Plant tomatoes after your last frost date, when soil temperature reaches at least 60°F (ideally 65–70°F)

The single most important rule for tomato timing is this: tomatoes are killed by frost. A single night below 32°F will destroy seedlings or transplants. Your last frost date is the average date of the final frost in spring for your location — find it by entering your zip code at almanac.com/gardening/frostdates or asking your local cooperative extension office.

Plant transplants (the small plants you buy or grow indoors) outdoors 1 to 2 weeks after that date, once nighttime temperatures stay above 50°F. Direct-seeding (planting seeds straight in the ground) happens 2 to 3 weeks after your last frost date, when soil has warmed further. Cold soil slows germination and invites rot; warm soil wakes seeds up.

Check soil temperature with a soil thermometer pushed 4 inches deep. If you do not have one, wait until daytime air temperature has been consistently above 70°F for at least a week — that usually means soil is warm enough. Planting too early is the most common mistake; the plant will sit there sulking instead of growing.

Key Takeaways

  • Tomatoes cannot survive frost, so wait until 1 to 2 weeks after your area's last frost date before planting transplants outdoors.
  • Soil temperature matters more than air temperature — aim for at least 60°F, ideally 65–70°F, measured 4 inches deep.
  • Direct-seeding (planting seeds) happens 2 to 3 weeks after your last frost date, when soil is warmer than transplanting time.
  • Nighttime temperatures should stay above 50°F consistently before you move seedlings outside, or they will stall and may rot.
  • Starting seeds indoors 6 to 8 weeks before your last frost date gives you larger transplants ready to go into the ground on time.

Finding your last frost date and first frost date

Your last frost date tells you when spring frost stops; your first frost date tells you when fall frost begins. Together they define your growing season — the window when tomatoes can live outdoors. Both dates vary by location, elevation, and even neighborhood microclimates.

The fastest way to find both dates is the USDA Hardiness Zone Map (planthardiness.ars.usda.gov). Enter your zip code and you will see your zone. Then search "[your zone] last frost date" — most zones have a standard date published by the National Weather Service or your state's agricultural extension.

Your local cooperative extension office (search "[your county] cooperative extension") has the most accurate dates for your specific area and can tell you about typical spring and fall weather patterns. They also know which tomato varieties grow best in your climate.

Starting seeds indoors versus buying transplants

Starting seeds indoors 6 to 8 weeks before your last frost date gives you control over timing and variety choice. Seeds need warmth (70–75°F), light (14 to 16 hours daily under grow lights), and consistent moisture. Seedlings are ready to move outdoors when they have 2 to 3 sets of true leaves (the leaves that look like tomato leaves, not the first round of oval seed leaves).

Buying transplants from a nursery or garden center is faster and requires no indoor setup. Choose stocky, dark-green plants with no flowers yet — flowering transplants are stressed and will take longer to recover after planting. Avoid tall, pale, spindly plants; they were started too early or kept in poor light.

Whichever route you choose, harden off your seedlings 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 direct sun over 7 to 10 days. This toughens the plant and prevents transplant shock.

Soil temperature and nighttime air temperature

Cold soil is the silent killer of early-planted tomatoes. A transplant in 50°F soil will sit motionless for weeks, using energy to survive rather than grow. Worse, cool, wet soil invites damping-off disease and root rot. Warm soil (65–70°F) triggers root growth and fast establishment.

Measure soil temperature at 4 inches deep with a soil thermometer, ideally in the morning before the sun warms the surface. If you do not have a thermometer, use this rule: when daytime air temperature has been above 70°F for 7 to 10 consecutive days, soil is usually warm enough. In most regions, this happens 1 to 2 weeks after your last frost date.

Nighttime temperature matters just as much. Tomato transplants slow their growth when nights drop below 55°F and stop growing entirely below 50°F. If a cold snap is forecast after planting, cover plants with row covers or cloches (clear plastic domes) to trap heat. Remove covers once temperatures rise.

Timing for determinate versus indeterminate varieties

Determinate tomatoes (bush types like Roma and San Marzano) grow to a fixed size, flower all at once, and produce most of their fruit in a short window — usually 4 to 6 weeks. Indeterminate tomatoes (vining types like Brandywine and Cherokee Purple) grow continuously, flower throughout the season, and produce fruit until frost kills the plant.

This matters for timing because determinate varieties need to mature before your first fall frost, but they are more forgiving of late planting. Indeterminate varieties benefit from early planting because they have all summer and fall to produce. If your growing season is short (fewer than 100 frost-free days), choose determinate or early-maturing varieties and plant as soon as soil warms.

Check the seed packet or plant label for "days to maturity" — this is the number of days from transplanting to first ripe fruit. Add 2 to 3 weeks to account for slower growth in cool spring weather. If days to maturity plus 2 to 3 weeks exceeds the number of days between your last and first frost dates, the variety will not ripen in your climate.

Extending the season with row covers and walls of water

If you want to plant earlier than soil temperature allows, use a row cover (lightweight fabric that lets light and water through) or a wall of water (a circle of water-filled tubes that radiates heat). Both trap warmth and protect plants from frost. Row covers can raise soil temperature by 2 to 4°F; walls of water can raise it by 8 to 15°F.

Plant through the row cover or wall of water, then leave it in place until nighttime temperatures stay above 50°F. Remove it gradually over a few days so the plant adjusts to outdoor conditions. This method lets you plant 2 to 3 weeks earlier than normal, giving you a longer harvest window — especially valuable in short-season climates.

Walls of water are more effective but bulkier and more expensive. Row covers are cheaper and easier to store. Both work best in raised beds or containers where you can control soil temperature more easily than in-ground gardens.

Planting in containers versus in-ground beds

Container soil warms faster than in-ground soil because it is exposed to air on all sides. This means you can plant in containers 1 to 2 weeks earlier than in-ground gardens in the same location. Use containers at least 5 gallons (for determinate varieties) or 10 gallons (for indeterminate varieties), filled with potting mix, not garden soil.

In-ground beds warm more slowly but retain moisture better and give roots more room to spread. Raised beds warm faster than ground-level beds because they are elevated and exposed to more sun. If you have a choice, plant in raised beds or containers for earlier harvests.

Regardless of container or bed type, mulch the soil surface with 2 to 3 inches of straw or wood chips once soil warms. Mulch keeps soil temperature stable, reduces watering needs, and prevents soil-borne diseases from splashing onto leaves.

Frequently Asked Questions

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

You will need to replant. Save time by buying new transplants rather than starting seeds again — you are already past the seed-starting window. Plant the new transplants and use row covers or walls of water to protect them. Most gardeners who lose plants to early frost plant again within a week and still harvest a full crop.

Can I plant tomatoes in summer for a fall crop?

Yes, but only if your first frost date is at least 60 to 70 days away. Count backward from your first frost date and subtract the variety's days to maturity plus 2 to 3 weeks for slower growth in cooling weather. If the math works, buy transplants (not seeds — there is no time to start them) and plant in mid to late summer. Fall tomatoes often taste better because nights are cooler.

Does it matter what time of day I plant tomatoes?

Plant in late afternoon or on a cloudy day to reduce transplant shock. Avoid planting in full sun at midday — the plant will wilt and may not recover. Water thoroughly after planting and keep soil moist for the first week while roots establish.

What if my area has unpredictable spring weather?

Wait until nighttime temperatures have been above 50°F for at least 10 consecutive days, even if your last frost date has passed. Unpredictable weather means a late frost is still possible. Use row covers as insurance — they are cheap and straightforward to deploy if frost is forecast.

How deep should I plant tomato transplants?

Bury the stem up to the lowest set of leaves. Tomatoes will root along the buried stem, creating a stronger root system. This is one of the few times deeper planting is better — it anchors the plant and improves drought tolerance.