How To Start Tomatoes From Seed

Ah, there is nothing better than a perfectly ripe tomato just picked from the garden! The beautiful tomato that I am envisioning is every tomato lover’s dream. I’m going to show you how to start tomatoes from seed.

It has been said that 95% of home gardeners will have tomatoes in the garden. But it is also said that tomatoes are prone to more problems than most other vegetables.

Is a tomato a fruit or vegetable? Tomatoes are botanically a fruit, but nutritionally it is considered a vegetable. A member of the nightshade family which includes tomatoes, peppers, eggplant, and potatoes, tomatoes originated in Peru. The name tomato translates to “a plump thing with a naval.”

Tomato Varieties

Tomato Varieties red, green, yellow
A Variety of Tomatoes

I read that there are over 3,000 varieties of heirloom tomatoes in active cultivation worldwide, and more than 15,000 known varieties of tomatoes! Who knew? The types of tomatoes that you might be familiar with include beefsteak tomatoes, cherry and grape tomatoes, paste (Roma) tomatoes, and salad tomatoes. Tomatoes are available in different sizes and colors, so you can choose what you like.

Tomatoes have two different growth patterns: determinate and indeterminate.

Determinate tomatoes are short and bushy, growing up to 3 feet high. The buds which are located at the ends of the branches form flowers for a short period of time. The flowers set and form into tomatoes, which ripen within a 1-to-2-week period. Then the plant dies. Determinate tomatoes are perfect for patio tomatoes growing in pots, and you don’t have to stake them. And the crop timing is good for canning as the tomatoes all ripen at once.

Indeterminate tomatoes, on the other hand, grow on vines and will need to be supported by either staking them or caging them. It is possible for indeterminate tomatoes to get as high as 10 feet tall! They will continue growing until they are killed by frost. They have lateral shoots off the main stems that set flowers and fruit. Indeterminate tomatoes produce large crops and will bear fruit for 2-to-3-months. You’ll have delicious tomatoes for all summer!

Start Tomatoes from Seed

Tomatoes are easy to start from seed. If you can start your own, you’ll find the largest assortment of types of tomatoes to choose from. Seeds are very inexpensive to buy and it’s so much fun to raise a plant seed to harvest. Just think about it. You start the seeds in January, transplant the seedlings into the garden in May/June, harvest tomatoes in September.

You’ll need some things to successfully start your seeds.

These are what I use to start my seeds in: mini greenhouse trays with dome and base trays. They work well, and the lids are adjustable for moisture control.

If you want, you can use a heat mat, grow lights, or even a greenhouse to start your seeds with. But you don’t absolutely need these if not.

Plant the Seeds

how to plant seeds for your vegetable garden containers are filled with soil with seed packets
Ready to Plant

You want to be sure to use seedling mix to start the tomato seeds in, not potting mix or soil out of your garden. Seedling mix will encourage strong stems and root growth. Potting mix is too coarse for seedlings, and garden soil could contain bacteria or bugs.

Get your seeds, seedling trays and labels ready. Moisten the seedling mix in the bag or bucket before you put it into the cells. Fill each cell almost to the top with seedling mix, then pat it down to remove any air pockets. Use a pencil or your fingers and make two holes in each cell perhaps ¼” deep. Place one seed in each hole. You will have two seeds per cell, so you can be assured that there will be at least one tomato seedling per cell. Sprinkle some more moist seedling mix over the top to cover the seeds and pat down to remove air pockets. Water with a spritzer and place the dome on top.

Place the trays in a warm environment (65-75 ° F) and keep an eye out for your sprouts. I have seen trays on top of the refrigerator where it’s warm, or in an oven with just the light on. Don’t forget your seedlings are in there before you turn on the oven though!

Care of Seedlings

Once the seedlings sprout, periodically remove the dome over 2 to 3 days. Maintain the temperature at 65-75° F and a grow light at 2” above the seedlings. If you don’t have grow lights, a sunny windowsill works. Blow a fan over the seedlings for a few hours each day to encourage strong stems. Check every day for moisture and use room temperature water to spritz or drip from fingers to moisten the soil.

Fertilize with diluted 1-2-1 fertilizer. This 1-2-1 tells you the ratio of Nitrogen to Phosphorus to Potassium: 1 part Nitrogen, 2 parts Phosphorus, 1 part potassium. Nitrogen is for foliage, Phosphorus is for flowers and fruit, and Potassium is for roots and tubers.

As your seedlings come up, you’ll see two straight leaves on your new seedlings. These first leaves are called cotyledons. They’re not real leaves but are part of the seed embryo. They store food for the seedling before the true leaves appear and photosynthesis starts. They might fall off after the true leaves come out. You’ll know the difference since the true leaves are frillier on the edges.

If your seedlings become leggy, spindly, or tilt, these could be caused by insufficient light, lack of soil moisture, or high temperatures. The stems grow faster than leaves do. Rectify the problem, and the seedlings will become healthy again quickly.

Remember that we have two seedlings in each cell if all the seeds sprouted. You will want to remove one seedling from each cell, so you have only the healthiest one left. To do this you can cut the discarded seedling off at soil level with scissors or snips, and the remaining seedling continues to grow.

Transplant Tomato Seedlings

seedling with roots is ready to transplant
Seedling Ready To Transplant

Your tomato seedlings will be transplanted a couple of times, each time deeper in a larger pot or deeper in the ground when ready. Check to see if the roots are showing around the root ball to determine if it’s time to transplant.

It’s time to transplant out of the starting trays and into their first pot. Water and fertilize with diluted 1-2-1 fertilizer. Remove the seedling from the tray cells, take off the cotyledon leaves, and plant the seedling deeply into the pot, covering the roots with potting mix.

When your tomato starts are 6 – 10” tall, they can be transplanted to the garden if the soil temperature is 55-60° F. If it’s still too cold, they can be transplanted to larger one-gallon pots to wait for the soil to get warm enough. Remember, cooler weather will stunt the plant’s growth and slow it down, warmer weather will encourage growth. I’ve seen tomato plants set out in May during the cooler weather next to tomato plants set out in June when it was warmer. By the end of June, they were both the same size. So, I’ve learned to wait for the warmer weather. It’s hard for me to be patient!

The tomato starts need to be hardened off before they are placed in the garden, giving them an adjustment period to acclimate to outdoor conditions. Start 7 to 10 days before you plant on transplanting them outside, leaving them outside for 3-4 hours, increasing the time every day. Protect them from wind and too much sun and bring them back inside after their time is up.

Garden Location and Preparation

Sunshine is key to growing fabulous tomatoes. Tomatoes like 8+ hours of sun, so make sure your garden is situated so that you have plenty of sunshine every day for them. Tomatoes like rich, loamy, and well-drained soil, so you might need to make improvements to your soil to make a good home for your new tomato starts.

Rotate crops every year to prevent the depletion of soil nutrients, help maintain soil structure, and prevent soil borne pests from getting a foothold in the garden.

When thinking of where you want to plant your tomatoes, avoid planting tomatoes or its family of crops in same location for 3 years. The family includes tomatoes, peppers, eggplant, potatoes. If your space is limited and you can’t rotate, use pots. Another option is to plant grafted tomatoes which are resistant to soil borne diseases. I’ve got two grafted tomato plants in my garden now, and I’ll let you know how they do.

Get the soil ready for your starts. Turn it to 10-12” deep, add organic matter and work in 2-3” deep, aim for a pH 6.8 – 7.2 for tomatoes.

Transplant Into The Garden

OK! It’s time to transplant your tomato starts into the garden. Everything is ready, the soil is 60 degrees, and the plants are hardened off.

Now you must decide what planting method you’ll use: trench or vertical.

The trench planting method is good for strong roots. In the early season there is warmer soil around roots which speeds plant growth. But since the roots are not very deep, they will dry out in summer heat. They will need to be heavily mulched after the soil warms up.

The vertical planting method is what I use. Dig a hole 10-12 inches deep, remove any leaves 5-6 inches above the soil, and plant. In the early season there is cooler soil around the roots and slower growth, but it will be moister in the hot summer heat.

Hydrate the plants, space the holes at least 4 feet apart, and plant. Fertilize with 1-2-1 diluted fertilizer, and place stakes or cages around each plant for support. Indeterminate tomatoes grow up to 8 feet tall in a vine and need to be caged for support. Determinate tomatoes don’t really need cages as they are shorter and bushy.

Once the plants reach about 3 feet tall, remove all leaves from the bottom foot of the stem. These are the oldest leaves and are usually the first to develop fungus disease or touch soilborne pathogens. Removing them helps keep the tomato plants healthy.

Pinch and remove suckers out. These develop in the joint between branches. They won’t bear fruit and take energy away from the rest of the plant. Keep the plants trimmed so that no leaves touch the ground to prevent disease.


With tomato plants, you want to water the roots, not the leaves. Wet leaves can lead to disease and split tomatoes. Try to keep to a consistent schedule and water deeply.

Here are some guidelines for watering:

  • 1” per week in normal weather or 3 gallons for every 5 square feet
  • 2” in hot weather or 6 gallons for every 5 square feet
  • Water early in the day
  •   Use trench or drip methods, not overhead sprinklers
  •   Decrease watering in August to hasten ripening tomatoes

Start Tomatoes, Seed or Store

Sometimes, starting tomatoes from seed is just not practical. Or maybe you aren’t happy with your seedling growth. Depending on your situation, you might just want to buy starts that can be planted directly into the garden. I was at a large home improvement store the other day, and the tomato selection was amazing! They had tomato starts in 6” pots for less than $4.00 and tomato plants in gallon pots for less than $18.00.

Sure, somebody started these plants from seed, but they are totally ready to plant. “No muss, no fuss” as my grandma used to say!

If you want to learn more about how to start a vegetable garden, go here to read the post.