How to Start Tomato Plants from Seeds

seedling

Do you want to have the best tomato plants, or just the best tomato plants available locally?

Garden centers and big box stores always have tomato transplants available during the growing season but if you only buy local transplants, you’ll be limited in the variety of tomatoes you can grow.

There are many unique and interesting varieties to try, but our favorite is Heirloom tomato seeds.

Buy carefully anytime that you buy seeds, though. You want to make sure your seeds are fresh because as they age, germination decreases. You may want to share a package of seeds with a gardening friend if you’re not going to use them all this year. If you store seeds from year to year, put them in a closed container and store in the refrigerator.

Start your tomato seeds 6-8 weeks before the last expected frost date for your area. The night temperatures should be no lower than the mid-50’s when you put your new transplants in the ground so if you have unpredictable cold weather, it’s best to wait and keep your plants inside.


Materials Needed for Starting Seeds


  1. A seed tray with insert and a humidity dome. The tray has no holes but the insert has drainage holes and individual sections for each tiny plant

  2. Sterile seed starting mix. Seed starting mix has better drainage than regular potting soil allowing for better root development. You can use regular potting soil by adding about 20% coarse vermiculite to the mix. Germinating seeds are very susceptible to soil-borne disease so use good, sterile soils and clean seed trays.

  3. A chopstick or pencil

  4. A spray bottle of water

Now that you know what you need to plant your seeds, let’s talk about what you need to do in order to give them the best start possible.


Directions


  1. Moisten the soil. You don’t want it wet, just damp. You shouldn’t be able to wring water out when you squeeze a handful of the soil.

  2. Loosely fill the insert with the moistened soil. Do not compact soil.

  3. Using the chopstick or pencil, make a hole ¼ inch deep (check your seed package for depth) in each seed compartment. Do not make the hole too deep.

  4. Carefully place 1 seed in each hole at the depth specified on the package and gently cover with loose soil. Do not pant too deep.

  5. When all seeds are planted, spray with water soluble fertilizer at ¼ the recommended strength and cover with the dome.

  6. Place the dome in a warm (75-80 degrees) place and wait for the seeds to germinate. If the soil dries out, spray again this time with ½ strength fertilizer mix.

  7. When you see germination starting, you must provide a light source such as florescent bulbs or a sunny window. If you’re using artificial lighting, they need 12-16 hours per day. As the surface dries out, give each plant a dose of liquid fertilizer. You may use a weak solution of fish emulsion or any plant food with micronutrients. (check the label). Keep the surface moist but don’t overwater. Water each cell individually as it needs it.

Remember that at this stage you have a baby plant so monitor carefully. Let the seedlings dry out a bit and then water. Don’t over water. Turn the tray around if the plants are leaning towards the light. The first leaves are the “cotyledon” or baby leaves. When you see the first true leaves (not the baby leaves), you should transplant your plants to 4 inch pots for further development.

Baby tomato plants with "cotyledon" or baby leaves.

Baby tomato plants with “cotyledon” or baby leaves.

Growing your own seedlings for transplant is a rewarding project. You’ll be able to get a head start on the growing season and will be assured that your transplants aren’t stressed and have been grown in optimal conditions, so the fruit that they bear will be the best possible.

To learn how to transplant your seedlings from the seed pots to a 4-inch pot, check out our next article, From Seedling Tray to 4” Pot.

If you’re starting your own seeds, we’d love to hear from you in the comments section below.

Comments from Other Gardeners
  • Mary Anne says:

    This is the first year I have started tomatoes from seeds and the plants I started from seeds are looking better than the transplants I bought from the nursery. The trick is you have to really baby them because they are in fact babies. Don’t over water, don’t underwater. Treat each plant as an individual. As soon as you see leaves, give the a drink of 1/2 strength liquid fertilizer with micro-nutrients. Good luck!

  • Amy says:

    Never before have I tried to grow tomatoes from seed but this article made it easy. I grew some heirloom varieties that I could never find in garden centers but are everywhere online. The advice about moistening the potting soil is great for all planting. I didn’t even have what I thought was a great light source, just my kitchen overhead light, but they still sprouted and grew well.

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