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

The single most important rule for tomato planting is this: wait until the danger of frost has passed and the soil has warmed. Tomatoes are warm-season plants. They will not germinate in cold soil, and a late frost will kill seedlings or transplants outright. In most of the United States, this means planting outdoors between mid-April and late May, but the exact date depends entirely on where you live.

Your local frost date is the key number. This is the average date of the last frost in spring for your area. You can find it by entering your zip code at the National Weather Service website or by calling your county extension office. Once you know that date, count backward: plant tomatoes two to three weeks after your last frost date, when soil temperature has climbed to at least 60°F (ideally 65°F or warmer).

Soil temperature matters more than air temperature. A warm day in April does not mean the soil is warm. Use a soil thermometer—they cost five to ten dollars—and check the temperature at the depth where you will plant (usually four to six inches down). If you plant too early into cold, wet soil, seeds rot and transplants sit dormant and sulk.

Key Takeaways

  • Plant tomatoes two to three weeks after your area's last spring frost date, when soil temperature reaches 60°F or higher.
  • You can start seeds indoors six to eight weeks before your last frost date, then move seedlings outside once soil has warmed.
  • In warm climates with mild winters, you can plant a fall crop in late summer for harvest before the first fall frost.
  • Transplants go in the ground faster than seeds but cost more; seeds are cheaper and give you more variety choices.
  • A soil thermometer is the most reliable way to know if the ground is warm enough, regardless of what the air temperature says.

Starting seeds indoors versus buying transplants

You have two paths: start from seed indoors, or buy transplants (seedlings) from a nursery and plant them directly outside. Starting seeds indoors takes longer but costs less and gives you access to varieties you cannot find at a garden center. Buying transplants is faster and requires less equipment, but you pay more and your variety choices are limited to what the nursery stocks.

If you start seeds indoors, sow them six to eight weeks before your last frost date. Use seed-starting mix (not garden soil), keep it moist and warm (70–75°F), and provide bright light—a sunny windowsill works, but a grow light is more reliable. When seedlings have two true leaves, thin them or transplant them into individual pots. Harden them off (gradually expose them to outdoor conditions) for seven to ten days before planting outside.

If you buy transplants, choose stocky, dark-green plants with no flowers yet. Leggy, pale seedlings or those already in bloom are stressed and will take longer to recover. Plant them at the same depth they were growing in their pot, or even deeper—tomatoes can root along buried stems. Water well after planting.

Planting depth and spacing for transplants

Bury tomato transplants deeper than they grew in the nursery pot. Tomatoes develop roots all along their buried stem, which strengthens the plant and helps it access water and nutrients deeper in the soil. You can bury them up to the first true leaves if the plant is tall and leggy.

Space plants 24 to 36 inches apart, depending on the variety. Determinate (bush) types can be closer; indeterminate (vining) types need more room for air circulation. Good air flow reduces disease. If you are planting in rows, space rows 36 to 48 inches apart so you can walk between them and reach plants for pruning and harvesting.

Fall planting in warm climates

If you live in a warm climate—USDA zones 8 and warmer—you can plant a second tomato crop in late summer for fall and early winter harvest. Count backward from your first fall frost date. Plant in late July or August so plants mature before frost arrives. Fall-planted tomatoes often produce better fruit because temperatures are cooler and more stable than in summer heat.

Fall planting requires the same soil temperature rule: soil must be at least 60°F. In late summer, this is usually not a problem. Water more frequently in fall because plants are establishing roots in drying soil. Mulch heavily to keep soil cool and retain moisture.

Hardening off seedlings before planting

Seedlings started indoors are tender. They have never felt wind, direct sun, or temperature swings. If you move them straight from a warm, sheltered windowsill to the garden, they will wilt, bleach, or die. Hardening off means gradually exposing them to outdoor conditions over seven to ten days.

Start by placing seedlings in a shaded, sheltered spot outdoors for an hour or two. Each day, increase the time outside and gradually move them into more sun and wind. By day seven or ten, they should be able to spend the full day and night outside. Then plant them in the garden. This process toughens the stems and leaves and prepares the plant for the shock of transplanting.

Soil preparation before planting

Tomatoes are heavy feeders. They need rich, well-draining soil with plenty of organic matter. Before planting, work two to three inches of compost or aged manure into the top six to eight inches of soil. This improves drainage, adds nutrients, and feeds soil microbes.

If your soil is very acidic or alkaline, a soil test from your county extension office will tell you what to add. Tomatoes prefer soil with a pH between 6.0 and 6.8. If you are planting in containers, use potting mix, not garden soil—potting mix drains better and does not compact.

Protecting young plants from late frost

Even after you plant, a surprise late frost can damage or kill young tomato plants. If frost is forecast within a week of planting, cover plants with row covers, old sheets, or cloches (clear plastic domes). Leave the covers on until the frost passes and daytime temperatures stay above 50°F.

Another option is to wait to plant until soil is warmer and frost risk is lower. There is no prize for planting early. A tomato planted three weeks late into warm soil will catch up to and often outproduce one planted early into cold soil.

Frequently Asked Questions

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

You can, but it is usually not worth the effort. Row covers protect from frost but not from cold soil. Seeds will not germinate, and transplants will sit dormant and stressed. Wait until soil is warm, then plant without covers. The plant will grow faster and stronger.

What if my area's last frost date has already passed and I haven't planted yet?

Plant now if soil temperature is 60°F or warmer. Tomatoes planted in June will still produce a full crop; they just start later and finish later. You will harvest into fall instead of mid-summer, but the yield is usually the same.

Can I plant tomatoes in containers, and does the timing change?

Yes, containers work well. Timing does not change—wait until soil temperature is warm. Container soil warms faster than garden soil, so you may be able to plant a week or two earlier. Use a large pot (at least five gallons) and potting mix, not garden soil.

Is it better to plant seeds or transplants?

Transplants are faster and more reliable for most home gardeners. Seeds are cheaper and give you more variety. If you are new to gardening, start with transplants. Once you have experience, try seeds indoors to expand your options.

What happens if I plant tomatoes in soil that is too cold?

Seeds rot without germinating. Transplants sit stunted and pale, do not grow, and are vulnerable to disease. You waste time and money. Wait for warm soil—it is the single most important factor in tomato success.