Starting Tomatoes from Seed: Tips & Tricks

Published on March 03, 2021

New gardeners often feel daunted by the idea of starting tomatoes from seed, but it’s not as hard as you think!

There are many reasons to start your tomatoes from seed:

  • Seeds give you access to more varieties than you can buy locally at the store.
  • You have more control over the conditions the plants are grown in.
  • In the long run, starting from seed can save you money, too.
  • Plus, it’s fun to start your tomatoes from seed! That’s probably the best reason of all.

Starting your tomatoes at home is a perfect way to enjoy the fun of gardening while you’re waiting for the weather to warm up.

planting seeds indoors with grow lights

Step one: cleaning!

The first step in starting your tomatoes from seed is pathogen prevention. This means using sterilized pots or trays, as well as a sterile growing medium.

If you’re reusing pots from previous years, a soak in a 10% solution of household bleach for 30 minutes will be enough. A soilless medium works well for germination. Press the seeds into the growing medium until they are buried very shallowly – about ¼”.

You might be tempted to add some fertilizer to your growing medium.


The fertilizing salts could prevent or slow germination, so be patient. You’ll get there.

Setting up your growing environment

Tomatoes do not require light to germinate, but keeping them consistently warm is helpful.

A germination temperature of 70-80° is best for optimal germination. Mist your seeds to keep them moist, but not wet. A humidity dome will help you to retain this needed moisture. Keep the dome on until the seeds begin to sprout, usually in 7-14 days.

Once the seeds germinate

After germination, you can take off the humidity dome to avoid any damping off.

Now you can also fertilize. Water with a half dose of fertilizer the first week, and move up to full strength afterward. You’ll also need to provide strong lights for your tomato seedlings. They need to be quite close to the lights – just a few inches away.

True leaves = time to pot up!

Your tomatoes will soon develop their first true leaves. These look a little different than the cotyledons that first emerge.

True leaves have the appearance of a mature tomato plant’s leaves.

tomatoes growing from seed indoors

Once there are four of them, it’s time to pot your tomato plants up.

Transplant deeply to a larger pot. This is so the tomato will develop a stronger root system.

Hardening off your tomato plants

The last step before your tomatoes move completely outside is hardening off.

This period of adjustment is important for your plants to get used to the conditions outdoors. Do it gradually, over a week or two. Choose a mild day and shield your plants from wind and harsh sun. Increase the amount of time exposed to outdoor conditions gradually at the same time as decreasing the protection.

One last word of advice: don’t get so excited about your tomatoes that you rush to put them outdoors before the weather warms up.

Temperatures over 60° are important for proper growth and healthy tomatoes. Be patient so that all of your hard work pays off. Before you know it, you’ll be rewarded with juicy, delicious tomatoes you grew yourself!

Written by Teresa Chandler
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