Plant tomatoes before your first frost date, not after

The latest you can plant tomatoes depends on when your first frost arrives in fall. Tomatoes need 60 to 85 days from planting to produce ripe fruit, depending on the variety. If you know your first frost date, count backward 85 days—that is your absolute important date for planting if you want to harvest before cold kills the plants.

For example, if your first frost typically arrives on October 15, your last planting date is around July 22. Plant later than that, and the plants will flower and set fruit, but the tomatoes will still be green when frost arrives. You can pick them green and ripen them indoors, but they will not develop the same flavor as vine-ripened fruit.

Find your first frost date by searching "[your city] first frost date" or checking the USDA Plant Hardiness Zone Map. Your local cooperative extension office also has this information and can tell you the average date for your specific area.

Key Takeaways

  • Count backward 85 days from your first frost date to find your latest safe planting date for tomatoes that will ripen on the vine.
  • Tomato varieties labeled "early" or "short season" mature in 60 to 70 days, giving you a later planting window than full-size varieties.
  • Planting in late summer works only if you start with transplants (small plants from a nursery), not seeds, because seeds take 6 to 8 weeks to become large enough to plant outside.
  • Green tomatoes picked before frost will ripen indoors in a warm, dark place over two to four weeks, so a late harvest is not a total loss.

Early varieties give you more time

If your frost date is early or you live in a short-season climate, choose tomato varieties bred to mature quickly. Varieties like 'Early Girl', 'Siberia', 'Sub-Arctic Plenty', and 'Glacier' produce ripe fruit in 55 to 70 days instead of 80 to 90. This extra window can mean the difference between a harvest and a crop that never ripens.

Check the seed packet or plant label for the number of days to maturity. This number tells you how long the plant takes from transplant to first ripe fruit. A 60-day variety planted on July 1 will produce ripe tomatoes by late August, even in a climate with an early October frost.

Heirloom and large-fruited varieties almost always take longer—often 80 to 95 days. If you want those, plant them earlier in the season, not later.

Start with transplants, not seeds, for late planting

If you are planting in late June or July, you must use transplants (small plants from a nursery), not seeds. Tomato seeds take 6 to 8 weeks to grow into plants large enough to move outside. By the time a seed-grown plant is ready to plant, your frost date will have arrived.

Transplants are already 6 to 8 inches tall and have a root system. You can plant them directly in the ground and they will start flowering within two to three weeks. This compressed timeline is the only way to get a late-season tomato crop.

Buy transplants from a local nursery rather than ordering seeds online. Nurseries stock transplants in late spring and early summer, timed for your region's planting season. If you cannot find them locally, some mail-order seed companies sell transplants, but shipping delays can eat into your narrow window.

Soil temperature matters as much as air temperature

Tomatoes will not grow in cold soil, even if the air is warm. Soil below 60°F slows root development dramatically. Below 50°F, the plant essentially stops growing. If you plant a transplant into soil that is still cool from spring, it will sit dormant for weeks.

In late summer, soil temperature is usually not a problem—it stays warm through August and into September in most climates. But if you are planting in a shaded spot or in a location that cools quickly in the evening, check the soil temperature with a straightforward soil thermometer before planting. Aim for soil at least 60°F, ideally 65°F or warmer.

Protect late-planted tomatoes from early frost

If you plant close to your frost date, you are gambling that an early frost will not arrive before the fruit ripens. You can improve your odds with straightforward frost protection. Row covers (lightweight fabric you drape over plants) can add 2 to 4 degrees of protection on a light frost night. Plastic sheeting held up with stakes works too, though it can trap too much heat on warm days.

Water the soil deeply the day before a predicted frost. Wet soil holds heat better than dry soil and releases it slowly at night, warming the air around the plant. This small step can be the difference between a plant that survives a 32°F night and one that does not.

If frost does arrive and damages the plant, do not pull it out when ready. Tomatoes are tough—a light frost may kill the leaves but not the stems. The plant may recover and produce new growth if temperatures warm again.

Harvest green tomatoes and ripen them indoors

If frost arrives before your tomatoes are ripe, pick all the fruit—both ripe and green—before the temperature drops below 50°F. Frost damage makes tomatoes mealy and inedible, but a green tomato picked before frost will ripen indoors.

Place green tomatoes in a cardboard box or paper bag in a warm room (65°F to 75°F is ideal) away from direct sunlight. They will ripen over two to four weeks. You can speed this up slightly by placing a ripe banana or apple in the box with them—the ethylene gas these fruits release triggers ripening in tomatoes.

Tomatoes ripened indoors will not taste exactly like vine-ripened fruit, but they will be edible and reasonably flavorful. The longer they spend on the vine before picking, the better the final flavor, so this is another reason to plant as early in the season as you can.

Frequently Asked Questions

Can I plant tomatoes in August where I live?

Only if your first frost date is in late October or November, and only with transplants and an early variety. Count backward 85 days from your frost date. If that date is before August 1, planting in August will not give you time for a full harvest. You can still try with a 60-day variety, but the risk is high.

What if I plant too late and the tomatoes do not ripen?

Pick all the fruit before frost, including green ones. Store them in a warm, dark room and they will ripen over two to four weeks. The flavor will be milder than vine-ripened fruit, but they will be usable for cooking or eating fresh.

Does a late frost in spring affect my planting date?

No. Your planting date is determined by your first fall frost, not your last spring frost. A late spring frost only delays when you can plant in spring. Your important date for planting in summer is still set by when cold weather returns in fall.

Can I grow tomatoes indoors if it is too late to plant outside?

Tomatoes need at least 6 to 8 hours of direct sunlight daily to produce fruit. A sunny window usually does not provide enough light. You would need grow lights positioned close to the plants, which is practical for seedlings but expensive for full-sized fruiting plants.

Do cherry tomatoes ripen faster than large tomatoes?

Usually, yes. Cherry tomato varieties often mature in 60 to 75 days, while beefsteak and heirloom varieties take 80 to 95 days. Check the seed packet for the specific variety—some cherry tomatoes are bred for speed, while others are slower.