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how to grow tomato seeds in a pot

How to Grow Tomatoes From Seed

The Spruce / Kara Riley

There are typically tomato plants for sale at local garden centers. But you can also grow tomatoes from seed.   Because the plants are heat lovers, most gardeners don’t have growing seasons long enough to start tomatoes from seed outdoors. To get around that, tomato seeds are often started indoors. Learn how to plant tomato seeds, care for the seedlings, and ultimately transplant the tomato seedlings outdoors into your garden.

8 Things You Can Do To Get More Tomatoes This Year

What You’ll Need

Equipment / Tools

  • Trowel
  • Gardening gloves
  • Grow lights (optional)
  • Fan (optional)

Materials

  • Tomato seeds
  • Small containers with drainage holes
  • Potting mix
  • Water
  • 3- to 4-inch pots with drainage holes
  • Liquid fertilizer

Instructions

materials for growing tomatoes from seedThe Spruce / Kara Riley

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The Spruce / Kara Riley

Select Your Preferred Tomato Seed

It’s fairly easy and inexpensive to start many tomato varieties from seed, so experiment with the types you like best. Here are some factors to take into consideration:

  • Look for certified organic seed if you prefer organic produce.
  • If you know your area is prone to particular plant diseases, choose a hardy tomato variety.
  • If you want your tomatoes all at once to preserve them, look at determinate varieties. ​Indeterminate types bear over a longer period, with some starting later in the season than others.
  • Note the mature size of the plant. In general, determinate plants tend to be smaller than indeterminate ones. Small plants for containers often have names that include “patio” or “pixie.”

choosing tomato seedsThe Spruce / Kara Riley

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The Spruce / Kara Riley

Prepare the Containers for Planting

It’s often more efficient to dampen the potting mix before you put it in the containers. Add some water, and work it through the soil. Keep adding water until the mix stays compressed in your hand but is not dripping wet. It should break apart when you poke it with your finger.

Then, fill your containers with potting soil. Gently firm the soil, so it’s about an inch from the top.

preparing the containers for plantingThe Spruce / Kara Riley

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The Spruce / Kara Riley

Plant the Tomato Seeds

Make a 1/4-inch furrow in the potting mix. Then, sprinkle two to three seeds into the furrow, and cover them with a sprinkling of potting mix. Gently pat down the mix, so the seeds make good contact with the soil. You can spray the surface with water if it doesn’t feel moist.

At this point, place your containers somewhere warm. Check them daily to make sure the soil is moist—but not wet—and watch for germination. Tomato seed germination typically occurs in about five to 10 days.

planting the seedsThe Spruce / Kara Riley

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The Spruce / Kara Riley

Care for the Tomato Seedlings

Keep your tomato seedlings warm and moist, and provide them with light—preferably grow lights. Rotate the plants if they seem to be leaning in one direction. Once your tomato seedlings have true leaves, it’s time to start feeding them. Any good liquid fertilizer can be used once a week, but dilute it to half the label’s recommended dose.

Tomato stems grow sturdier if they are tossed about by the wind. You can simulate this indoors by putting a fan on your plants for an hour a day or by gently running your hand through them each time you pass.

caring for tomato seedlingsThe Spruce / Kara Riley

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The Spruce / Kara Riley

Pot the Tomato Seedlings

When the seedlings are 2 to 3 inches tall and have a couple sets of true leaves, it’s time to pot them in larger containers. In general, 3- to 4-inch containers are a good size, though you might have to move them to larger pots later if you can’t plant them outdoors.

Fill the new pots with moist potting mix just as you did when you started the seeds. If more than one seed germinated in the same container, you will need to thin the seedlings. Either gently jiggle entangled roots apart, or simply snip off unwanted seedlings at soil level. This ensures that you won’t damage the seedling you want to keep.

Plant each tomato seedling in its new pot a little deeper than it was in its original container. If it’s tall and leggy, you can plant it right up to its top-most leaves. Then, firm the soil gently around the seedling.

transplanting seedlings into a larger containerThe Spruce / Kara Riley

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The Spruce / Kara Riley

Transplant the Seedlings Outdoors

When you’re finally ready to plant your tomatoes in the garden, choose a cool or overcast day. Once again, plant them deeper than they were in their pots, so new roots will form along the buried stem.

You can plant them all the way up to the top couple sets of leaves. This is especially ideal if your plants have gotten too tall indoors, and you want them to become stockier and stronger. If you can’t dig deep enough, you can always plant them sideways in a furrow. The top of the plant will find the sun and grow upright in a few days.

tomatoes planted in the gardenThe Spruce / Kara Riley

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The Spruce / Kara Riley

When to Plant Tomato Seeds Indoors

Tomato seeds usually germinate within 10 days.   The plants also develop quickly, especially if you keep them warm and give them lots of light, so seeds should be started six to eight weeks before you intend to transplant outdoors. For instance, if you plan to transplant outdoors in early May, start your seeds indoors in mid- to late March.Your transplant timing will depend on your last frost date, which is determined by your USDA hardiness zone and that year’s specific weather.

When to Transplant Tomato Seedlings Outdoors

Err on the side of caution when it comes to transplanting outdoors. If you put the plants out too early, frost or a cold spell could easily hinder their growth or kill them. Tomatoes planted a little later in the season will quickly catch up to earlier transplants that have been stunted by cold.

In general, when nighttime temperatures remain steadily above 50 degrees Fahrenheit, it’s safe to begin hardening off your seedlings. Your plants should be several inches tall at this point with some branching. One method is to expose them to the outdoors for gradually increasing stretches each day, starting about seven to 10 days before you intend to transplant them into the garden. After this transition period, they should be ready to live in your garden.

Tips to Care for Tomato Plants

Stake your tomato plants right after you plant them, so you don’t disturb their roots later. Then, give them a good drench of water, and be patient. They should start flowering when the days heat up.

Tomatoes are prone to diseases of both the leaves and the fruits.   The best defense is to keep your plants healthy and strong. Give them regular water, leave room between plants for good air circulation, and check them daily to catch any problems in the early stages.

Finally, it’s easy to get carried away with planting tomato seeds. But note that a family of four can easily feast throughout the summer on just six plants.

Growing tomatoes from seed is a rewarding experience that yields healthy, tasty, and fresh produce. Learn tips for growing tomatoes from seed.

Growing tomatoes from seed: A step-by-step guide

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Why start your own tomato seeds when you can pop into your local nursery and buy ready-to-plant seedlings? The biggest reason is variety! Your local nursery may have a dozen or so varieties of tomatoes, but growing your own tomatoes from seed allows you to choose from thousands of heirloom, hybrid, and open-pollinated varieties available through seed catalogs. Plus, starting your own tomatoes can save money, especially if you have a large garden.

Starting your tomato transplants from seeds is fun and easy.

Growing tomatoes from seed: Types of tomato seeds

When flipping through your favorite seed catalog, you’ll probably notice descriptions like ‘heirloom’ (or sometimes ‘heritage’), ‘open-pollinated’, and ‘hybrid’. Understanding the different types of seeds will help you pick the right tomato varieties for your garden.

It

  • Heirloom – An heirloom tomato is an open-pollinated variety that has been passed down through the generations. The main reason to grow heirloom tomatoes is flavor! The fruits are packed with mouthwatering flavors that are seldom matched by hybrid varieties. Of course, heirlooms offer diversity, too — fruits in an assortment of sizes, shapes, and colors. Popular heirlooms include Cherokee Purple, Brandywine, Pineapple, and Big Rainbow.
  • Open-pollinated – Open-pollinated seed is pollinated by insects, wind, or even gardeners. When the seed is saved you can expect the seeds to come true. The exception to this is when cross-pollination from other varieties has occurred. If you’re growing more than one variety of open-pollinated cucumber or squash, for example, they will likely cross-pollinate. If you only grew one variety, your open-pollinated seeds are safe to save. All heirloom seeds are open-pollinated, but not all open-pollinated varieties are heirlooms. Dwarf Sweet Sue, Dwarf Caitydid, and Glacier are examples of open-pollinated tomatoes.
  • Hybrid – Hybrid seeds are the result of controlled pollination where the pollen of two varieties or species are crossed by plant breeders. These are often listed as ‘F1’ varieties in seed catalogs. Generally, the seed of hybrids cannot be saved as they won’t come ‘true to type’. So, why grow hybrids? Most hybrids offer improved traits, like disease resistance, vigor, higher yields, earlier harvest, and uniform ripening. Sun Gold is a very popular heirloom tomato with golden, cherry-sized fruits.

Choosing the best tomato seeds to grow

Now that we’ve gotten some background on the types of tomatoes seeds, it’s time to crack open those seed catalogs. Be prepared to encounter dozens, if not hundreds, of tempting varieties. To learn more about the many awesome tomato varieties available to grow in your garden, check out Epic Tomatoes, the award-winning book by Craig LeHoullier.

But, with so many varieties to choose from, how do you pare down your list and decide what to grow? Consider these three questions:

How much space do you have?

The growth habits of tomatoes are broken down into two categories: determinate and indeterminate.

  • Determinate varieties are best for small spaces and container gardens. They grow two to three feet tall with fruits that mature around the same time (perfect for canning or sauce!). They also mature earlier than many indeterminate tomato varieties.
  • Indeterminate varieties , also called vining tomatoes, are the big guys. They can grow six to eight feet tall, and continue to grow and fruit until frost. You’ll need to stake or support the vigorous plants. You can grow them in containers, but I’d suggest finding a large pot and supporting them securely with stakes or a trellis.

How long is your season?

As you flip through seed catalogs, notice that tomatoes are categorized by how long they take to mature — early, mid-, and late-season. I find it more helpful to refer to the ‘days to maturity’, which is how many days a variety needs to produce fruit once they are transplanted (not seeded!) in your garden. In short-season or coastal gardens, opt for fast-maturing, early tomatoes, like Moskovich (60 days), Northern Lights (55 days), or Sun Gold (57 days). If you’d like to figure out the length of your growing season, check out this handy calculator on the National Garden Bureau website.

How are you going to use your tomato harvest?

There are so many different types of tomatoes to grow: slicing, cherry, paste, cocktail, and grape, for example. When I’m trying to decide what to grow, I find it helpful to consider how I want to use my harvest. I like to make several batches of sauce, but most of our tomatoes are enjoyed fresh from the garden in sandwiches and salads. Therefore I plant a mixture of types, including those for sauce, some super-sweet cherry or grape varieties, and beefy heirlooms for slicing.

Growing tomatoes from seed allows you to grow a rainbow of colors, flavors, and sizes.

Step-by-step guide to growing tomatoes from seed:

Step 1 – Sow seeds at the right time

Growing tomatoes from seed takes about six to eight weeks from sowing to transplanting. Starting seeds indoors too early results in leggy, overgrown seedlings. I aim to transplant my seedlings into the garden about a week after my last expected spring frost date. Find out the last frost date for your region and count backwards by six to eight weeks. That’s when you should sow your seeds indoors.

Step 2 – Use clean containers

I start a LOT of seeds each spring and want to be able to use my growing space efficiently. Therefore, I sow my seeds in plastic cell packs placed in 1020 trays. They’re reusable and I can cram hundreds of plants under my grow-lights. You can also use plastic pots or recycled clean yogurt containers, milk cartons, and so on.

Plant tomato seeds in a high-quality potting mix in clean containers.

Step 3 – Use a high-quality seed starting mix

Give your tomatoes the right start with a lightweight, well-draining growing medium like Pro-Mix Seed Starting Mix. Moisten the mix before filling pots or cell packs to avoid uneven wetting.

Step 4 – Plant seeds at the right depth

Tomato seeds are fairly small and if you plant them too deeply, you’ll never see them again. Sow them about one-quarter inch deep, covering lightly with moistened potting mix. Label each variety with a plastic or wooden tag and the name written in permanent marker (trust me, you won’t remember which is which if you don’t label them).

Step 5 – Provide plenty of light

Sturdy, healthy seedlings need plenty of light. Too little light results in legginess where the seedlings reach and stretch, eventually flopping over. The ideal place to start seeds is under a grow light, where you control the amount of light. My grow lights are inexpensive, four-foot shop lights hung with chains on a wooden shelf. As the plants grow, I can move my lights up so that they are always just a few inches from the foliage of my tomato plants. I leave the lights turned on for sixteen hours a day, and have a timer that turns them on and off. You can use a sunny window to start tomato seeds, but due to low light conditions in late winter, expect some stretching. If you plan on making seed starting an annual event, consider investing in a grow light, like this fluorescent fixture or a SunBlaster.

Use grow-lights to grow healthy seedlings

Step 6 – Maintain moisture

Overwatering is one of the quickest ways to kill delicate seedlings, so keep an eye on soil moisture. It should be slightly moist, but not soaking wet. Once seeds are sown, use a clear plastic dome or a sheet of plastic wrap overtop of the trays and containers to maintain moisture. Once germination occurs, remove all covers so that air can circulate.

Step 7 – Provide adequate air circulation

As indicated in my previous step, air circulation is important when growing healthy tomato plants. My grow lights are set up in my basement where there isn’t a lot of air circulation. This could lead to fungal issues if I didn’t have a small oscillating fan in the room to move air. Having moving air also toughens up the stems and foliage of the seedlings.

Step 8 – Feed the seedlings

Many potting mixes contain slow-release fertilizer to feed your plants slowly over several weeks. You can supplement these fertilizers with an organic water soluble fertilizer, applied at half the recommend rate every 12 to 14 days. Carefully read and follow all labels on potting mix bags and fertilizer containers.

Step 9 – Harden off tomato seedlings

You’ve reached the last step of growing tomatoes from seed! Once you’ve reached the final spring frost date, it’s time to harden off your tomato seedlings. Hardening off is the process where indoor-grown seedlings are acclimatized to the outdoor garden. Expect this process to take five to seven days (read more about hardening off HERE). Start by putting the seedlings outside in the shade for a few hours. Bring them back indoors that night. Continue to put the seedlings outside, gradually introducing them to more sun each day. They are be ready to be transplanted into the garden or containers within a week.

For more on seed starting and growing tomatoes, check out the following articles:

Last thought: If you enjoy growing your own tomatoes from seed, you may get a kick out of this hilarious book, The $64 dollar tomato.

Are you going to be growing tomatoes from seed for your vegetable garden?

Growing tomatoes from seed is the BEST way to enjoy the thousands of varieties available through seed catalogs. Learn how to pick which tomatoes to grow for your garden and how to grow healthy seedlings.

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Reader Interactions

Comments

Musette says

thanks for the tutorial. Each year I swear I’mo DO IT! Then I get busy. And then I have to go get plants from my local nursery. Your tutorial is a reminder of how easy it is to start from seed! Thanks again!

Niki Jabbour says

Thanks Musette! You can DO IT!! 🙂

Debbie says

You have Sun Gold under the hybrids and it is in fact an F1 but you state it is an heirloom. You might want to change that so as to not confuse anyone.
It is indeed a great cherry tomato and my favourite.

Niki Jabbour says

Hi Debbie, thanks for your comment. Sun Gold is indeed a hybrid but with so many heirlooms I’m not surprised that there could be one also named Sun Gold. Here’s the variety I’m talking about which is the Sun Gold available through most seed companies. – https://www.johnnyseeds.com/vegetables/tomatoes/cherry-tomatoes/sun-gold-f1-tomato-seed-770.html
Either way – it is a spectacular variety! Thanks, Niki

Debbie says

I live in Ontario, have your Year Round Veg Gardening and love it. We used to be able to buy Sun gold (F1) in the garden centres here but no more. I used the last of my precious seed last year and placed an order for some from Halifax Seeds so I feel a kinda kinship to you ha ha. Have a great gardening season.

Dawn says

Should I wait until I see seed sprouting before turning on grow lights?

Niki Jabbour says

Good question! I usually turn them on when I place my seed flats beneath the lights. This is because the lights throw off a bit of heat which can speed up germination. You can wait however if you prefer. – Niki

Brenda McNulty says

My tomato plants are doing really well, in fact they are up to the lights on the shelf, and I still have a month to go until planting time. They have nice sturdy stalks. Should I remove them to a table and place them under some higher lights in the basement? Last year I used different seeds and they did not grow like this.

Niki Jabbour says

Hi Brenda, If you have the option of moving them to a space with higher lights I would do that. Keep an eye on them to make sure they continue to grow well. Different types of tomatoes can grow in different ways. If you grew determinate types last spring they are more stocky. Indeterminate varieties can get tall, quick! 🙂 Hope that helps – good luck. – Niki

Growing tomatoes from seed allows you to enjoy the wonderful heirloom and hybrid varieties available from seed catalogs. Plus, it's easy and cost effective!