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Starting tomatoes from seed

Updated on January 14, 2017
Patsybell profile image

I inherited my love of gardening from mother and grandmother. I am a garden blogger, freelance writer, Master Gardener emeritus.

Sow Seed 8 Weeks Before Planting

It's a tomato! Tiny seedlings will grow to 3" before the first transplant.
It's a tomato! Tiny seedlings will grow to 3" before the first transplant. | Source

How to start tomato seeds

You will need:

  1. Tomato seed
  2. Seed starting flats or trays
  3. Adequate light source
  4. Clean soil mix
  • Select tomato seed - These are the biggest advantages of starting from seed. It is more affordable and the huge variety.
  • Seed starting flats - Start with a shallow container made of plastic, wood, Styrofoam. Grandma used a clean, empty butter tub or cottage cheese carton.
  • Select a container at least 2 inches deep. Egg cartons and empty egg shells are not a good choice. Developing the seedling roots need more depth.
  • Choose a commercial soil-less seed starting mix or a good germinating medium. If you are using your own garden soil, pasteurize in the oven for 1 hour at 200° F.

Tomato Seedlings

Seeds should be close to the light to avoid spindly plants.
Seeds should be close to the light to avoid spindly plants. | Source

Start seeds

Moisten the mix with water until all the soil is damp. Fill flats or seed cells with pasteurized seed starting mix.

Sprinkle seeds thinly over flat or drop one or two seeds in each seed starting cell, planting about 1/8th inch deep. Barely cover seed and gently firm seed into germinating mix. Seed depth ¼ ".

Next, cover the flats or cells with a protective lid or with clear plastic wrap to prevent moisture loss. If you have a big enough clear plastic bag, just slip the flat inside.

Wait 7 to 14 days for germination of most tomato seed.

The ideal temperature is 70°. Place a tea towel or a few sheets of newspaper over the seeds for insulation. After a week, check for germination every day.

After germination occurs, loosen or remove the clear plastic to improve circulation and reduce soil borne disease. Transplant seedlings to individual containers or cells in a week or 10 days. Move seedlings to a bright light source 14 – 16 hours a day.

The best growing temperature is 65° – 70° Keep the light source a few inches from the plants to develop healthy, sturdy plants. Continue to water seedlings when the soil is dry to the touch. Take care not to over water to prevent damping off.

  • Damping off is caused when pathogens kill seedlings after germination.

First transplant

When crowded seedlings are 3 inches tall, transplant to deeper individual containers. Thin cells to one plant per cell. To protect fragile roots, use scissors to remove extra seedlings from cells.

Tomato plants need lots of room to branch out. Crowding plants will discourage growth. Transplant little tomato plants from flats into individual 4" pots.

The job of your tomato plant is to develop a strong top growth and root system. Continue to adjust the lights, keeping the source just a few inches from the top of the plants.

Favorite tomatoes by color

Gold Medal
German Johnson
Black Krim
Old German
Sudduth's Brandywine
Paul Robeson
Big Rainbow
Granny Cantrel
This is not your grandmothers garden. We grow a rainbow of tomato colors. Our favorites? Bicolor for taste, size, beauty. Black for flavor, productivity. Most red tomatoes that are our favorite, are really pink.

From seedling to transplant

Sturdy seedlings ready for transplant.
Sturdy seedlings ready for transplant. | Source

Harden off tomato plants in 10 days

Fertilize plants once a week with ¼ strength fertilizer. Gently brush your hand across the top of the seedlings once every day. This will encourage sturdy plant stems.

  • This step is very important. After all your weeks of attention, not hardening of your plants properly could distress the plants. The new plants will take weeks to recover or possibly die.

Home-grown or store-bought, plants should be toughened up before planting them in the garden. Young plants can be sun burned or wind burned without a gradual introduction to the outdoors and full sun.

Cut back on watering and fertilizing the plants a couple of days before you begin the process. Start by taking the young tomato plants out for a few hours in bright shade, keeping them from direct sun and wind.

Each day expand the time the plants are outdoors. Gradually expose them to more and more hours of sun. Eventually leave them out all day. Finally, leave them out all day and all night.

The process of hardening off tomato plants will take about 8 to 10 days. The plants won't grow much during this 10 days. They are becoming stronger and storing food that they will need during the transplant.

Your tomato seedlings are ready for the garden.

What is full sun?

Full sun means at least 6 hours a day. Tomato plants are sun loving plants and thrive an warm weather and long sunny days. It is OK if tomato plants are in the sunshine dawn til dusk.

Plant deep for a good start

Pinch off lower leaves. Plant deep enough that only 4 to 6 inches of the stem  remains above ground.
Pinch off lower leaves. Plant deep enough that only 4 to 6 inches of the stem remains above ground. | Source

In The Ground

Your tomato seedlings are ready for the garden. Starting tomatoes from seed or buying starter plants, the next steps will insure the plants get off to a good start. Follow these hubs for the earliest tomatoes and healthiest plants.

Place plant supports, stakes or cages, when you plant the the transplants to prevent root damage. As the days get warmer, plants will grow quickly. It is much easier to install plant supports when tomato plants are small.

The deeper you plant the tomato the heartier the root system. Roots develop all along the part of the stem that is below the soil line.


Submit a Comment

  • Patsybell profile image

    Patsy Bell Hobson 3 years ago from zone 6a, SEMO

    Expect big fat juicy tomatoes. Buy bacon. I see BLTs in your future!

  • phdast7 profile image

    Theresa Ast 3 years ago from Atlanta, Georgia

    Very helpful, Patsy. I am a newcomer to all this gardening stuff, but I better learn. A friend gave me six tomato plants he had started and they are about six inches tall. Well, a first for everything. :)

  • Jackie Lynnley profile image

    Jackie Lynnley 3 years ago from The Beautiful South

    I am just going to bookmark you for everything! You make it look so easy. Thanks. ^

  • Patsybell profile image

    Patsy Bell Hobson 3 years ago from zone 6a, SEMO

    Homegrown tomatoes is America's garden favorite. I love to share with neighbors who can no longer garden.

  • DDE profile image

    Devika Primić 3 years ago from Dubrovnik, Croatia

    Starting tomatoes from seed is a helpful and informative hub last season we planted from seedling and good tomatoes.

  • Patsybell profile image

    Patsy Bell Hobson 3 years ago from zone 6a, SEMO

    Thank you. I still haven't made a final list of which tomatoes I will grow this year. What kind to you grow?

  • rebeccamealey profile image

    Rebecca Mealey 3 years ago from Northeastern Georgia, USA

    Those tomatoes look so good. I will be glad when it is time to grow them outdoors. Thanks for sharing your method!