When to Plant Tomatoes

Plant tomatoes outdoors after the local danger of frost has passed and nights and soil are reliably warm. For many gardeners that means planning around your last frost date, watching soil temperature, and—if you start from seed—counting backwards to give seedlings time to grow indoors. The practical guidance below explains how to time each step for your climate and variety.

Key signals to wait for before planting

Frost risk and last frost date

Tomatoes are frost‑tender. The single most useful calendar anchor is your area's last spring frost date because planting before that risks freeze damage. If you do not know your local date, use a reliable source to Find your last frost date for a starting point.

Soil temperature

Tomatoes prefer consistently warm soil to establish quickly. Measure soil temperature at root depth with a simple probe thermometer on a sunny morning; avoid planting until the soil reads in the comfortable range for your chosen variety. Prepare the bed ahead; see a basic Soil prep checklist to improve drainage and warmth.

Nighttime air temperature

Night lows repeatedly below about 50 to 55 degrees Fahrenheit slow growth and can set plants back. Many gardeners wait until nights are reliably above those thresholds before moving plants outdoors. If you expect occasional cool spring nights, be ready with row covers or cloches for temporary protection.

Timing methods: seeds versus transplants

Start seeds indoors

Starting from seed gives more variety options and a longer production window, but it requires timing. If you plan to Start seeds indoors, calculate backwards from your target transplant date: most varieties need 5 to 8 weeks indoors before moving outside, plus a week or two for hardening off.

Decide your target outdoor transplant date (see the worked example below to compute this).
Count back 5 to 8 weeks for most determinate or standard varieties; indeterminate or slow-growing heirlooms may need more time.
Allow 7 to 14 days at the end of indoor growth for gradual hardening off outdoors.

Planting nursery transplants

Buying young plants reduces lead time but still requires the same outdoor conditions. Inspect nursery plants for rootbound pots or premature flowering; hold back planting until frosts are past and nights are warm. Harden nursery transplants for several days if they have been grown in greenhouse conditions.

Step-by-step planning process

Use this practical sequence to decide precise dates for your site.

Locate your last frost date using local climate data or the guide to Find your last frost date.
Decide how many days or weeks after that date you will transplant (many gardeners wait 1 to 3 weeks for warmth; earlier planting risks cool nights).
If starting seed, count back 5 to 8 weeks from your planned transplant date and set your indoor sowing date; see Start seeds indoors for detailed timing and light requirements.
Prepare soil in advance using the Soil prep checklist so beds are ready and warm when transplanting.
Plan a 7 to 14 day hardening off period directly before planting outdoors.

Worked example (method, not dates)

This example uses relative timing so you can apply it to your own last frost date. Replace "L" with your local last frost date.

Choose L = your last frost date.
Set target transplant date = L plus 7 to 14 days if you prefer extra warmth; some gardeners use L exactly if nights are consistently mild.
Indoor sow date = target transplant date minus 5 to 8 weeks (plus a week or two for hardening off at the end).

For instance, if your chosen transplant window is two weeks after L, and you plan a 7-week indoor start, sow seeds 7 weeks before that transplant window and harden off in the final 1 to 2 weeks.

Soil and site preparation checklist

Good timing matters, but well-prepared soil makes that timing pay off. Prepare the planting area in advance so it is ready once temperatures permit.

Clear weeds and incorporate organic matter to improve structure and fertility.
Check drainage and raise beds if soil stays cold and wet in spring.
Amend with balanced fertilizer or starter nutrients as recommended for tomatoes.
Add mulch after plants are established to conserve heat and moisture.
Consider black plastic or fabric row covers to warm the soil earlier in cool climates.

Detailed soil steps are covered in the Soil prep checklist.

Common mistakes and how to avoid them

Planting too early: Avoid setting transplants out simply because calendar date arrives. Verify nights and soil are warm.
Neglecting hardening off: Moving tender seedlings directly outdoors often causes shock; gradually expose them over 7 to 14 days.
Following nursery timing blindly: Plants bought at a garden center may be under- or overgrown; adapt your schedule to their condition.
Ignoring variety needs: Some tomatoes need more season length. Review Variety selection advice to match days to maturity to your season.

Quick decision checklist before you plant

Are nightly lows consistently above the minimum for tomato growth? If not, wait or protect plants.
Is the soil temperature at root depth warm and workable? If not, delay planting or use warming techniques.
If starting from seed, have you allowed 5 to 8 weeks indoors plus hardening off? If not, schedule sowing now.
Have you prepared soil and arranged protection against late cold snaps? If not, complete the Soil prep checklist.

Timing matters more than an exact calendar date. Use your local last frost date as a baseline, check soil and night temperatures, plan indoor seed start and hardening off, and prepare beds ahead of time. When in doubt, err on the side of slightly warmer conditions or be ready with temporary protection; healthy early establishment determines productivity through the season.