How To Grow Tomatoes From Seed

Tomatoes are a popular food to grow in your vegetable garden and they’re very easy to grow from seeds. The tomato plants can be grown in containers, buckets, hanging baskets, or in the ground in a sunny, warm location.

The varieties of tomatoes are almost endless and run the gamut from Tiny Tim cherry tomatoes that are about the size of a dime to heirloom Beefsteaks that can be the size of a dinner plate and weigh 2-pounds.

Tomatoes also come in a rainbow of colors: red, yellow, orange, pink, green, burgundy, purple, blue, striped, and black. Each color produces a slightly different flavor, but all are delicious.

Select seeds from your favorite varieties and use these guidelines for growing tomatoes from seeds to transplanting to the garden.

Seed Choice

Select seeds from plants that are hardy for your growing climate. If you live in a northern climate that has a short summer, select short-season tomato varieties. 

These varieties will be ready to harvest 50-60 days after the seeds have been planted. Allow 100 days from seed to harvest for all other tomato seed choices.

Tomato seeds are small, and a seed packet will typically hold about 20 seeds. Seeds are cost-effective and are cheaper than starting with plants.

Determinate or Indeterminate

Tomatoes will either be a determinate or indeterminate variety. 

Determinate varieties will ripen their fruits all at the same time. Roma and Rutgers are both determinate varieties and are ideal for growing canning tomatoes. If you want to preserve the produce through canning, freezing, or dehydrating, then select a determinate variety.

Indeterminate tomatoes will produce throughout the summer. Big Boy, Better Girl, and Beefsteaks are plant varieties that will produce slicing tomatoes throughout the summer.

The information of the seed packets will tell you the number of days needed from seed time to harvest time and if the tomato will be determinate or indeterminate.

Growing Medium

Tomato seeds need loose, loamy soil for germination. Loam is soil made with three main soil types: sand, silt, and clay soil

Make sure the growing medium you select to start the seeds in is sterile. Soil from the garden is not sterile and may contain pathogens that will destroy the seeds before germinating.

Starting mixes that contain peat moss, coconut coir, and/or perlite will be lightweight and prevent compaction so the tiny roots of the seedling can grow easily.

Most growing mediums will also contain plant food, so the seedling will have plenty of nourishment until it’s time for transplanting.

Seedling Containers

Any container that can hold soil can be used as a container for seed-starting. However, bio-degradable containers will cause less stress to the plant roots and prevent them from breaking.

Bio-degradable containers come in several sizes and are planted directly into the soil when the seedling is ready to be transplanted.

Some gardeners start their seeds in seed trays for convenience, then transplant the seedlings into bio-degradable cups when they are 2-3 inches tall. The seedlings will remain in the bio-degradable cups until it’s time to place them in their final growing location.

Commercial bio-degradable planting cups are made from peat moss, cow manure, and other organic material that will break down in the soil. You can also create your own DIY planting cups from newspaper or cardboard tubes.

Whatever containers you decide to use to start the tomato seeds, ensure they have sufficient drainage holes in the bottom. If the water does not drain out quickly and the soil remains overly wet, the tiny seeds will rot, and/or the seedlings will develop a disease called ‘damping off’.

Planting The Seeds

Start the tomato seeds indoors in late winter 6-8 weeks before the last predicted frost date.

Fill the containers with growing medium, leaving a little space at the top.

Poke a hole in the center of the growing medium that is 1/4-inch deep. A pencil is just the right size for making the seed-planting hole.

Place one seed in each hole. The seeds are tiny, so using tweezers can help you pick them up.

Scratch a little of the growing medium over the seed and water gently, so the seed is not disturbed.

Keep the soil moist at all times during the germination process. Plastic wrap placed over a seed tray will help retain moisture and create a greenhouse environment for the seeds. Remove the plastic wrap as soon as the first seed germinates.

Warm Location

The seeds will need a warm location to germinate after they have been planted. Sunshine is not important at this stage but warmth is vital.

If you use plastic wrap over the top of the seed tray/containers, that will help keep the growing medium warm. Placing the seed containers on a heating pad or mat will warm the growing medium from the bottom and radiate upwards towards the seeds. Set the heating pad on low.

A warm room near a sunny window will also help warm the seeds so they will germinate.

Several commercial germination containers are available to help you get seeds off to a good start. They will include a heating mat and dome cover that will help keep the moisture and heat level consistent for the seeds. These are helpful but not a must-have item when starting seeds indoors.

Cotyledons

The first leaves that will emerge from the growing medium are called cotyledons. They are part of the embryo within the seed and they supply food to the baby plant coming out during seed germination. Cotyledons contain stored nutrients that are supplied to the seedling during germination.

Cotyledons are not true leaves and they will turn yellow and drop off the seedling when all their stored nutrients have been used up. By the time the cotyledons drop off, the first set of true leaves will have developed on the seedling and the tiny plant will be able to take up nutrients through its’ roots from the growing medium.

Full Sun Location

When the cotyledons appear, it’s time to move the tomato seedlings to a sunny location. Start slowly and increase the sun exposure a little each day to prevent the seedlings from getting sunburned.

Start by placing the seed tray/containers in a sunny location for 2 hours the first day, then increasing the time by an hour daily until the seedlings are in full sun every day. Be sure to keep the soil moist as the direct sun will quickly dry it out.

Soil Preparation

As the seedlings grow and adjust to full sun exposure, it’s a good time to prepare the soil for transplanting time. The seedlings will need loose, well-draining soil and plenty of nutrients.

Prepare the soil in an outdoor garden by working it to the depth of 18-inches. If using a raised bed garden or containers, they should be 18-inches deep to allow plenty of room for the roots to grow.

After working the soil to loosen it, add 2-inches of compost, sprinkle Epsom salt on top, and lightly work them into the soil. Compost is rich in nutrients and improves the soil structure. Epsom salts promote root development and deep growth, plus it helps prevent blossom end rot in the ripening tomatoes.

For raised beds and containers, mix in compost and Epsom salts too. A little Epsom salts goes a long way and a 12-18 inch container only needs 2 tablespoons of Epsom salts. A layer of compost should still be 2-inches deep.

Water the prepared planting site thoroughly and let it sit for at least 2 days before transplanting the seedlings.

Time To Transplant

Wait until the spring weather has been above 70 degrees F (21C) for 3 days before transplanting the seedlings. This will allow the soil to warm up and the seedlings won’t suffer from transplant shock. 

Don’t be in a hurry to get the seedlings outdoors, tomatoes are warm-season vegetables and will not grow until the soil and air temperature are above 70F (21C).

The seedlings must be hardened off before they are transplanted into their final home. This will take one week and it helps the seedlings transition from a protected indoor environment to an unpredictable life outdoors.

Select a sheltered outdoor location where the seedlings will be in full sun but not exposed to wind or rain. 

Take the seedling out to this location each morning after sunrise and bring them back indoors before sunset for 5 days. On the 6th and 7th days let the seedlings remain outside overnight as long as the temperature is above 50 degrees F (10C).

On the 8th day, it’s time to transplant the seedlings.

Trench Planting

Tomato plants will develop roots everywhere the stem comes into contact with the soil. The more roots, the more nutrients and moisture the plant will be able to access. 

A planting method called trench planting is very effective for growing strong healthy plants that produce an abundant harvest of fresh tomatoes. Trench planting can be used for every tomato variety.

Create a 2-inch deep trench in the prepared soil. The length of the trench should be the length from the bottom of the bio-degradable container till the bottom of the second set of true leaves on the seedling. This is usually around 4-6 inches.

Pinch off the bottom leaf set from the seedling. Place the bio-degradable container (or the seedling’s root ball) at one end of the trench and lay the seedling on its’ side in the trench. 

Cover the stem with a handful of compost and finish back-filling the trench with soil. Leave only the top leaves of the seedling above the soil.

Water thoroughly. The seedling will develop roots all along the stem. Space plants 2-feet apart to give them plenty of room to grow and promote good airflow between them.

Trench planting can be done in containers and raised beds. Start the trench near the edge of the container and work towards the center so the top of the seedling will be in the center. Plant 1 tomato seedling per 12-18 inch container.

Mulch

Tomato plants need consistent soil moisture and a layer of organic mulch will help the soil retain moisture. Apply a 2-inch layer of straw, pine needles, shredded newspaper, etc., around each seedling but don’t allow the mulch to touch the plant stem. 

As the mulch decomposes it will improve soil structure and fertility. A second application of mulch may be needed in mid-summer.

Rough mulch, like shredded tree bark, helps keep pests away from plants. Creeping, crawling garden pests, like slugs and snails, will not cross over rough mulch. The jagged edges of the mulch will cut their soft undersides and they will dehydrate.

Water And Food

The soil around tomato plants must be kept consistently moist. Allowing the soil to dry out or flood can result in the tomatoes developing diseases like cat-facing or blossom end rot. 

Tomato plants will take up a lot of water and should be watered deeply once a week. Twice a week during times of extended drought and hot summer temperatures.

The compost in the soil will keep the plants well-fed until they begin to bloom; then, they will need a boost of nutrition. When the first bloom appears, start feeding the plants once a month with a balanced fertilizer. 

Side dress the plants with compost, well-rotted cow manure, blood meal, bone meal, or fish emulsion. Commercial organic fertilizers formulated for tomato plants are balanced for plant growth, root development, and fruit production.

Pinch Off Suckers

As the tomato plant grows, it will develop suckers. These are side shoots that grow along the stem and will suck all the nutrients and energy out of the plant if they are not pinched off.

Suckers will develop at junctions between the branch and the stem. Pinch or snip them off as soon as they appear so they won’t rob the plant of nutrients.

All suckers that develop below the first set of blooms on the tomato plant should be removed. Care must be taken when removing the suckers that develop above the first set of blooms because they look like a fruit-producing stem at first.

The top of the plant can also be pinched out to keep it at a shorter height and some of the side branches can be removed to keep the plant a more manageable size and allow sunshine to reach into the middle of the plant.

Indeterminate tomato plants will need to have the suckers pinched off all summer since the plant will grow all summer. Keeping the plant pruned will also enable you to see pests or diseases before they become a problem.

Harvest Time

Tomatoes can be harvested at any stage of development. Many people enjoy fried green tomatoes or green tomato pickles, but most enjoy the flavor of a vine-ripened tomato.

Growing your own tomatoes from seeds allows you to grow your favorites and harvest them any time you want. The seeds are cheap, the plants are easy to grow, and the resulting fruits are delicious.