The Right Time to Plant Tomatoes Depends on Your Location and Season

You can plant tomatoes outdoors once the soil temperature reaches 60°F and the danger of frost has passed. In most of the United States, this happens between late April and early June, depending on where you live. Tomatoes grow best when nighttime temperatures stay above 50°F consistently — planting too early into cold soil will stunt them or cause the seeds to rot.

If you are starting from seed indoors, begin 6 to 8 weeks before your last spring frost date. If you are buying seedlings from a nursery, you can plant them directly into the garden once outdoor conditions warm up. The timing matters more than the calendar date — a tomato planted into 55°F soil in May will sit dormant longer than one planted into 70°F soil in late May.

Key Takeaways

  • Soil temperature must reach at least 60°F before planting tomatoes outdoors; 70°F or warmer is ideal for faster growth.
  • Your last spring frost date determines when it is safe to move seedlings outside; frost will kill young plants.
  • Starting seeds indoors 6 to 8 weeks before your last frost date gives you larger plants ready to transplant.
  • Nighttime temperatures below 50°F will slow growth and stress plants even if daytime warmth seems adequate.
  • Nursery seedlings can go in the ground as soon as conditions warm, but hardening them off first (gradual exposure to outdoor conditions) prevents transplant shock.

Finding Your Last Spring Frost Date

Your last spring frost date is the average date of the final frost in your area. This is the single most important number for timing tomato planting. You can find it by entering your zip code into the USDA Plant Hardiness Zone map at planthardiness.ars.usda.gov, or by searching "[your city] last frost date" online.

Frost dates vary by 2 to 4 weeks depending on elevation, proximity to water, and local geography. A town 20 miles north of you may have a frost date 10 days later. If you are unsure, ask at a local garden center or your county extension office — they know the actual conditions in your area better than a national map.

Soil Temperature Matters More Than Air Temperature

A warm day in April does not mean the soil is warm enough. Soil warms more slowly than air, especially if it is still wet from spring rain. Tomatoes planted into cold, wet soil will sit there doing nothing for weeks, and the seeds or roots may rot before they germinate or establish.

You can check soil temperature with an inexpensive soil thermometer (available at any garden center for $5 to $15). Push it 4 inches into the ground in the morning. If it reads 60°F or higher, you are ready to plant. If you do not have a thermometer, wait until nighttime temperatures stay above 50°F for a week — that is a reliable sign the soil has warmed enough.

Hardening Off Seedlings Before Planting

Seedlings started indoors or bought from a nursery have been in a sheltered environment. Moving them directly into full sun and wind will stress or kill them. Hardening off means gradually exposing them to outdoor conditions over 7 to 10 days before planting.

Start by placing seedlings in a shaded, sheltered spot outdoors for 2 to 3 hours. Each day, increase the time outside and move them into more sun. By day 7 or 8, they should be in full sun for the whole day. After 10 days, they are ready to plant in the garden. This process toughens the plants and prevents the wilting and leaf damage that comes from sudden exposure to outdoor stress.

Planting Depth and Spacing

Bury tomato seedlings deeper than they were growing in their pots — up to the first true leaves. Tomatoes will grow roots all along the buried stem, creating a stronger root system. This is one of the few plants where burying it deeper actually helps.

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. Crowded plants are more prone to disease because moisture sits on the leaves. If you are planting in containers, use a pot at least 5 gallons for a full-size plant, or 2 to 3 gallons for a dwarf variety.

What to Do If Frost Is Forecast After Planting

If you have already planted and frost is predicted, cover plants with blankets, sheets, or frost cloth in the evening. Remove the cover the next morning once temperatures rise above freezing. A single frost event after planting can kill young plants, so it is worth the effort to protect them.

If frost damage does occur, do not pull the plants out when ready. Wait a few days to see if they recover. Tomatoes are tougher than they look, and light frost damage to the leaves may not kill the plant. If the stem is blackened or mushy, the plant is dead and should be removed.

Growing Tomatoes in Containers and Indoors

Container tomatoes follow the same rules as in-ground plants: soil temperature and frost danger matter just as much. A pot sitting on cold ground will stay cold longer than in-ground soil, so wait until conditions are warm before moving containers outside. You can start containers indoors under grow lights and move them outside once nighttime temperatures stay above 50°F.

If you live in a short-season area or want to extend the growing period, start seeds indoors under lights 8 to 10 weeks before your last frost date. Keep seedlings under lights 14 to 16 hours per day, positioned 2 to 3 inches above the plants. Once they develop true leaves (the second set of leaves that appear), thin them or transplant them into individual pots to prevent crowding.

Frequently Asked Questions

Can I plant tomatoes in early spring if I use black plastic or row covers to warm the soil?

Yes. Black plastic laid over the soil for 2 to 3 weeks before planting will raise soil temperature by 5 to 10 degrees. Row covers or cloches placed over young plants after planting provide frost protection and keep soil warm. Remove covers once nighttime temperatures stay consistently above 50°F to prevent overheating.

What happens if I plant tomatoes too early?

Cold soil slows root development and seed germination. The plant may sit dormant for weeks without growing, or the roots may rot before they establish. Even if the plant survives, early planting rarely produces fruit faster than waiting for warm soil — the delayed growth usually cancels out any head start.

Is it too late to plant tomatoes in summer?

It depends on your location and how long your growing season lasts. In most areas, tomatoes need 60 to 85 days from transplant to first fruit, depending on variety. If your first fall frost arrives before that window closes, late plantings will not produce much. Check your frost date and count backward to see if you have time.

Can I plant tomatoes in fall instead of spring?

In warm climates (zones 9 and warmer), fall planting works well because plants grow through the mild winter and produce in spring. In cooler areas, fall-planted tomatoes will not mature before frost. If you live in a cold climate, spring is your only option.

Do I need to wait for the soil to dry out before planting?

Wet soil is harder to work with and stays cold longer, but you do not need to wait for it to be bone-dry. If the soil is muddy or compacted, wait a few days. If it crumbles in your hand, it is ready. Planting into overly wet soil can cause root rot, so err on the side of waiting if you are unsure.