When To Start Tomato Seeds

Start tomato seeds indoors or in a greenhouse (find greenhouse plans) before planting season. When spring comes, seedlings will be ready to plant outdoors. Plus you'll grow a more successful crop than if you sow them directly in the garden.

What's the best seed starting date?

Start too early and your plants will outgrow their pots quickly and become leggy, root-bound, and weak. They’ll spend their first weeks in the garden regaining strength, rather than producing new leaf growth and flowers.

Start your seeds late and you can have a delayed crop.

By mid-winter, most gardeners are itching to get growing. Have patience to not start too early.

Start dates differ from region to region

Timing your tomato seed starting is not a one-size-fits-all. Much depends on your climate.

How to know when to start tomato seeds

Try these 2 easy steps to calculate the best time to start your seeds where you live.

  1. Determine the last frost date for your region. If you’re not sure, contact your local extension office. You can also view the freeze/frost information provided by the National Climatic Data Center
  2. Count back 4-6 weeks from the last frost date for your region to know when to start your tomatoes.

Plant your tomato seedlings outdoors 1-2 weeks after the last frost date

Waiting longer to plant after the last frost date will reduce the chance of losing your tomato crop to freeze and will allow the ground to warm – which is the kind of environment in which tomatoes do best!

Sample calculation
The last frost date in upstate South Carolina: April 15
Ideal tomato seed starting date: March 1
When to plant tomato seedlings: April 25-May 7

From our readers:

Dear Tomato Dirt,
Why should I wait a couple of weeks after the last frost date to plant my seedlings in the garden? I want to get my tomato plants in the ground as soon as I can so I can have the first tomato on the block.
Sincerely, Itchy Garden Gloves

Dear Itchy,
Tomatoes like hot weather. They don’t like wet feet and they don’t like to be cold. Give the ground a chance to warm up and your tomatoes will reward you. Go with the calendar even if you're impatient.

If you absolutely must plant early, then use the “Black Plastic Trick.” Two to three weeks before setting tomatoes in the garden, cover your planting area with black garden plastic. Black absorbs heat from the sun and will warm your soil more quickly than if it is left to nature’s devices.

Happy gardening!
Sincerely, Tomato Dirt

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