The cutoff depends on your first frost date, not the calendar
You can plant tomatoes too late if you sow them fewer than 85 days before your area's first expected frost. Tomatoes need roughly 85 to 100 days from transplant to mature fruit, depending on the variety. If frost arrives before your plants produce ripe tomatoes, the cold will kill them and you'll lose the crop.
Your first frost date is the average date when temperatures drop to 32°F (0°C) in fall. This date varies by region—it might be September 15 in Minnesota, October 30 in Tennessee, or November 15 in southern California. You can find your first frost date by searching "first frost date" plus your zip code, or by checking your local cooperative extension office website.
Once you know that date, count backward 85 to 100 days. That's your important date for transplanting seedlings into the ground. If you're starting from seed indoors, add another 6 to 8 weeks, since seedlings need that long to grow large enough to plant outside.
Key Takeaways
- Tomatoes need 85 to 100 days from transplant to ripe fruit, so you must plant seedlings at least that many days before your first frost date.
- Find your first frost date by searching your zip code online or contacting your local cooperative extension office.
- If you're starting from seed indoors, add 6 to 8 weeks to your transplant important date to account for seedling growth.
- Determinate (bush) varieties mature faster than indeterminate (vining) types, so they may still work if you're cutting it close.
- Frost cloth and row covers can extend your season by a few weeks if you plant just slightly late, but they won't save a crop planted too close to the first frost date.
How to count backward from your first frost date
Start with your first frost date. If it's October 15, count back 85 days. That lands around July 22. Any tomato seedling transplanted into the ground after July 22 will likely not have time to produce ripe fruit before frost kills the plant.
If you want to be conservative, count back 100 days instead of 85. This gives slower varieties and plants that face early cold snaps a better chance. For October 15, that would be around June 7. Planting by early June gives you a safety margin.
Write the important date on a calendar or set a phone reminder. Many gardeners miss the window because they assume they have more time than they actually do. Late spring feels like there's plenty of summer ahead, but the math doesn't lie.
Determinate versus indeterminate varieties matter
Determinate (bush) tomatoes grow to a fixed size, flower all at once, and produce most of their fruit within a narrow window—usually 60 to 80 days from transplant. Indeterminate (vining) tomatoes keep growing and producing fruit all season long and need the full 85 to 100 days or more to give you a real harvest.
If you're running late, choose a determinate variety. 'Roma', 'San Marzano', 'Mountain Magic', and 'Early Girl' are determinate types that mature in 60 to 75 days. They won't give you tomatoes all summer, but they'll give you a crop before frost if you plant them by late July or early August in most climates.
Indeterminate types like 'Brandywine', 'Cherokee Purple', and 'Sungold' need the full season. If your first frost date is October 15 and you plant an indeterminate seedling on August 1, you'll have flowers and small green fruit when frost arrives, but few ripe tomatoes.
What happens if you plant after the important date
If you transplant seedlings after your 85-day window closes, the plants will grow and flower, but frost will arrive before the fruit ripens. You'll have green tomatoes on the vine when temperatures drop below 50°F at night, which slows ripening dramatically. Below 32°F, the entire plant dies.
Green tomatoes can ripen indoors if you pick them before hard frost and place them on a windowsill or in a paper bag at room temperature. This works for a few weeks, but the flavor won't match tomatoes that ripened on the vine. The longer a tomato stays on the plant before picking, the better it tastes.
If you've already planted too late and frost is coming, harvest all fruit—ripe and green—before the first hard freeze. Frost-damaged tomatoes soften quickly and rot within days.
Extending the season with frost protection
Frost cloth, row covers, and cold frames can buy you 2 to 4 weeks of extra growing time if you plant slightly late. These materials trap heat and protect plants from light frosts (down to about 28°F). They won't protect against a hard freeze, but they can help if your first frost date is uncertain or if you're only a few weeks behind schedule.
Drape frost cloth directly over plants or use stakes to hold it above the foliage so it doesn't touch the leaves. Remove it during the day if temperatures rise above 70°F, or the plants will overheat. Water the soil before covering, since wet soil holds heat better than dry soil.
This approach works best for determinate varieties planted in late July or early August. It's less reliable for indeterminate types planted in September, because even with protection, the plants won't have enough warm days to produce much fruit.
Regional planting important date for common areas
These are rough guidelines based on typical first frost dates. Your actual important date depends on your specific location and the variety you choose. Always check your local first frost date to be sure.
| Region | Typical First Frost Date | Latest Transplant Date (85 days back) |
|---|---|---|
| Upper Midwest (Minnesota, Wisconsin) | September 15 | Late June |
| Mid-Atlantic (Pennsylvania, Virginia) | October 15 | Late July |
| Upper South (Tennessee, Kentucky) | October 30 | Mid-August |
| Lower South (Georgia, South Carolina) | November 15 | Late August |
| Southwest (Arizona, New Mexico) | November 1 | Mid-August |
Starting from seed indoors versus buying transplants
If you're starting tomatoes from seed indoors, you need to begin 6 to 8 weeks before your transplant important date. For a late-July transplant date, start seeds indoors in early June. For a late-August important date, start in mid-July.
Buying seedlings from a nursery or garden center skips the indoor seed-starting phase, so you can plant them directly into the ground closer to your important date. If you realize you're running late, buying 6-week-old transplants is faster than waiting for seeds to germinate and grow. Nursery seedlings are usually ready to transplant within 2 to 3 weeks of purchase.
Check the label on nursery seedlings for the days-to-maturity number. If it says 75 days and your first frost date is 60 days away, that variety won't work. Choose one labeled 60 days or fewer.
Frequently Asked Questions
Can I plant tomatoes in August and still get a harvest?
It depends on your first frost date and the variety. In areas with a first frost date of October 30 or later, you can plant determinate varieties in mid-August and harvest in October. In areas with an earlier frost date (September 15 or earlier), August planting is too late for most varieties. Check your first frost date and count backward 85 days to see if August planting works for you.
What's the difference between days to maturity on the seed packet and days to first ripe tomato?
Days to maturity usually means days from transplant to the first ripe fruit, not from seed. If a packet says 75 days, that's 75 days after you move the seedling into the garden. If you're starting from seed, add 6 to 8 weeks to that number. Some packets specify "days from seed" or "days from transplant," so read carefully.
If I plant too late and get green tomatoes, can I ripen them indoors?
Yes, green tomatoes will ripen indoors at room temperature over 2 to 4 weeks. Pick them before hard frost and place them in a paper bag or on a windowsill. They won't taste as good as vine-ripened fruit, but they're better than losing the crop entirely. Tomatoes picked after frost damage will rot quickly and won't ripen properly.
Do I need to know my exact first frost date, or is a range okay?
A range is fine for planning. Your local cooperative extension office usually gives a range (like September 10 to 20), not a single date. Use the earlier date in the range to be safe. If you plant by that date, you'll almost certainly have time for a full harvest.
Can I grow tomatoes in a container to extend the season?
Container tomatoes mature at the same rate as in-ground plants, so containers don't solve the late-planting problem. However, you can move containers indoors or under cover if frost threatens, which gives you a few extra weeks of protection. This works best for determinate varieties and smaller pots that you can actually move.