Tips & Tricks: Starting Tomatoes from Seed for Beginners


New gardeners often feel daunted by the idea of starting tomatoes from seed, but it’s not as hard as you think! Starting your tomatoes at home is the perfect way to enjoy the fun of gardening while you’re waiting for the weather to warm up. And, with our tips and tricks for beginners, you will avoid common mistakes beginners often face.

tomato seedlings

There are many reasons to grow tomatoes from seed rather than buying transplants from your local garden center, including:

  • Access to more varieties than the limited selection available as transplants, including many heirloom varieties you can't find in stores.
  • Control over the conditions the plants are grown in. You can give your tomatoes a great start and not worry they’ve been neglected. 
  • Saving money is a great reason. One packet of seed can cost about the same as a couple of transplants and give you many more plants.
  • Fun is probably the best reason to start your tomatoes from seed! It’s a great way to start the growing season with confidence.

Growing Tomatoes From Seed to Harvest

What do my seeds need for proper germination? What kind of environment is best?

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. Don’t.

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

What about warmth & light?

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.

markers for tomato seeds

My tomato seeds sprouted! What next? 

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

Now you can also fertilize! We told you it wouldn’t take long.

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.

When should I pot up my tomato seedlings?

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. 

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.

tomato seedlings

How do I prepare my tomato plants for transplanting into the garden?

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.

They are ready for the garden. Now what?

One last word of advice: don’t rush the process because you’re getting so excited about your tomatoes! Temperatures over 60° are important for proper growth and healthy tomatoes. Wait to transplant your tomato seedlings into the garden until after the average last spring frost date, and be patient so that all of your hard work pays off. 

Also, be prepared to protect your seedlings with row covers or plant covers (or even a blanket!) if a late frost threatens.

tomatoes growing on vine

Before you know it, you'll be harvesting juicy, delicious tomatoes in eight weeks or less. And you’ll be happy knowing you grew yourself! 

Written by Teresa Chandler