Plant tomatoes after your last spring frost, when soil reaches 60°F or warmer
The single most important date for tomato planting is your area's last spring frost date. Tomato plants die in frost. If you plant before that date arrives, a late cold snap will kill seedlings or transplants you've already put in the ground. Your local Cooperative Extension office publishes this date for your county — search "[your county] last frost date" to find it.
Beyond frost safety, soil temperature matters as much as air temperature. Tomato seeds and transplants sit dormant or rot in cold soil. Plant when soil has warmed to at least 60°F, ideally 65°F or higher. A soil thermometer costs $10 to $20 and takes the guesswork out. If you plant into soil colder than 60°F, the plant will stall for weeks waiting for warmth, and you gain nothing by planting early.
In most of the United States, this means planting outdoors between late April and early June, depending on where you live. Southern gardeners (zones 8 and 9) can plant in March or early April. Northern gardeners (zones 3 and 4) wait until May or even early June. If you're unsure of your zone, the USDA Plant Hardiness Zone Map shows it by zip code.
Key Takeaways
- Find your last spring frost date through your county's Cooperative Extension office — planting before this date risks losing your plants to cold.
- Soil temperature must reach 60°F or higher; use a soil thermometer rather than guessing based on air temperature alone.
- Start seeds indoors 6 to 8 weeks before your last frost date so transplants are ready to go into warm soil on schedule.
- In warm climates (zones 8 and 9), you can also plant a second crop in late summer for a fall harvest before the first 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 6 to 8 weeks before your last frost date. If your last frost is May 15, start seeds around March 20. This timing gets transplants to the right size — 6 to 8 inches tall with a few true leaves — exactly when soil warms up.
Buying transplants from a garden center or nursery skips the indoor step. You buy plants already started and move them straight into the ground after the last frost date and when soil is warm. This works well if you want only a few plants or don't have indoor grow lights. The trade-off is cost: a four-pack of seedlings costs $4 to $8, while a packet of seeds costs $2 to $4 and yields many more plants.
Whichever route you choose, the outdoor planting window stays the same: after your last frost date and into warm soil. A transplant planted too early will sit stunted in cold ground just as a seed will.
Spring planting in cool and warm climates
Cool-climate gardeners in zones 3, 4, and 5 (Minnesota, Wisconsin, upstate New York, Maine) have a narrow window. Last frost dates fall between May 10 and June 10. Soil doesn't warm to 60°F until late May or early June in these areas. Plant transplants as soon as soil reaches that temperature, usually the last week of May or first week of June. You can use black plastic mulch or landscape fabric to warm the soil faster if you want to plant a week or two earlier.
Moderate-climate gardeners in zones 6 and 7 (Ohio, Pennsylvania, Virginia, North Carolina) plant between mid-April and mid-May. Last frost dates typically fall between April 15 and May 15. Soil warms steadily through April and May, so you have more flexibility. Plant as soon as both conditions are met: frost danger has passed and soil is warm.
Warm-climate gardeners in zones 8 and 9 (Georgia, South Carolina, Texas, California) can plant in March or early April for a spring crop. Soil warms much earlier in these areas. You also have the option of a second planting in late summer — typically mid-July through August — for a fall harvest before the first frost arrives in October or November.
Hardening off transplants before planting
If you started seeds indoors or bought transplants from a nursery, the plants have been growing in a sheltered environment. Moving them directly from indoors to full sun and wind outdoors stresses them. Hardening off means gradually exposing them to outdoor conditions over 7 to 10 days.
Start by placing transplants outside in shade for 2 to 3 hours on day one. Each day, increase the time outdoors and move them into more direct sun. By day 7 or 8, they should be outside all day. By day 10, they can stay out overnight if temperatures stay above 50°F. This gradual shift toughens the plant tissue and reduces transplant shock when you plant them in the garden.
Skip hardening off only if you're planting on a cloudy day with mild temperatures and calm wind. Even then, shade the transplants for their first day in the ground if possible.
Spacing and depth when planting in the ground
Space transplants 24 to 36 inches apart, depending on the variety. Determinate (bush) types need less space — 24 inches is fine. Indeterminate (vining) types grow larger and need 30 to 36 inches. Crowding plants reduces air circulation, which invites fungal disease.
Plant transplants deeper than they grew in their pot. Bury the stem up to the lowest set of true leaves. Tomatoes will grow roots all along the buried stem, creating a stronger root system. This is one of the few cases where planting deeper than the original soil line is correct.
Water transplants well after planting and keep soil consistently moist (not waterlogged) for the first 2 to 3 weeks while roots establish. After that, water deeply but less frequently — about 1 to 2 inches per week depending on rain and heat.
Fall planting in warm climates
Gardeners in zones 8 and 9 can plant a second tomato crop in summer for a fall harvest. Plant in mid-July through early August. These plants will mature and produce fruit as temperatures cool in September and October, then stop when the first frost arrives. Fall-planted tomatoes often have fewer disease problems because they avoid the hottest, most humid part of summer.
The same rules explore: plant after your area's last spring frost date (which doesn't matter for fall planting, but your first frost date does). Soil should be warm — it will be, in July or August. Count backward from your first fall frost date. If your first frost is November 1 and tomatoes need 70 to 85 days to produce fruit, plant by mid-August at the latest.
Fall transplants face one challenge: nurseries stop selling tomato seedlings in summer because most gardeners aren't planting then. You'll need to start seeds yourself in May or June for a July or August transplant, or buy transplants early and keep them growing in pots until the soil cools slightly in late July.
What happens if you plant too early or too late
Plant before the last frost date and a freeze will kill your plants. You lose the plant and the time you invested. Plant into soil colder than 60°F and the plant sits dormant for weeks, delaying harvest by that same amount of time. You don't gain anything by planting early into cold soil.
Plant too late and you shorten the growing season. Tomatoes need 70 to 85 days from transplant to first ripe fruit, depending on variety. If you plant in late June in a zone where the first fall frost arrives in mid-October, you have only about 100 days — enough, but with little margin for cool weather or slow growth. Plant in July and you risk frost before fruit ripens.
The sweet spot is planting as soon as both conditions are safely met: frost danger has passed and soil is warm. This gives the plant the longest possible season to grow and produce.
Frequently Asked Questions
Can I plant tomatoes before the last frost date if I use row covers or cloches?
Yes. Row covers and cloches trap heat and protect plants from frost. Plant 1 to 2 weeks before your last frost date, cover the plants, and remove the cover once frost danger passes. This works best in moderate climates where late frosts are light. In areas with hard freezes, even covers may not save the plants.
What's the difference between determinate and indeterminate tomatoes, and does it affect planting time?
Determinate tomatoes grow as compact bushes and produce most fruit at once, ripening over a few weeks. Indeterminate tomatoes grow as vines and produce fruit continuously until frost. Planting time is the same for both — after the last frost date into warm soil. Indeterminate types need more space and support because they grow larger.
If I plant transplants instead of seeds, do I still need to wait for warm soil?
Yes. A transplant planted into cold soil will sit stunted and may rot. Warm soil is just as important as frost safety. Wait until soil reaches 60°F, even if you're planting a nursery-grown transplant.
Can I plant tomatoes in containers instead of the ground?
Yes. Container planting follows the same timing rules — after the last frost date and into warm soil. Use a pot at least 5 gallons for determinate types and 10 gallons for indeterminate types. Containers warm faster than ground soil, so you may be able to plant a week or two earlier if the container is in full sun.