Starting tomatoes from seed

Learn to start tomatoes from seed and report them correctly.
Our tomato seedlings after potting up into larger containers.

Tomatoes hold a special place in the hearts of many gardeners. They require pruning and extra protection from the elements. They’re susceptible to a host of diseases and are generally more challenging to grow than, say, lettuce or kale. But the prospect of fresh, juicy fruits picked right off the vine is totally worth the extra work.

By planting tomatoes from seed (rather than buying starts), you open up a whole new world of colours and flavours. There are cherries in yellow, purple and orange, striped green zebras, and gnarled, sweet heirlooms. There are tomatoes best-suited to eating right away, and others that are ideal for canning and sauces. Some have been developed especially for growing in containers, while others produce enormous vines that require eight-foot trellises. Can’t decide? Choose hardy, disease-resistant, tasty varieties, and consider getting two types — an early one and a late one — for a longer harvest.

In most parts of the world, tomatoes need to be started indoors. Mid-March is the perfect time here on the west coast, though if you’re ambitious, have access to a greenhouse and select a super-early parthenocarpic (seedless) variety, you can experiment with dates as early as mid-February. Search online for planting calendars for your area. 

Learn to start tomatoes from seed and report them correctly.
These are the same tomato seedlings as in the picture above. They look so much taller before repotting!

Starting tomatoes from seed

  • Seedling soil
  • A leak-proof tray
  • 24-cell seed-starting flats, or disposable coffee cups with holes poked in the bottom
  • A clear plastic dome or salad-mix shell
  • A height-adjustable seed-starting kit or a very sunny window
  • A seedling heating mat (optional)
  • Tomato seeds!
  • Ground cinnamon (optional)
  • Label stickers or masking tape
  • Fan or air filter (optional)
  • Potting soil
  • Medium-sized plastic flower pots or large yogurt containers with holes poked in the bottom.

Fill your seed-starting flats (or coffee cups) with seedling soil right up to the top. Seedling soil is light-weight, retains moisture, and will get your seeds off to a healthier start than regular potting soil. Set your pots into the leak-proof tray and pour water into it so that your pots can absorb moisture from the bottom. Leave them until the soil has rehydrated, adding more water as needed (it can take a day or so).

Once the soil is evenly moist, plant your seeds according to the package directions, two seeds per cup. Pat the soil down gently. Label each cup with the variety and date (don’t skip that step!) 

To help prevent mold, sprinkle a bit of cinnamon over the tops of your cups. Then cover your seeds with a clear plastic dome and keep a close eye on them for the next few days. Want your seeds to grow faster? Place a seed-starting heating mat underneath.

As soon as you see some activity above the surface, remove the dome and set your seeds under a seed-starting light or in front of a very bright, large window. If you’re using an artificial light, position it just a couple of inches above the seedlings, and adjust it as they grow taller. Leave the light on for twelve to sixteen hours per day. To prevent mold and ensure strong seedlings, make sure there’s lots of air-flow in the room. Set up a fan or air filter if you can, aimed so that the seedlings waft just a tiny bit in the light “breeze”.

At about three weeks of age, your seedlings will have your first “adult leaves” and will be ready to move into bigger pots. Sorry, but if your cup has more than one sprout, you’ll need to cut the extras out. Grab some regular potting soil and medium-sized plastic flower pots or yogurt containers, and plant your seedlings very deep. You want to bury most of the stem, just letting the leaves poke out. Roots will grow out of the buried part of the stem, ensuring a sturdier plant.

After re-potting, return your seedlings to their light and give them about three more weeks to grow. Water them gently as needed, avoiding wetting the leaves.

Stay tuned for instructions on how to transition your seedlings out into the real world!

Learn to start tomatoes from seed and report them correctly.

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