It is generally said to sow tomato seeds after unexpected spring frost. And that is absolutely right planting time for tomato seeds. But stop! When it comes to the question “When is the best time to plant tomato seeds in YOUR AREA”, then you must be aware before digging dirt.
Two main factors (plant variety and regional climate) decide the planting time of any crop in your area. Although tomato varieties have little difference in their growth period, the right planting time is dependent on your local climate, especially the last frost date in your area.
When is the Best Time to Plant Tomato Seeds?
The best time to plant tomato seeds is mid to late spring, but it may vary for you from others in your area and for your chosen tomato variety. Here’s how
Tomato Variety
Its varieties do not directly change the best time to plant tomato seeds. However, seed starting time can be more fine-tuned with their different growth cycle periods and maximum or minimum temperature tolerances.
Season Preference
For tomato seed germination, 10 to 15 Celcius is the ideal temperature, whether there is any tomato variety. Not just that, 21 to 27 Celcius is considered the optimal range for vegetative and reproductive growth for all tomato varieties.
Do you Know? According to HGTV, 10 to 15C is the only minimum temperature range for seed germination. Lower than 10C causes poor germination, similarly, above than 25C also negatively affects the germination process.
Tolerance Range
Many resources describe different minimal survival limits for different tomato varieties, as WIKIPEDIA agrees that 4C minimal temperature tolerance for EARLY GIRL TOMATO, but don’t misunderstand to mean that for seed germination.
Note: Temperature tolerant, whether it’s maximum or minimum, doesn’t mean that the plant will grow well, it just means it will not die.
Growth Cycle
Generally, tomatoes take 90 to 120 days to grow from seed to fruit harvest (here growth cycle). It means that for direct sowing outdoors, you need enough growing season in which;
- Minimum 90 Frost Free Days
- The average day temperature should be 18 to 30C
- The average nighttime temperature should be 12C or above
So, here, you have to choose tomato varieties that can get the proper growing conditions in your area to give a good yield at the right time.
The table showcases recommended varieties for colder areas with short growing seasons and warmer regions with long growing seasons.
| Property | Colder Areas (Short Growing Season) | Warmer Areas (Long Growing Season) |
|---|---|---|
| Variety Name |
Early Girl Sub Arctic Plenty Siberian Glacier Oregon Spring |
Celebrity San Marzano Super Sweet 100 Homestead Sungold |
| Maturity Time (Days) |
50-62 42 58 55 58-60 |
70-75 85 65-70 80 57 |
| Planting Time |
Indoor seed starting 6-8 weeks before last frost Transplant outdoors after last frost date Typically late spring |
Direct sow or transplant after danger of frost Early spring to late spring Can be extended into summer |
| Indoor/Outdoor Transplanting |
Indoor seed start recommended Transplant outdoors post frost |
Can be direct sown outdoors Transplanting also common |
| General Planting Season |
Short growing season: Plant indoors early spring, transplant outdoors after frost (late spring) |
Long growing season: Plant directly outdoors or start indoors in early spring, grow through summer |
Result: Direct tomato seed sowing will succeed in areas where the growing season lasts for 3 months or more. Otherwise, you can sow tomato seeds indoors and then transplant them outdoors for two reasons;
- If your area experiences a short growing season
- Or, If you want an early harvest
Final results of the effect of tomato variety on its seeds sowing Time
Whether you live in any area, if the variety you choose does not meet your local climate and growing season, its growth period from planting to harvesting may be negatively affected.
Regional Climate
After considering tomato variety, you need to look at your regional climate to determine best time to plant tomato seeds. It is common sense that, at the same time, frost dates and soil temperature vary in different areas. In your area, you should consider;
- Frost Dates
- Growing Season
- Soil Temperature
Frost Dates, Growing Season, and Soil Temperature
Frost dates and duration highly affect the best time to plant tomato seeds. If the minimum frost temperature reaches 0 Centigrade, tomato seeds will not germinate.
Protecting tomato seedlings from outdoor frost is crucial. However, you can make seedlings indoors 4 to 5 weeks before the first frost date for transplanting outdoors as the weather warms up.
Colder Areas (USDA zones 3 to 7)
Frost usually comes early and goes late in colder areas, such as North East America (Alaska) and Europe, where last spring frost stays until the end of May.
Do you Know? UNH (University of New Hampshire) recommends transplanting tomato seedlings outdoors in Hampshire (USA) on the Weekend of Memorial Day. Living in South America, you can do this two weeks ago, while Northern gardeners have to wait until mid-June.
Commercial farmers sow tomato seeds from February to April in a greenhouse and then transplant seedlings outdoors when the soil temperature reaches 15C in these colder areas.
Warmer Areas (USDA Zones 8 to 10)
On the other hand, in warmer areas, such as Florida, Texas, Pakistan, and Southern California, the frost period is usually short or during winters. There, tomato seeds can be planted from October to February or January to March.
Do you know? The University of Florida says to sow tomato seeds in late winter to early spring when colder countries have covered with snow. Living in Punjab (Pakistan), I sow my tomato seeds from March to April.
These factors are largely under consideration in warmer areas, especially for commercial farming. It can be furthered and controlled through greenhouses and other climate management techniques.
When to Plant Tomato Seed USDA Zones?
According to the first and last Frost dates by zone (Park Seed), from April to June is ideal for USDA zones 3, 4, 5, 6, and 7, while from January to March is good for zones 8, 9, and 10 to plant tomato seeds.
| Zone Number | Planting Time | Last Frost Date | Growing Season Period | Suitable Tomato Variety Name |
|---|---|---|---|---|
| 3 | Late May to Early June | May 1st to 31st | 90 to 120 days | Glacier, Siberian, Sub-Arctic Plenty |
| 4 | Late May to Early June | May 1st to 31st | 100 to 130 days | Early Girl, Manitoba, Bush Beefsteak |
| 5 | Mid to Late April | April 30th | 120 to 150 days | Celebrity, Oregon Spring, Roma |
| 6 | Early to Mid April | April 30th | 140 to 170 days | Better Boy, Mountain Fresh, Brandywine |
| 7 | Late March to Early April | March 30th | 150 to 180 days | Rutgers, Cherokee Purple, Black Krim |
| 8 | Late February to Mid March | March 30th | 180 to 210 days | Big Boy, San Marzano, Yellow Pear |
| 9 | Late January to Mid February | February 28th | 210 to 250 days | Homestead, Solar Fire, Super Fantastic |
| 10 | January to February | January 30th or earlier | 250 to 300+ days | Beefsteak, Green Zebra, Mortgage Lifter |
When & Where to Plant Tomato Seeds?
You should still examine the above factors when planting tomatoes indoors or outdoors.
Basic Definitions
- Indoor tomato planting means sowing seeds indoors during the frost period but before 4 to 5 weeks ago. However, if frost still lasts in the spring, you can delay more than 5 weeks.
- Outdoor tomato planting means directly sowing seeds in outdoor garden soil or outdoor containers/pots when soil and air temperatures consistently stay above 10C.
When to Plant Tomato Seeds Indoor?
When you LIVE in USDA Zone 3 to 7, but still examine the following situation;
- When the frost comes early and goes late in YOUR AREA
- When your area experiences a short growing season.
- When you want an early harvest of tomato plants.
- When you have chosen a tomato variety that matures after 70 to 80 days.
- Last and most considerable, when outdoor temperature is less than 10C.
When to Plant Tomato Seeds Outdoor?
When you LIVE in USDA zone 8 to 10, still consider the following conditions;
- When YOUR AREA experiences short frost duration, which goes early.
- When YOUR AREA experiences a long growing season
- When soil and air temperature is 10 to 15 Celcius.
- When you have to transplant indoor tomato seedlings.
Celebration for frost-free areas🥳: If you live in USDA zones 9 to 13 (such as South Florida, South California, South part of Texas), then you have a chance to grow tomatoes year-round (Tomato seeds may be planted two times: spring and early fall). You can also choose indeterminate and long-maturity tomato varieties.
Final Thoughts: When is the Best Time to Plant Tomato Seeds
To extract the best time to sow tomato seeds:
- First of all, choose the right tomato variety according to your growing season and temperature trend.
- Determine the best planting time based on tomato variety (its growth cycle and temperature tolerances).
- Third and most important, consider local climate, last frost dates, and growing season length.
- Lastly, compare both factors from each other and decide which tomato variety will grow best in your area and when to plant its seeds.
Remember!
- 10C to 15C is ideal for seed germination
- 18/21 to 27C optimal range for vegetative and reproductive growth
- Consistent temperatures below 10C and above 30C cause poor yield.
Finally, you will have a more suitable planting time than the general, according to your local climate, growing season length, frost dates, and day/nighttime temperature trends.
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