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Save money by learning to grow tomatoes from seeds indoors instead of buying pre-grown tomato plants from your local garden center.

Tip: Did you know that tomato plants love eggshells and bananas for fertilizer?! Learn more about how to use eggshells in your garden as well as banana peels for fertilizer!

Types Of Tomatoes To Grow From Seed

There are many varieties of tomatoes. If you are growing tomatoes for fresh eating during the summer I suggest planting:

  • Cherry Tomatoes
  • Beefsteak Tomatoes
  • Cherokee Purple Tomatoes

For tomato varieties that are best for canning or preserving, I suggest planting:

  • Roma VF
  • Amish Paste
  • San Marzano

How to Grow Tomatoes From Seed Indoors

What is the difference between Indeterminate Tomatoes and Determinate?

The terms “indeterminate” and “determinate” refer to the growth habit of tomato plants.

Indeterminate tomato plants continue to grow and produce fruit throughout the growing season until they are killed by frost or disease at the end of the growing season. These plants tend to be tall, and vine-like, and require staking or other support to keep them upright. Indeterminate tomatoes are also known as “vining” tomatoes.

Determinate tomato plants, on the other hand, grow to a certain height (usually around 3-4 feet) and then stop growing. They produce all of their fruit at once, typically within a 2-3 week period, and then the plant begins to decline. Determinate varieties tend to be bushy and compact and do not require as much support as indeterminate tomatoes.

Ensure to refer to your seed packet or seed catalog to see what type of tomato plant you are growing!

How to Grow Tomatoes From Seed Indoors

How to Grow Tomatoes Indoors | Indoor Seed Starting Setup

I suggest investing a little bit of money into a budget-friendly indoor seed starting setup that includes a grow light, seedling heat mat, some seed trays, and a sturdy shelf. We purchased our metal seed starting shelf at Home Depot and we only wish we would have bought it sooner!

If you have never heard of LED lights for starting seeds, I highly recommend them. They provide a sunny spot for the homegrown tomatoes during the cooler temperature when the natural sunlight isn’t sufficient enough. The bright light replicates the sun of the summer or early spring, encouraging the seedlings to grow into strong healthy tomato plants.

LED Shop Lights

These bright LED lights connect together and fit perfectly on your seed starting shelf.

Since many tomato varieties require a fairly long growing season, giving your heirloom seeds a head start will allow you to grow an abundance of tomatoes even in colder climates.

When To Plant Tomato Seeds

Take a look at the back of your seed packet. You should see when the ideal planting date would be for that variety before your last frost date. Generally, it is late winter, about 8-10 weeks before your last frost date.

Since tomatoes are warm-season crops that grow slowly, I like to sow seeds at the end of February for zone 4b with our peppers, but you can start your seeds right up to early April.

How to Grow Tomatoes From Seed Indoors

How To Plant Tomato Seeds

Step 1: In a large container mix your seed-starting mix with warm water until the soil feels moist to the touch but not soaking wet. Transfer the damp soil to your starter trays or small pots banging the tray on a hard surface a few times to remove any air pockets.

Step 2: A quick rule for seed planting depth is twice as deep as a seed is wide. So plant your tomato seeds about a 1/4″ – 1/2″ deep and gently cover the seed with soil. To plant them your can either place the seed on the soil surface and push it down or make a small hole before dropping the seed in.

Step 3: This step is optional, but to help keep the soil moist during the germination period, add a light layer of vermiculite on top of the soil in the seed trays.

Step 4: For best results, cover your tray with a humidity dome or plastic wrap to keep in the moisture and place on a heat source such as a fairly warm spot in your home or on seedling heat mats. If the area is too cool your germination rate will be slower.

How to Grow Tomatoes From Seed Indoors

Tomato Seed Germination Time

To grow tomatoes from seed, it can take up to just over a week to reach their germination rate. Depending on your tomato variety, most tomato seeds will germinate between 5-10 days. The warmer the area, the faster the germination period.

Keep an eye on your seedlings for sprouting, ensuring they are kept in ideal conditions. If you find that your seeds are not germinating, try moving them to a warmer spot, or they are not viable seeds.

When your seeds germinate you will see a tiny plant pop out of the organic matter with its first leaves. These are called “seed leaves.” Once you can identify the seed leaves, remove the seedling from the heating mat and place them under a grow light in an area that provides enough light for them to grow strong.

How to Grow Tomatoes From Seed Indoors

Caring For Young Tomato Plants

Once the seeds start to grow, they will form their second set of leaves. These are called “true leaves” these leaves are what you will probably recognize from a typical tomato plant.

As the plant grows, if the seedling doesn’t get enough light it will become “leggy” this can be identified if the seedlings grow long thin stems and start to reach toward the nearest light source. To avoid this, place the tomato seedlings under a grow light, about 4 inches high, or in a spot that gets full sun.

If you notice your seedlings have become leggy, I have a post that help you save your leggy seedlings.

Watering Your Tomato Seedlings

To maintain a thriving tomato seeding, ensure they are watered regularly. The best way to water seedlings is from the bottom. Do this by placing your seedling tray in a shallow container or sink and let the roots soak up the water from the bottom. Give them enough water that the seedling tray has a bit of weight to it and the top of the soil is moist to the touch.

How to Grow Tomatoes From Seed Indoors

Proper Lighting For Tomato Seedlings

If your tomato seedlings don’t get enough light, they will start to grow leggy and reach for the nearest window. So, in order to keep them growing thick and compact, it’s best to use a grow light. Hang a grow light a few inches above the seedlings as soon as they germinate and keep it on for 14-16 hours per day. for optimal conditions.

How To Fertilize Tomato Plants

Once the plants have established their first set of true leaves, it’s time to start fertilizing. Avoid a full-strength dose at the beginning. Use a weak dose at first, and slowly increase the strength as the plants grow. I suggest using this organic fish fertilizer, by adding it to your watering once a week. I started using this organic fertilizer last year, and it was the best year for our garden!

Tip: Did you know that tomato plants love eggshells and bananas for fertilizer?! Learn more about how to use eggshells in your garden as well as banana peels for fertilizer!

Air Circulation | Grow Tomatoes From Seed

When you are prepping your seeds for germination, a warm, high humidity environment is best. Once your seedlings grow their true leaves, they require a good air circulation to avoid any fungal diseases.

Providing your seedlings with a gentle breeze with a small fan will not only avoid any unwanted fungus, but it will help the seedlings grow strong thick stems! The air from the fan acts as the wind, and it sends a signal to the young plant to start growing thicker and stronger! This helps your tomato plants get ready to be in their permanent home outdoors!

How to Grow Tomatoes From Seed Indoors

Planting Tomato Seedlings In Bigger Pots

Once your tomato plants have outgrown their seedling trays it is time to plant them in bigger pots! You can tell it is time to pot up your tomato plant by the roots. If you can see roots coming from the bottom of the tray, it is time to pot up. Leaving the tomato plants in a container that is too small can stunt their growth, impacting your tomato yield at harvest.

Get a container that is double the size of the seedling cell tray. I like to use recycled nursery pots, you can also use solo cups or old larger containers.

Fill the larger pot with soil and carefully remove the seedling from its old cell. Place the seedling in the pot and cover it with soil. I like to plant the seedling a little bit deeper to encourage stronger steam and root growth. Give the seedling water to help with transplant shock and place it back under the lights.

How to Grow Tomatoes From Seed Indoors

Hardening Off Your Tomato Plants In The Garden

Hardening off seedlings is a critical step in successfully growing seeds indoors, and it’s one that many beginner gardeners miss. It is an essential part to ensure your tomatoes grow into a healthy plant without the added shock of the new outdoor elements. Hardening should take between 7-10 days before planting in the garden.

On a mildly warm day start by placing your tomato plants outside and avoid any direct sunlight. Watch the movement of the sun and make sure they are watered and aren’t wilting from the heat of the sun. If they start to fade, move them to a more shaded area.

Watch the forecast for any extremely hot weather, high winds, or heavy rain. Your seedlings need to slowly adapt to the weather. Start slowly by starting when the weather is close to what their past environment in the house was. It is best to start hardening off your tomato plants in the early hours of the day when the elements are gentler for the plants.

Plan to leave your tomato transplants out for only a few hours during the first few days. Bring them back indoors under their lights after a few hours.

Slowly increase the number of hours they are outside and slowly introduce them to the sun. Repeat these steps for at least a week while slowly exposing them to the sun, wind, rain, etc.

On the final days, it’s time to leave your plants outside overnight. make sure the nighttime temperatures are above 50°F (10°C). Protect the tomato plants by placing them close to a building. I like to keep our plants on our back deck beside the brick, tucked under the roof.

How to Grow Tomatoes From Seed Indoors

Planting Tomato Plants In The Garden

After hardening off, before planting your tomato plants directly into your garden ensure the risk of frost has passed. Most zones are good to plant in late May to early June. (Find out your last frost date here)

Begin by spacing your tomato plants out a foot apart in the garden. Larger varieties may require more spacing. Be sure to check the back of your seed package to see what spacing your variety needs.

Plant the young plants just below the first set of leaves from the roots. This allows them to grow more roots, and allows the original roots to grow stronger. Give them a good water after planting.

TIP: If there is a frost risk AFTER you plant your tomatoes in the garden. Use a blanket, and carefully cover them to protect them from frost. Remove the next day, after the risk of frost, has passed.

How Long Does It Take To Grow Tomatoes From Seed To Harvest?

Depending on the variety of tomato plants you are growing, it can take anywhere from 4-5 months (90-110 days) to grow tomatoes from seed to harvest.

Some grow much quicker than others, most plants will start producing much faster if they are strong and healthy and live in ideal conditions. So give them plenty of heat and sun for the best results.

How to Grow Tomatoes From Seed Indoors

Can You Plant Tomatoes From A Seed In A Tomato From The Grocery Store?

Yes, you can! Some companies spray their produce with a chemical that stunts the growth of any potential seeds in the tomatoes If you would like to grow tomatoes from seeds from a grocery store tomatoes, you will have the best luck with organic varieties.

Do Tomato Seeds Need Light To Grow?

No, tomato seeds do not require light until AFTER they have germinated. All they require is a moist, warm environment to germinate successfully. Be sure to keep an eye on your germinating seeds, as soon as you see the first set of true leaves pop up, place them under a grow light immediately.

What Is The Fastest Way To Grow Tomatoes From Seed?

The fastest way to germinate tomato seeds is to provide them with the most ideal conditions possible. Using a heat mat, moisture, and a humidity dome will encourage your tomato seeds to germinate quickly.

Can You Grow Tomatoes On a Balcony?

Yes! We have grown tomatoes in containers for years and had a lot of success! Ensure you are using a big enough pot or grow bag for the variety you are growing.

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How to Grow Tomatoes From Seed Indoors (19 Easy Tips)



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A community for those looking to take things slower in life. We discuss and share things like gardening, preserving (canning, freezing, dehydrating), homemaking, and homesteading.