Plant tomatoes after your last spring frost date, when soil reaches 60°F and ideally stays above 50°F at night

The single most important date for tomato planting is your local last frost date — the average day when freezing temperatures stop for the season. Tomatoes die in frost. Plant too early and a late freeze will kill seedlings or transplants overnight. Plant at the right time and you avoid replanting, disease pressure, and wasted weeks.

Find your last frost date by entering your zip code into the USDA Hardiness Zone map or asking your local cooperative extension office. Once you know that date, wait until it has passed, then wait another week or two. Soil temperature matters as much as air temperature. Tomato roots stop growing below 60°F and rot easily in cold, wet soil. A soil thermometer costs $10 to $20 and tells you when the ground is actually ready, not just the calendar.

In most of the United States, this means planting between mid-April and late May. In the Deep South and parts of the Southwest, it can be as early as late February or March. In the far North, it may not be safe until June. The timing also depends on whether you are planting seeds directly into the ground or transplanting seedlings you started indoors.

Key Takeaways

  • Your last frost date is the cutoff — tomatoes planted before it will likely freeze and die, so check your local date before buying plants.
  • Soil temperature of at least 60°F matters more than air temperature, and a $15 soil thermometer removes the guesswork.
  • Direct seeding into the ground takes longer to produce fruit than transplanting seedlings, so choose your method before deciding when to plant.
  • In warm climates, you may plant tomatoes twice a year — once in spring and again in late summer for a fall harvest.
  • Hardening off transplants by exposing them to outdoor conditions for a week before planting prevents shock and sunscald.

Planting from seed directly in the ground

Direct seeding means putting tomato seeds straight into garden soil outdoors. This works best in regions with a long growing season — roughly 80 days or more between your last frost and first fall frost. Seeds germinate in 5 to 10 days if soil is warm (70°F to 80°F), but take 3 to 4 weeks in cooler soil. Seedlings are fragile and slow to establish.

Plant seeds 1/4 inch deep, 2 to 3 inches apart, after your last frost date and once soil reaches 60°F. Thin seedlings to 24 to 36 inches apart once they have two true leaves. Direct-seeded tomatoes typically flower 60 to 80 days after planting, depending on variety. In zones with a short season, direct seeding often means no ripe fruit before the first fall frost.

The advantage is no transplant shock and lower cost. The disadvantage is a later harvest and higher failure rate from pests, disease, and weather. Most home gardeners in cooler climates skip direct seeding and start with transplants instead.

Planting transplants started indoors

Most gardeners buy seedlings from a nursery or start their own indoors 6 to 8 weeks before the last frost date. A seedling started indoors in late February in a cold climate will be ready to transplant outdoors in late April or early May, right around the frost date. This method gives you a head start: transplants flower 30 to 50 days after planting outdoors, so you harvest fruit 2 to 4 weeks earlier than direct-seeded plants.

Harden off transplants before planting them outside. Set them in a sheltered spot outdoors for 1 to 2 hours on day one, then gradually increase time and exposure to wind and sun over 7 to 10 days. Unhardened transplants sunburn, wilt, and often die when moved straight from a warm indoor shelf to full sun and wind. This step takes a week but prevents replanting.

Plant transplants after the last frost date, when soil is at least 60°F. Bury the stem up to the first true leaves — tomatoes root along the buried stem and develop a stronger root system. Space plants 24 to 36 inches apart depending on variety. Water well after planting and keep soil consistently moist (not soggy) for the first 2 to 3 weeks while roots establish.

Regional timing differences

Last frost dates vary by hundreds of miles and hundreds of days. In zone 3 (parts of Minnesota, Wisconsin, and upstate New York), the last frost date is around May 20 to June 10. In zone 5 (southern New England, Ohio, and parts of Colorado), it is April 20 to May 20. In zone 8 (parts of Texas, Georgia, and California), it is March 15 to April 15. In zone 9 and warmer, frost may not occur at all, or only rarely.

Warm-climate gardeners often plant tomatoes twice: once in early spring for a summer harvest, and again in late summer (July or August) for a fall harvest. The second planting avoids the hottest part of summer, when tomatoes stop setting fruit above 90°F. Cool-climate gardeners get one window in spring and must choose varieties that mature in 60 to 75 days to finish before the first fall frost (usually September 15 to October 15).

Check your local cooperative extension website for your exact frost dates and recommended planting windows. They also list tomato varieties that perform well in your region — some are bred for short seasons, others for heat tolerance or disease resistance.

Soil preparation before planting

Tomatoes need well-draining soil rich in organic matter. Before planting, work 2 to 3 inches of compost or aged manure into the top 8 to 10 inches of soil. This improves drainage, adds nutrients, and helps soil retain moisture without becoming waterlogged. Tomatoes prefer a soil pH between 6.0 and 6.8; if your soil is very acidic or alkaline, a soil test from your extension office will tell you how much lime or sulfur to add.

If you are planting in containers, use a quality potting mix (not garden soil), which drains faster and resists compaction. A 5-gallon container is the minimum for a determinate variety; indeterminate types need 10 gallons or more. Container soil dries faster than ground soil, so you will water more often.

Avoid planting tomatoes in the same spot year after year. Rotate to a different bed every 3 to 4 years to reduce soil-borne diseases like early blight and fusarium wilt. If you must replant in the same location, remove the top 6 inches of soil and replace it with fresh compost.

Protecting young plants from late frost

Even after your last frost date, a surprise cold snap can occur. If frost is forecast within a week of planting, cover transplants with row covers, cloches, or even overturned buckets on the coldest nights. Remove covers during the day so plants get light and air. This protection buys you a few degrees and can save a crop.

If a frost does kill your transplants, do not replant when ready. Wait a week or two for soil to warm again, and choose a different location if possible to avoid replanting in cold soil. Some gardeners keep extra seedlings indoors as backup for exactly this reason.

Frequently Asked Questions

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

Row covers provide 2 to 4 degrees of frost protection, which may not be enough if temperatures drop to 28°F or below. It is safer to wait until after the last frost date and use covers only for unexpected late frosts. Planting too early in cold soil also slows root growth and increases disease risk.

What if my soil is still cold but the calendar says I can plant?

Use a soil thermometer. If soil is below 60°F, wait another week or two. A cold soil will rot roots and stunt growth more than a late planting will. Warm soil matters more than the calendar date.

Can I plant tomatoes in summer instead of spring?

In warm climates (zones 8 and warmer), yes — plant in late July or August for a fall harvest. In cooler climates, a summer planting will not mature before frost. Check your first fall frost date and count backward 70 to 85 days to find the latest safe planting date for your region.

Do I need to wait a full week after hardening off before planting?

Hardening off usually takes 7 to 10 days. You can plant as soon as the process is done and soil is warm enough. Rushing it — planting after only 2 or 3 days of outdoor exposure — often results in wilted or sunburned plants that take weeks to recover.

What happens if I plant tomatoes too close together?

Crowded plants compete for water, nutrients, and light. They also have poor air circulation, which increases fungal disease like early blight and powdery mildew. Space plants 24 to 36 inches apart depending on variety. Check the seed packet or plant label for the recommended spacing.