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

The single most important date for tomato planting is your last spring frost date — the average date of the final frost in your area. Tomatoes cannot survive frost. Plant them too early and a late freeze will kill seedlings or transplants. Plant them too late and you lose weeks of growing season when temperatures are warm enough for fruit to ripen.

You can find your last frost date by entering your zip code into the USDA Hardiness Zone Map at planthardiness.ars.usda.gov, or by searching "[your city] last frost date" online. Most local extension offices and garden centers also have this information posted.

Beyond the frost date, soil temperature matters as much as air temperature. Tomato seeds germinate slowly in cold soil and may rot before sprouting. Transplants planted in soil below 60°F will sit dormant and stressed. Wait until soil reaches at least 60°F — ideally 65°F or warmer — before planting, even if your frost date has passed.

Key Takeaways

  • Never plant tomatoes before your last spring frost date; a freeze will kill them even if they have already sprouted.
  • Soil temperature must reach 60°F or higher before planting seeds or transplants, which usually happens one to two weeks after the last frost date.
  • In warm climates (zones 9 and above), you can plant tomatoes in late winter or early spring, or again in midsummer for a fall harvest.
  • Starting seeds indoors six to eight weeks before your frost date gives you larger transplants ready to go into the ground on planting day.
  • Tomatoes need 60 to 85 days from transplant to first ripe fruit, depending on variety, so count backward from your first fall frost to know your important date.

Planting dates by U.S. region

Northeast and upper Midwest (zones 4–5): Last frost dates fall between May 1 and May 31. Plant transplants outdoors in mid-to-late May. Soil warms slowly in these regions, so waiting until late May is safer than planting at the frost date itself. Start seeds indoors in late March or early April.

Mid-Atlantic and lower Midwest (zones 6–7): Last frost dates range from April 15 to May 15. Plant transplants in late April or early May. Soil temperature is the limiting factor here — air may warm quickly, but soil lags behind. Check soil temperature before planting.

Southeast (zones 8–9): Last frost dates fall between March 15 and April 15. You can plant transplants in mid-to-late April. Many gardeners in zone 9 also plant a second crop in late July or early August for a fall harvest, since tomatoes can tolerate heat better than cold.

Southwest and California (zones 9–10): Last frost dates are early — often February or March. Plant transplants in March or April for a spring harvest. In late summer (July or August), plant again for a fall and early winter harvest. Avoid planting in the hottest part of summer (June–July in most of the Southwest), as extreme heat stops fruit set.

Starting seeds indoors versus buying transplants

Starting seeds indoors gives you more variety choices and costs less per plant, but requires grow lights, heat mats, and space. Sow seeds six to eight weeks before your last frost date in seed-starting mix kept at 70–75°F. Seedlings need 14 to 16 hours of light daily from a grow light positioned 2 to 3 inches above the leaves. Thin seedlings to one per cell once they have their first true leaves.

Buying transplants from a garden center or nursery is faster and requires no equipment. Choose stocky plants with green leaves and no flowers yet — plants already flowering are often root-bound and stressed. Harden off transplants by setting them outside in a sheltered spot for a few hours each day for one week before planting, gradually increasing sun exposure. This toughens them to outdoor conditions.

Whether you start seeds or buy transplants, plant them outdoors only after the last frost date has passed and soil temperature is at least 60°F.

Soil temperature and how to measure it

A soil thermometer is the most reliable way to check soil temperature. Push it 4 inches into the soil in the morning, wait 30 seconds, and read the temperature. Tomatoes germinate and grow best when soil is 65–75°F. At 60°F, growth is slow but acceptable. Below 60°F, seeds rot and transplants stall.

Soil warms gradually after the last frost date. In most regions, soil reaches 60°F about one to two weeks after the average last frost date. In cool, wet springs, it may take longer. In sandy soil with good drainage, it warms faster than in clay soil. If you plant before soil is ready, your tomatoes will sit in the ground for weeks without growing, wasting time you need for fruit production.

Counting backward from your first fall frost date

Tomatoes need time to produce ripe fruit before the first fall frost. Most varieties take 60 to 85 days from transplant to first ripe fruit. Determinate (bush) varieties are usually faster, around 60 to 70 days. Indeterminate (vining) varieties often take 75 to 85 days or longer.

Find your first fall frost date the same way you found your spring date — through the USDA map or a local extension office. Count backward 70 to 85 days (depending on your variety) to find your latest safe planting date. For example, if your first fall frost is October 15 and your variety takes 75 days, plant by August 1 at the latest. Planting after that date means fruit will still be green when frost arrives.

This calculation is especially important in short-season regions (zones 4–5) and in the upper South, where the growing season is compressed. In warm climates with long seasons, you have more flexibility.

Hardening off and transplanting outdoors

Transplants grown indoors or bought from a nursery are soft and tender. Moving them directly from a sheltered environment to full sun and wind will shock them. Harden off by setting plants outside in a shaded, sheltered spot for 2 to 3 hours on day one. Each day, increase sun exposure and time outdoors by an hour or two, and reduce shelter from wind. By day 7 or 8, they should tolerate full sun and outdoor conditions.

Plant transplants in the ground after hardening off is complete and soil temperature is stable at 60°F or higher. Dig a hole slightly deeper than the root ball, set the plant in, and firm soil around it. Water well. If your transplant is leggy (tall and thin), you can bury it deeper — tomatoes will root along the buried stem and develop a stronger root system.

Frequently Asked Questions

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

Row covers and cloches provide some frost protection, but they are not reliable for a hard freeze. If temperatures drop below 32°F, most covers will not save tender seedlings. It is safer to wait until after the last frost date and use covers only as a backup for unexpected late frosts.

What if my area has an unpredictable spring and I am not sure when the last frost is?

Use the USDA Hardiness Zone Map or contact your local cooperative extension office — they have historical frost data for your exact location. If you are still uncertain, plant a week or two after the official date to add a safety margin. The extra week of waiting is better than losing plants to frost.

Can I plant tomatoes in summer if I missed the spring window?

In zones 8 and warmer, yes — plant in late July or August for a fall harvest. In cooler zones, summer planting usually does not work because the first fall frost arrives before fruit ripens. Check your first fall frost date and count backward to see if you have enough time.

Does it matter if I plant on a cloudy day versus a sunny day?

Planting on a cloudy day or in late afternoon reduces transplant stress because the plant does not face intense sun when ready after being moved. Water well regardless of weather. If you must plant on a sunny day, shade the transplant for a few days with a shade cloth or by positioning it where it gets afternoon shade.

What happens if soil is too cold and I plant anyway?

Seeds will rot in the soil without germinating. Transplants will sit dormant, turn pale, and may develop root rot. You will waste weeks waiting for growth that never comes, and you may lose the plant entirely. It is always better to wait for soil to warm.