier plants.

Frequently Asked Questions

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

Row covers and cloches protect seedlings from light frost, but they don't warm cold soil. If soil is still below 60°F, the plants won't grow much even under cover. Wait for soil to warm, then use covers only if an unexpected late frost is forecast.

What if I plant too early and frost kills my seedlings?

You'll need to replant. If you started seeds indoors, you may have backup seedlings. If you bought transplants, buy more and plant again once soil has warmed. This is why waiting for consistent warmth is worth the delay — replanting costs time and money.

How do I know if my soil is ready if I don't have a thermometer?

Touch the soil with your bare hand. If it feels cold and clammy, it's not ready. If it feels warm and crumbly, it's close. Your county extension office can also tell you the typical soil temperature for your area in each week of spring based on historical data.

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

Yes — containers warm faster than garden soil. You can plant in containers one to two weeks earlier than in-ground beds. Use a large pot (at least 5 gallons) filled with quality potting mix, which drains well and warms quickly.

What if I live somewhere with a very short growing season?

Choose early-maturing varieties that produce fruit in 60 to 70 days rather than 80 to 90 days. Start seeds indoors as early as possible (8 to 10 weeks before your frost date) to maximize the time plants have to grow and produce before fall frost arrives.