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

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 and will rot in cold soil or die if exposed to frost after planting. In most of the United States, this means planting between mid-April and late May, but the exact date depends entirely on where you live.

Your last spring frost date is the key number. This is the average date of the final frost in your area — after this date, freezing temperatures are unlikely. You can find your local frost date by searching "last frost date" plus your zip code, or by checking your county's cooperative extension office website. Once you know that date, wait one to two weeks after it before planting tomatoes directly in the ground.

Soil temperature matters as much as air temperature. Even if the air warms up in April, the soil may still be cold. Tomato seeds and seedlings planted in soil below 60°F will sit dormant and may rot before they grow. A soil thermometer (available at any garden center for under $15) takes the guesswork out — push it 4 inches into the ground in the morning and check the reading. When it consistently reads 60°F or above, you are ready to plant.

Key Takeaways

  • Plant tomatoes one to two weeks after your area's last spring frost date, when soil temperature is 60°F or warmer.
  • Starting seeds indoors six to eight weeks before your frost date gives you larger plants to transplant and a longer harvest season.
  • If you plant too early and frost threatens, cover seedlings with blankets or cloches the night before the freeze.
  • 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.

Starting seeds indoors versus buying transplants

You have two paths: start seeds indoors under lights, or buy seedlings from a nursery and transplant them. Starting seeds indoors takes more work but costs less and gives you more variety. Buying transplants is faster and requires no equipment, but limits you to what local nurseries stock.

If you start seeds indoors, begin six to eight weeks before your last frost date. Plant seeds in seed-starting mix in small pots or trays, keep them warm (70–75°F), and provide 14 to 16 hours of light daily under grow lights or on a sunny windowsill. When seedlings develop their first true leaves (the second set of leaves that appear), thin them so each pot holds one strong plant. Two weeks before your frost date, begin hardening off — moving seedlings outdoors for a few hours each day, gradually increasing time outside. This toughens them for transplanting.

Buying transplants from a nursery or garden center skips all of this. You straightforward choose healthy-looking plants with green leaves and no flowers yet, and transplant them into the garden after your frost date. Nursery transplants are usually ready to go into the ground when ready, though you should still harden them off for a few days if they have been indoors.

Timing for different tomato varieties

Determinate tomatoes (bush types that grow to a fixed size and produce most fruit at once) and indeterminate tomatoes (vining types that grow all season and produce continuously) both follow the same frost-date rule for planting. The difference shows up in harvest timing. Determinate varieties mature faster — usually 60 to 80 days from transplant — so they are good if you want a concentrated harvest for canning or sauce-making. Indeterminate varieties take 70 to 85 days to first fruit but keep producing until frost, so they are better for eating fresh all summer.

Cherry and heirloom tomatoes are almost always indeterminate, meaning they will grow tall and produce for months. Paste tomatoes (like San Marzano) are usually determinate. When you buy a seedling or seed packet, the label will say which type it is. This does not change when you plant — both types go in after your frost date — but it helps you choose varieties suited to what you want to do with the harvest.

Protecting early plantings from unexpected frost

Sometimes frost threatens after you have already planted. If the forecast calls for freezing temperatures within a week of planting, cover your seedlings. Use blankets, old sheets, cardboard boxes, or commercial frost cloth (row cover) — anything that traps heat and keeps frost from touching the leaves. Drape it loosely so it does not crush the plants, and remove it during the day once temperatures rise above freezing.

A simpler approach is to wait. If frost is forecast and your seedlings are not yet in the ground, delay planting by a week or two. Tomatoes are not harmed by waiting; they are harmed by cold soil and freezing air. There is no prize for planting earliest — there is only a harvest for planting at the right time.

Summer planting for a fall crop in warm climates

If you live in a warm climate where summers are hot and long, you can plant a second crop of tomatoes in late summer for a fall harvest. The timing works backward from your first fall frost date instead of your spring frost date. Count back 70 to 85 days (depending on variety) from your first fall frost, and that is when to plant seedlings for a fall crop.

This works best in zones 8 and warmer, where fall temperatures stay mild enough for tomatoes to ripen. In cooler zones, fall comes too fast and fruit will not mature before frost. Check your first fall frost date the same way you found your spring date — search online or contact your county extension office. If you have at least 70 days between mid-summer and the first frost, a fall crop is worth trying.

Spacing and soil preparation at planting time

Once soil temperature is right and frost danger has passed, prepare the planting spot. Tomatoes need full sun (at least six to eight hours daily) and well-draining soil rich in organic matter. Mix compost or aged manure into the top 8 to 10 inches of soil before planting. If your soil is heavy clay, add compost to improve drainage — tomatoes in waterlogged soil develop root rot and fungal diseases.

Space plants 24 to 36 inches apart (determinate varieties can be closer, indeterminate varieties need more room). Dig a hole slightly deeper than the root ball, and plant the seedling so the lowest leaves are just above soil level — tomatoes can develop roots along the buried stem, which strengthens the plant. Water thoroughly after planting, and mulch with 2 to 3 inches of straw or wood chips to keep soil temperature steady and reduce weeds.

Frequently Asked Questions

What if I plant tomatoes too early and they freeze?

Seedlings exposed to frost below 32°F will die. If frost threatens after planting, cover plants with blankets or row cover overnight. If seedlings freeze before you can cover them, they are lost — you will need to replant. This is why waiting until frost danger passes is safer than rushing.

Can I plant tomatoes in containers instead of the ground?

Yes. Container tomatoes follow the same frost-date rule — wait until after your last spring frost to plant. Use containers at least 5 gallons for determinate varieties and 10 gallons for indeterminate types. Containers warm faster than ground soil, so you may be able to plant a week or two earlier, but still check soil temperature first.

How do I know if my seedlings are ready to transplant?

Seedlings are ready when they are 6 to 8 inches tall, have several sets of true leaves, and have been hardened off (gradually exposed to outdoor conditions). They should look sturdy and green, not pale or leggy. If they are flowering already, they are slightly past ideal, but will still grow and produce.

What happens if soil is still cold when I plant?

Cold soil (below 60°F) slows growth and can cause seeds and seedlings to rot before they establish roots. The plant will sit dormant and may die. Wait for soil to warm — it only takes a week or two longer, and you will have healthier plants and a better harvest.