Growing Tomatoes from Seed

Growing Tomatoes from Seed

Kathryn Wright
Apr 23, 2010

Growing your own tomatoes was recently covered by Emily Ho, but I wanted to focus specifically on starting tomatoes from seed. Growing from seed ensures that your plants are grown organically and locally, but the best thing about growing from seed is that you can give your extra plants as gifts throughout the growing season. A small tomato bush in a terra cotta pot could not make a prettier or more practical gift.

For the past three years I have been growing tomatoes from seed, starting them indoors in my apartment in early spring and moving them outside when the weather warms up. It can be tricky without the right set-up, so here is what I have learned.


Starting seeds:

  • Start seeds indoors as early as 4-6 weeks before the last frost - in your region you may already be closer than that, but as long as you start by mid-May you can still have a great tomato crop.
  • Young tomato plants need light and warmth - a fluorescent light provides lots of light and enough warmth without burning the plants. You can easily grow the plants under a table lamp. The light should be about 12"-16" away from the plants 24 hours a day.
  • Soak seeds overnight in cooled chamomile tea before planting – this helps germinate and acts as a fungicide.
  • Start your seeds in sterilized soil - You'll either need to buy potting soil or sterilize soil from your garden by baking it at 400F for 15 minutes, this kills any fungi or other seeds in the soil that might compete with your plants. You can also mix crushed eggshells in the potting soil to aerates the soil and help productivity.
  • Start about five seeds in each pot for every one plant you intend to grow - a few will die along the way and weaker plants should be pinched-off.


  • Prevent damping-off – often fungus may grow on the surface of wet soil causing plants to collapse and die. Once you have damping-off it can spread to other plants and your affected plant can't be salvaged. A few ways to prevent it are:
    - Lightly cover the top of the soil with sand.
    - Add a pinch of cinnamon to the surface.
    - Water your plants with cooled chamomile tea.
  • DON'T OVER-WATER - over-watering can also cause damping-off. Only water young tomato plants when they start to droop, usually every few days. And, if possible water them from underneath instead of pouring water all over the surface. This is very important it's in our nature to keep 'em wet, but you must resist!
  • Pinch off the weaker plants - I don't like to kill my little babies, but it helps stronger plants thrive.
  • Don't fertilize until the plants have 2-3 sets of leaves - fertilizing too early causes the stalks to grow quickly causing weaker, leggy plants that can't hold large tomatoes.

Transplanting outdoors:

  • Harden-off your plants - prepare your plants for the shock of cool outdoor weather by leaving them outdoors for one or two hours per day and slowly build up to eight hours before transplanting outside.
  • Create a "cloche" if the evenings are still quite cold - A cloche is a shelter for a plant, you can make one by cutting the bottom off of a 2L plastic bottle in and pressing into the soil over your plant in the evening.

That's what I know, but please share your own tips or techniques in commenting!

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