How to Grow Tomatoes From Seed in 6 Easy Steps

It’s pretty easy and convenient to pick up a pack of tomato seedlings from your local garden center and plug them into the soil. So you might wonder, what are the advantages of starting these veggies from seed?

A vertical picture showing small peat seed starting pots containing young seedlings set on a red rustic surface. To the center and bottom of the frame is green and white text.

The first reason that comes to mind is that starting your own tomatoes from seed at home is a good way to save money, leaving room in your gardening budget for other things.

You can typically buy a packet of about 20 seeds for the price of one seedling.

But the real motivating factor for me and many other gardeners is that starting tomato seeds at home opens up a dizzying selection of varieties for us to choose from – including less common cultivars we’re unlikely to find as transplants at our local plant nurseries.

So, whether you’re looking for a juicy, jumbo, sweet slicer or a tiny, tart cherry, there’s an incredible array of colors, shapes, ripening styles, culinary uses, and flavors to choose from when you start your tomatoes from seed.

A close up of hands holding a black wire basket full of freshly harvested tomatoes of various shapes, sizes, and colors.

Best of all, growing tomato starts really isn’t that hard!

And if you follow just a handful of smart steps that I’ve outlined below, you’ll keep your starts happy and healthy – providing a bumper crop of succulent homegrown tomatoes that are practically guaranteed to taste far better than anything you could buy from your local supermarket.

A close up top down picture of a variety of freshly harvested tomatoes in a variety of shapes, sizes, and colors, some sliced in half and others whole.

Below you’ll find a step by step tutorial for growing these warm weather veggies from seed. But first, I’ll let you know what kind of essential (and optional) supplies you’ll need for this gardening project.

Here’s an overview of what I’ll cover:

Gather Your Supplies

Before you dive in, first things first. In preparation for growing your own tomatoes at home from seed, you’ll need to gather some supplies.

Some of these are necessities, such as the seeds, starting mix or soil, containers, and a spray bottle.

A top down picture of some gardening supplies needed to start vegetable seeds, including pots, soil, a misting bottle, and plant markers set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

Supplies like plant markers, a widger, and a germination station are highly recommended, but there are many options for you to choose from for these, including some DIY possibilities.

There are also a couple of items on this supply list – grow lights and heat mats – that may be luxury bonus items, or may be required, depending on your setup.

Alright, let’s go over the list of what you’ll need, why you need it, and where you can source these items. Ready?

Tomato Seeds

If you’re growing tomatoes from seed at home, you’ll probably want to take advantage of your increased options and grow some varieties that you wouldn’t be able to buy as transplants at your local nursery.

A top down close up picture of a large harvest of various different types of tomato in an array of colors, shapes, and sizes, set on a gray background.

Seed catalogs contain a huge selection of varieties including short season, long season, determinate and indeterminate, cherry, grape, plum, cocktail, beefsteak, paste, heirloom, open-pollinated, hybrid, potato leaf, red, green, yellow, orange, indigo, purple, black, white, and even striped tomatoes.

Whew! Get my point? There are a lot of options out there!

A top down close up picture of a variety of seed packets set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

If you could use some help sorting through the multitudinous options, we’ve got you covered. Feel free to consult our articles for helpful recommendations detailing the advantages of some of the best heirloom cultivars, our favorite hybrid varieties, and the types best suited to canning.

But if you’re not in the mood for decision-making (I know how it is, we all have our moments) and want just one single recommendation, I’ve got one for you.

I suggest one of my favorite heirloom cultivars, the gorgeous ‘Cherokee Purple.’ This is a beefsteak style tomato with pretty, purplish-red skin that stays green around the stem.

A close up of a large 'Cherokee Purple' tomato with red skin that is green around the stem, on a soft focus background.

The large fruits can weigh up to 1 pound each, and have dense, juicy flesh. Providing a change from the typical red varieties, the flesh of this one is dark, with seeds surrounded by green gel.

I confess – when I cut one of these up, I become mesmerized by its colors.

A close up of a sliced 'Cherokee Purple' tomato, surrounded by herbs and set on a wooden surface.

‘Cherokee Purple’

The flavor of this heirloom is sweet and somewhat smoky, ready to add brightness and an intriguing depth to your summer meals.

If ‘Cherokee Purple’ tempts both your taste buds and your love of gardening, you can find packs of certified organic seeds available at Eden Brothers.

And if you’re wondering how many plants to grow, I recommend starting at least six of each variety – the number of cells in a typical starter tray.

If you were to only plant one tomato seed and it doesn’t germinate, you’ll be disappointed and wonder what it was you did wrong, while it could just be that the individual seed was not viable.

With seeds, we’re all about maximizing our options!

A top down close up picture of a black plastic seed starting tray with four cells, containing rich potting soil and tiny shoots just emerging, set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

Some varieties have a lower germination rate – and seed sellers don’t always print these germination rates on seed packets, so you won’t always know what to expect in terms of germination.

Planting a few extras will help you make up for any losses, particularly with types known for having lower rates of successful germination.

And by the way, if you have some old packs of tomato seeds sitting around and are wondering if they’re still usable, check the date on the packet. If stored correctly, in a dry, dark, and cool location, they will remain viable for five years after harvest.

Starting Mix

To sow your seeds, you can use either potting soil or a soilless starting mix – just check your packet to make sure your soil or starting mix is sterile.

A close up of a white bowl containing rich dark potting soil, set on a wooden surface with biodegradable seed starting pots in the background in soft focus.
Photo by Kristina Hicks-Hamblin.

Regular garden soil that has not been sterilized can compromise the health of your young tomato plants, potentially introducing harmful pathogens, such as those that cause damping off.

If this condition occurs, you’ll notice the stems of your starts browning just above the soil line. The stems will shrivel, and the young plants will collapse and die.

You can read more about protecting your baby tomatoes from damping off in this article, just remember that starting out with sterile potting media is your first line of defense. (And the next is to make sure you do not overwater – but I’ll get to that shortly.)

While sterile potting soil mixes are commercially available, the lightweight media in soilless seed starting mixes enables tender roots and shoots to emerge, and makes transplanting of seedlings easier.

I like to use a soilless potting mix myself – but I always look for those that incorporate the more environmentally sound coconut coir instead of peat moss.

A close up of the packaging of Tank's- Pro Lite Seeding and Potting Mix, in a plastic bag.

Tank’s Pro-Lite Seeding & Potting Mix 16 Quart Bag

Tank’s Pro-Lite Seeding and Potting Mix is one such soilless starting mix, and it’s available from Arbico Organics.

A close up of the packaging of an eco friendly coconut coir seed starting mix compressed into a brick.

Coconut Coir Seed Starting Mix – Makes 8 Quarts

You can also find an organic coconut coir seed starting mix in a convenient, space saving block from Burpee. You just need to add water and the block will expand to 8 quarts, ready for use.

According to an article published by the University of Maryland Extension Home and Garden Information Center, most starting mixes contain enough fertilizer to feed the tomatoes up until time you transplant them into the garden, so you shouldn’t need to apply additional fertilizer.

Starter Trays

You have many different options when it comes to what type of containers to use as starter trays.

You can purchase plastic or biodegradable trays that are specifically intended for growing starts.

A close up of a variety of seedlings in different types of trays and biodegradable pots on a white background.

Or you can repurpose egg cartons, toilet paper rolls, paper or plastic cups, or nearly any other shallow container that will hold your potting mix.

Whatever type of container you use to start your seedlings, make sure it provides good drainage – if your tomatoes’ roots stay too wet, they will be more susceptible to disease.

Photo by Kristina Hicks-Hamblin.

Also make sure the containers are not too big. For tomatoes, it’s best to start with a smaller container and transplant to a larger container when you need to, as the excess soil might stay too wet.

DIY Seed Trays

I tried the DIY egg carton and toilet paper roll methods years ago, and while this creative reuse scores points for the environment, these aren’t my favorite starter tray alternatives.

Cardboard egg cartons may work for smaller starts, but tomatoes will outgrow their shallow cells very quickly.

A close up of homemade seed starter pots from toilet paper rolls containing small green sprouts on a soft focus background.

And the year I tried using toilet paper rolls as seed cups, they started falling apart well before the tomatoes were ready to transplant. I can’t really give a hearty recommendation to either of these options.

You can get creative and find other containers to start your tomato seeds in, but if you want to hedge your bets, your best option may be to purchase seed trays intended for this purpose.

Plastic Seed Trays

When choosing your seed trays, make sure your pick works well for your climate.

In my arid climate, biodegradable trays and pots simply don’t biodegrade – and, yes, I found this out the hard way. Now I stick with plastic trays, which have the bonus of preventing my starts from drying out too quickly between waterings.

A close up of two hands holding black plastic seedling trays containing flowering plants.

6 Cell Seed Starter Trays in Packs of 10

If plastic seems like the best option for you too, these 6-celled trays are an excellent gardening supply for growing starts. Each cell is 1.5 inches square by 2 3/4 inches deep – a good size for your newborn plants.

You can find them in packs of 10 trays at Burpee.

Reusing Plastic Seed Trays

If you’re wondering if you can reuse plastic seed trays and pots, the answer is yes. Just make sure to thoroughly wash them out with hot, soapy water, rinse thoroughly, and then disinfect them.

I recommend a hydrogen peroxide based disinfectant over chlorine-based household bleach, since chlorine bleach can be problematic.

A close up of plastic seed starter trays being washed in hydrogen peroxide solution in a glass bowl.
Photo by Kristina Hicks-Hamblin.

According to an article published by the Baxter County Master Gardeners, chlorine bleach can damage your garden tools and irritate or burn your skin, inhaling the vapor can aggravate certain medical conditions, and it may prove toxic to your plants if any residue remains. This household cleaner really is not as harmless as we might think, despite its widespread use.

BioSafe Disease Control fungicidal spray is a good alternative to chlorine bleach. It contains hydrogen peroxide so it is safe to use on pots, tools, and other surfaces, and it will kill pathogens that cause plant diseases – including those responsible for damping off – when used as directed.

A close up of the plastic bottle of BioSafe Disease Control RTU on a white background.

BioSafe Disease Control 32 Ounce Spray Bottle

You can find BioSafe Disease Control for purchase in a 32-ounce spray bottle at Arbico Organics.

Biodegradable Seed Trays

If you live in a temperate climate, choosing biodegradable seed trays and pots is a wonderful way to go, since you can plant these directly into the ground or into the next size nursery pot without disturbing your plant’s delicate roots.

A close up top down picture of small green shoots growing in biodegradable pots on a soft focus background.

As far as biodegradable trays and pots go, I highly recommend CowPots™, a more environmentally friendly option than those made from peat moss.

CowPots™ are made from composted cow manure sourced from a Vermont dairy farm – and not only do they have a light environmental footprint since they reuse waste material, once you plant them, they will nourish your plants as they break down.

A close up of biodegradable Cow Pots in a six-cell tray showing the dimensions on a white background.

CowPots™ #3 Six Cell Flat

You can find 6-celled CowPots™ trays in packs of various quantities at Arbico Organics. Each cell in the tray is approximately 3 inches square by 3 inches deep.

Nursery Pots

Tomatoes can grow quickly, so having larger-sized nursery pots on hand for repotting is also a good idea.

A close up of a selection of paper cups filled with soil and seedlings, with wooden plant markers set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

I’ve successfully used both plastic nursery pots and paper cups for this purpose.

And just like the biodegradable seed trays mentioned above, CowPots™ are also available in larger sizes for repotting.

A close up of the dimensions of the Cow Pot biodegradable nursery pots on a white background.

CowPots™ #5 Square

You can find square CowPots™ sized at 5.25 by 3.5 by 5 inches in packs of 60 or 192 pots at Arbico Organics.

Or perhaps plastic pots are more suitable for your needs?

A close up of a selection of black plastic nursery pots with one standing upright and several stacked, on a white background.

Pack of 20 Round Nursery Pots

You can find packs of 10 or 20 plastic nursery pots, measuring 7 inches wide by 6 3/4 inches deep, at Home Depot.

Germination Station

For germination, tomatoes require heat and high humidity – conditions that create a greenhouse effect. In other words, they need a warm and humid germination station.

A close up of two rows of tomatoes growing in a large domed greenhouse with condensation on the walls and a pathway in between the rows.

There are a few options you can choose from to create a humid, warm environment for your tomatoes – and your choices range from the extremely low budget to the serious long-term gardening investment.

Plastic Wrap

If you want to keep your spending low for this project, you can create greenhouse conditions by covering your seed trays with plastic wrap.

A close up of a hand placing plastic cling wrap over a red tray containing soil.

If you decide to go this route, make sure to leave a little extra room between the soil surface and the tops of your seed trays, so your baby tomatoes don’t immediately bump their heads on the plastic as soon as they sprout.

And remember to remove the plastic wrap soon after your sprouts poke their heads up above the soil, to ensure air circulation and reduce the risk of damping off.

Domed Growing Trays

A domed growing tray is a fairly inexpensive option for growing starts, especially if you’re not sure you want to invest in equipment for the long term.

A close up of a black plastic seed starting tray set on a gray surface with a white plastic drip tray and a transparent humidity dome, with a wooden fence in the background. To the bottom right of the frame is a white circular logo with text.

12-cell Growing Tray with Plastic Humidity Dome

These germination stations come with a flat for holding your seed trays, and a plastic dome to retain heat and humidity.

You can find a 12-cell growing tray with a drip tray and clear humidity dome from True Leaf Market.

Terrarium

I grow my starts in a terrarium – a mini greenhouse – placed next to a sunny and warm south-facing window.

A close up of four young plants in plastic pots with further plants in a terrarium in the background in soft focus.
Photo by Kristina Hicks-Hamblin.

My young tomatoes get plenty of warmth and humidity this way – and they are protected from my curious cats.

While I have a couple of repurposed reptile terrariums that I use, my favorite terrarium is a more decorative model.

It has more ventilation and doesn’t stay quite as humid as the reptile terrariums, but I have had no problem germinating and growing tomato starts in it.

A close up of a mini terrarium with biodegradable pots containing small plants inside on a white background.

Lean-To Roof Terrarium – Available from Wayfair

Mine is from Ikea, and a model like this can also double as a display case for succulents when you’re not growing veggies. And you can find it for purchase at Wayfair.

Cold Frame

You don’t have to start your tomatoes indoors – you could start them in a cold frame instead, if your temperatures are right.

This setup works particularly well if you receive a lot of warming sunshine in the spring, but not so well if your spring weather is gloomy and rainy, or too cold.

A vertical picture of a wooden cold frame partly open in the garden outside a wooden shed with a metal roof with trees in soft focus in the background.

A cold frame will work if you can keep the interior conditions between 50 and 95°F, with the best temperature range for germination being between 65 and 85°F.

Set up your cold frame facing full south where it will get direct sunlight, providing your young starts with both light and heat.

A close up of an outdoor wooden cold frame containing salad greens.

You can read about making your cold own frame in our article on some of the best DIY greenhouses and cold frames for your backyard.

Cold frames may come with built-in ventilation, or you can prop them open to ventilate and prevent interior temperatures from getting too hot during the heat of the day.

A close up of an outdoor mini greenhouse or cold frame with a selection of lettuces growing inside on a white background.

Juwel 59″ Vented Cold Frame

If a cold frame seems like the best option for you, you may want to try this 59-inch vented polycarbonate model from Juwel. It’s available from Home Depot.

Greenhouse

If you want the best setup of all for growing your own tomatoes from seed, a greenhouse is the ultimate choice – and will give you the space to start an endless selection of cultivars of your favorite summer veggies.

A close up of a large black tray of young plants growing in a greenhouse on a soft focus background.

If you’re lucky enough to already have a greenhouse as part of your gardening setup, growing your starts in your greenhouse is definitely the way to go, since you can use it to provide the light, heat, and humidity they need.

Just make sure you avoid the most common greenhouse mistakes – read our helpful article on this subject to learn more.

If the idea of setting up a greenhouse has your green thumb twitching, you might consider making a DIY greenhouse out of pallet racking.

A close up of a large greenhouse with a black frame on a white background.

Monticello Greenhouse

Or have a look at this selection of aluminum and polycarbonate Monticello brand greenhouses, available for purchase from Arbico Organics.

Plant Markers

Plant markers are a must have if, like me, you plan to start your own personal mini nursery each spring, growing several different varieties of tomatoes as well as many other types of vegetables and herbs.

Without markers to label them all, how will you keep track of your starts?

A close up of a variety of young plants in black plastic pots labelled with plant markers for sale at a farmer's market.

If you are only starting one variety of tomato and no other types of veggies, you can probably get by without plant markers.

And if you are using something like egg cartons or paper cups to grow in, you could just write the name of your plant and the date directly on the container.

However, using plant markers gives you a clear visual sign of what variety you are growing and the date seeds were sown (excellent items to note in your gardening journal, as well).

A close up of round seedling pots with wooden plant markers stuck into the soil on a white background.

You can make your own plant markers out of used popsicle sticks, or you can buy markers intended specifically for this purpose – made either out of metal, wood, or plastic.

While the wooden ones are biodegradable, the plastic ones have more reuse potential since they don’t break down as quickly, and you can wash off the writing.

A close up of white plastic plant markers on a white background.

Pack of 50 Jump Start 6” Plant Markers

You’ll find a pack of 50 reusable 6-inch plastic markers from Arbico Organics.

Spray Bottle

While you can water your seedlings with a small watering can, jar, teapot, cup, or whatever else is handy, using a spray bottle will give you much greater control over how much irrigation you are providing, and help to prevent overwatering.

In fact, correct watering is such an important aspect of growing tomatoes from seed that I consider a spray bottle to be just as important to have on hand as a good quality starting medium.

A close up of a hand from the left of the frame holding a spray bottle and spraying water onto small shoots growing black plastic trays with a wooden surface in the background.

There are a couple of reasons why watering in this manner is preferred.

According to Barbara Larson, Unit Educator at the University of Illinois Extension, the first is that overly wet potting mix can promote fungal disease. Waterlogged soil may also remain too cool after watering, preventing seed germination and slowing root growth.

You can use a plain plastic spray bottle, or a glass one. If you plan to repurpose an empty household spray bottle, only select one to upcycle that has never contained harsh chemicals, since chemical residues can damage your starts.

A spray bottle designated for watering only is great to have on hand anyway, if you have houseplants that need misting or if you grow microgreens.

A close up of a glass mister bottle with a silver colored top on a soft focus background.

Clear Glass Seedling Mister

I love these seedling misters from Burpee. They produce a gentle mist ideal for watering your delicate shoots and are available in clear glass or green metal.

Widger

When removing your young tomatoes from their trays to transplant, you will need some way to lift them out without pulling them by the stems. A widger is one such tool you can use to perform this task without injuring your baby plants.

Photo by Kristina Hicks-Hamblin.

To use this tool, you stick the widger into the soil and under the roots of the seedling to lift it out of its tray – without damaging its roots.

As a DIY alternative, you could also use a small spoon, a popsicle stick, or a wooden plant marker to leverage your plant out of its growing cell.

A close up of a widger or transplanting tool with a long curved knife and wooden handle set on a gray surface.

Widger, or Transplanting Tool

But if you want to take your gardening game up a notch with a more professional tool, you’ll find a tempered boron steel widger available at Burpee.

Grow Lights

I grow my seedlings next to a couple of very sunny, south-facing windows. These provide plenty of sunlight and warmth for my plants as they grow and mature.

A close up of three green planters containing young plants set on a sunny windowsill in light sunshine.

But not all climates or home situations will allow you to take advantage of free light and heat from the sun. So, if you are facing such challenges, you might want to consider using grow lights.

Grow lights have an additional advantage, even if you do have a nice sunny window:

Since they are placed just a few inches above the growing plants, plants will grow stockier and bushier compared to their growth next to a window.

Grow lights also encourage plants to grow straight up towards the overhead light source instead of leaning.

A close up of tiny young shoots in a pot reaching towards the light of a sunny windowsill on a soft focus background.

Plants grown next to a window often reach sideways towards the sun – a problem that can be remedied by rotating your plants regularly.

But they do tend to grow leggier even with regular rotation, as they reach toward the light.

To learn more about grow lights, have a look at our article on some of the best models available and how to use them.

Heat Mat

A heat mat can help to keep the soil  at the right temperature for germination. Having one of these is particularly useful to gardeners in cold or rainy climates, where you can’t rely on the sun to keep your young plants at the right temperature.

A close up of a tiny seedling with the first true leaves starting to appear with rich, dark soil in soft focus in the background.
Tomato plant with its first set of true leaves.

And do you remember what the right temperature is?

That would be 65-85°F for germination.

According to Barbara Lawson at the University of Illinois Extension, lowering the temperature after the first set of true leaves appear helps to promote shorter and stockier growth with stronger stems.

A close up of a Jump Start heat mat with green text and a power cord, on a white background.

Jump Start Windowsill Heat Mat

If it sounds like you could use a heat mat to help regulate the temperature in your growing operation, the Jump Start Windowsill Heat Mat will warm your plants’ roots 10-20°F higher than the ambient room temperature.

You can find it at Arbico Organics.

6 Steps to Growing Tomato from Seed

Now that you have all your supplies gathered up, you’re almost ready to start your tomatoes.

A close up of four young tomato plants ready to transplant into nursery pots set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

There’s just one more important step to take care of before you get your hands dirty:

Getting the timing right.

1. Know When to Sow

It’s important to know when to start your tomato seeds, in order to plant them out at the best time and get the best harvest.

The best time to transplant these summer veggies is a couple of weeks after your average last frost date.

Planting a couple of weeks after this date helps to provide a little wiggle room in case a freak late frost decides to sweep through your area.

A close up of a small young plant covered in a light frost on a soft focus background.

First, determine the average last frost date for your area.

If you don’t already know it, you can look it up at the Old Farmer’s Almanac. Just type in your zip code and the tool will calculate your average last frost date and display it on the screen. Easy!

Most seed packets recommend starting tomato seeds 4-6 weeks before your last frost date, but they assume you will set out your transplants close to this date. We’re going to be a bit more cautious than that.

If you get started just 4 weeks before your last frost, then your starts should be ready for transplanting 2 weeks after your last frost. Make sense?

So, take your last frost date and count back 4 weeks. This is when you should begin your tomato seed starting project.

Learn more about when’s the best time to sow vegetable seeds indoors and outdoors in this helpful guide.

2. Prepare Trays and Sow Seeds

Now you’re finally ready to get started, so let’s go.

Place some starting mix in your seed trays. Fill each cell loosely, then gently tap the tray to remove any air pockets.

A close up of a six-cell black plastic planting tray set on a wooden surface on a soft focus background.
Photo by Kristina Hicks-Hamblin.

You want the soil to fill in the cells without becoming compacted. Loose soil will allow your plants’ roots to spread out nicely, but compacted soil will not.

Gently smooth the surface of the soil to make it level. Leave 3/4 of an inch of head space at the top of the cells, above the soil line.

Sow Seeds

Shake out some seeds from your seed packet into your hand.

To make up for any that may not germinate, plan to sow 2-3 seeds per cell.

Place one seed on the surface of the soil, and repeat with the others, spacing them out an equal distance from each other.

A close up of a hand from the top of the frame sowing tiny seeds into a 6-cell planting tray set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

Grab a pinch of sterile planting medium and sprinkle it over the seeds – cover them with about 1/4 of an inch of starting mix.

Now, gently pat the surface of the soil to smooth it.

Water Gently

Water your seeds in with your spray bottle, spraying until the soil is moist, but not waterlogged. For me, this means about 4 or 5 squirts.

A hand from the left of the frame using a plastic spray bottle to water a six cell tray containing seeds that have just been sown, set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

When your plants get larger, after repotting, you will want to water more thoroughly, with a small watering can or teapot.

A close up of a plastic tray with six cells and wooden plant markers set on a wooden surface with a seed packet to the left of the frame.
Photo by Kristina Hicks-Hamblin.

Write the name of your variety and the date seeds were sown on as many seed markers as you need, and stick them in the tray along the edge of the cell, away from where you placed your seeds.

3. Move to the Germination Station

Place your seed trays in their warm and humid growing location – your “germination station” – whether this is your greenhouse, cold frame, terrarium, grow dome, or just under some plastic wrap.

If your seed tray is placed next to a warm window, you may not need a heat mat. But if you do need extra heat to maintain the soil in your trays at the recommended 65-85°F, place a heat mat underneath them.

You won’t need to expose your trays to light until the tomatoes sprout. Though some types of seeds require light for germination, tomatoes do not.

Check your trays once or twice a day, and water with your spray bottle when the surface of the soil is dry.

A close up of a tiny seedling just starting to germinate with dark soil in soft focus in the background.
Photo by Kristina Hicks-Hamblin.

Within a week or two, germination will take place. Tiny seedlings will rise out of the soil, perhaps holding the seed cases they just emerged from aloft on one of their seed leaves, or cotyledons.

If you used plastic wrap over your seed trays, remove it now.

Provide Light

Make sure you are ready to provide light to your newly emerged tomatoes – whether it’s sunlight from a bright, southern window or artificial light from a grow light.

If you are using a grow light, place it 2-3 inches above your starts.

When using a window for light, your plants will lean towards the window. To correct for this and get your plants to straighten out, rotate your seed trays every few days.

If your “germination station” is a greenhouse, cold frame, terrarium, or domed tray, you can leave your plants there to grow.

4. Daily Care of Your Seedlings

You will need to care for your young tomatoes every day.

  • Water once or twice a day with your spray bottle when the surface of the soil is dry.
  • When starts are bigger and require more water, switch to a small watering can or teapot.
  • Ventilate your germination station so it doesn’t get too hot. Interior temperatures over 95°F will stunt growth.

Optionally, you can expose your young tomatoes to the breeze of a gentle fan, or gently brush your hands over their leaves a few times a day. The purpose of this is to simulate wind and help strengthen their stems.

Thin Your Starts

If the majority of your seeds germinate and you end up with two or three plants growing in each cell of your tray, you may need to thin them.

A close up of young plants in a plastic tray showing them planted very close together.
Photo by Kristina Hicks-Hamblin.

If your seedlings are getting big and their roots are getting tangled, it’s best to sacrifice some of them and keep only the strongest plant in each cell.

If you will be repotting your seedlings in the next step, you can thin them at the same time.

The safest way to do this to avoid disrupting the roots of your remaining plant is to use a small pair of scissors to snip the stems of the rejects, just above the soil line.

A close up of a hand from the left of the frame holding a pair of scissors snipping off a weaker seedling in order to thin the plants in the small plastic tray.
Photo by Kristina Hicks-Hamblin.

Continue snipping until you have just one strong tomato seedling remaining in each cell.

If seedlings are not overly crowded when you’re ready to repot or transplant into the garden, and all of them look strong and healthy, you should be able to gently remove each of them from the soil for repotting without culling any.

5. Repot and Harden Off

Once your baby tomatoes have at least two or three sets of true leaves, they can be transplanted into larger sized nursery pots – unless you are ready to transplant them directly into the garden or their summer containers.

A close up of a white nursery pot filled with soil to the left of the frame, and to the right is a small two cell tray with transplants set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

Repotting will give your tomatoes more room for root growth.

A close up top down picture of two containers filled with rich potting soil set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

Prepare your nursery pot. Fill it halfway with potting mix. Tap the pot to let the soil settle, but not so much that it becomes compacted.

Repotting from Biodegradable Seed Trays

If you started with a biodegradable tray, use a pair of scissors to cut the cells apart so you have separate pots to plant.

Trim down the rim of each cell so it is level with the soil.

Place a biodegradable tray cell directly into the larger sized pot, being careful not to tear it. Add potting mix so it’s level with the soil of the transplant. Repeat with the rest of your seedlings.

Repotting from Non-Biodegradable Seed Trays

Gently remove tomato seedlings from the tray one at a time with a small spoon or widger. Place the spoon as far down into the cell as possible to avoid damaging the roots.

A close up of a hand from the right of the frame holding a spoon and gently lifting out a young plant from a black plastic tray set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

Pull up with the spoon – your tomato should be freed from its first container!

A close up of a hand from the left of the frame holding the roots of a seedling on a soft focus background.
Photo by Kristina Hicks-Hamblin.

Hold the soil instead of holding the seedling by its stem, which is susceptible to disease if it’s accidentally bruised or damaged.

Bury Your Stem

Now you’re ready to place your tomatoes into their new pots.

Tomatoes are one of the few plants that do well when their stems are buried deeply in the soil. This can introduce rot in other plants, but if you sink part of a tomato’s stem in the soil or bury it, the hairs on the stem will turn into adventitious roots.

A close up of the hairy stems of a tomato plant in a black container on a soft focus background.
Photo by Kristina Hicks-Hamblin.

Remove any lower leaves from the bottom two-thirds of the stem, and make sure the tomato still has at least two sets of leaves above the soil. And leave enough stem free so that there are at least a few inches between the soil and the leaves.

Add more soil until there is only a half an inch or so of head space at the top of the nursery pot, tap the pot gently to settle the soil, then water with your spray bottle or watering can.

If the root ball is still small and stringy, fill your nursery pot with soil and tap to settle the soil, until there is an inch or so of room left at the top.

Poke a hole into the middle of the soil with your finger.

A close up of a hand from the left of the frame making a small hole in the soil of a white container set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

Place the young tomato into the hole, sinking it down as deeply as possible without bending the stem.

A hand from the left of the frame gently burying a seedling in a white container set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

Add soil, filling the hole and the nursery pot. Gently tap the pot on your work surface to settle the soil, until there’s about 1/2 inch of room at the top of the pot.

A close up of a hand from the left of the frame putting soil around a young plant in a white circular container set on a wooden surface.
Photo by Kristina Hicks-Hamblin.

Water your repotted tomato and return it to its germination station, place it next to a sunny southern window, or place it under your grow lights, keeping the light 2-3 inches away from the top of the plant.

As you approach your transplant date, continue with your daily care.

Harden Off

Your next step will be to give your tomatoes a transition period to adjust from their protected life in your home, greenhouse, or cold frame to their new location out in the elements.

Providing this transition period is called “hardening off.”

A close up vertical picture of a young tomato plant in a small pot ready to be transplanted into the garden set on a wooden surface. In the background is soil in soft focus.

Tender transplants are vulnerable to outdoor weather conditions. Providing them with a gradual transition to the outdoors will help them become stronger and more resilient.

As Lois Miklas, Master Gardener Coordinator at Penn State Extension points out, a whole host of changes occur in young plants during this period: leaf surfaces thicken and strengthen, they become less prone to freezing, more food is stored in plant tissues, roots grow more quickly, and stem and leaf growth slows.

These changes make plants more resilient and able to withstand temperature changes, less frequent watering, and breakage from wind gusts.

During the hardening off period, gradually introduce your plants to the outdoors during the day for a few hours at a time, slowly increasing the amount of time they spend outside and the amount of direct sunlight and wind exposure they receive.

Here are some tips for hardening off your plants:

  • Give your plants a 7 to 14-day transition period.
  • Start the hardening off process in a shaded, sheltered location.
  • Gradually increase sun exposure and time outside.
  • Protect plants from wind for the first week.
  • Water plants less frequently during the hardening off period, but do not let them dry out or wilt.
  • Only begin hardening off when outdoor daytime temperatures are above 50°F.
  • Don’t fertilize right before or during this period.

Hardening off your young plants may seem like a lot of work. But it’s work that will pay off with bountiful harvests of fresh, delicious summer tomatoes from vigorous plants.

6. Transplant to the Garden

When is it time to transplant your tomatoes to your garden or pots and containers?

After hardening them off, and preferably 2 weeks after your last frost date.

A close up of a glass soil thermometer monitoring the outdoor temperature in the garden.

Tomatoes need soil temperatures of 60°F or higher for growth, so if your soil isn’t that warm yet, hold off on transplanting them until it is.

You can check your soil temperature with a soil thermometer. Keep in mind that this is not the same thing as the ambient air temperature.

When you’re ready to transplant, water your plants well before their big transition into outdoor soil.

Dig a hole a little larger than the pot from which you are transplanting, and add some worm castings or compost to the soil.

If you used a biodegradable pot, don’t remove the transplant – the pot will go into the ground. Just make sure the rim of the biodegradable pot isn’t sticking up above the ground. Trim it before planting it so the top is level with the potting mix, the same way you did with your biodegradable seed starting trays.

If your tomato is in a plastic pot, squeeze the sides of the pot to loosen it, and tilt the plant sideways to slide it out. Try to avoid pulling the plant out by the stem, and only handle the soil if you can.

A close up of a pair of hands transplanting young plants into dark, rich soil in the garden on a soft focus background.

Plant your tomatoes at least as deep as their seed leaves. Planting more deeply is preferable, and will help your plants develop a strong root system.

If your plants are leggy – which they hopefully won’t be if you followed all of the above instructions, but sometimes it happens – you can lay them sideways in a trench in the soil rather than a hole, with just the top several inches of stem and a couple of sets of leaves remaining above ground.

Go ahead and stake your plants now, so you won’t disturb their roots later.

A close up of a young tomato plant in the garden with a wire cage surrounding it to provide support. To the left of the frame is a garden fork.

Keep your newly relocated plants well-watered for the first couple of weeks after transplanting.

For further guidance on transplanting your tomatoes into the garden, see our complete guide to growing these summer veggies.

Seed You Later, ‘Mater

Nice work, gardener! You are now ready to let your plants grow, and await boatloads of delicious homegrown tomatoes.

A close up of a variety of wooden bowls containing various different tomatoes freshly harvested from the garden set on a wooden surface.

Have you started tomatoes from seed before? Do you have any other tips for success to share? If so, I’d love to hear them, so tell me your thoughts in the comments.

Or if you have previously been unsuccessful at growing tomatoes from seed, perhaps this article helped you troubleshoot what went wrong. Let me know!

Looking for more tomato growing and harvesting information? Be sure to check out some of our other guides next:


Don’t forget to Pin It!

A collage of photos showing tomato seeds and young seedlings growing in peat pots

Photos by Kristina Hicks-Hamblin © Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Originally published January 3, 2016. Last updated April 19, 2020. Product photos via Arbico Organics, Burpee, Eden Brothers, Home Depot, True Leaf Market, and Wayfair. Uncredited photos: Shutterstock. 

About Kristina Hicks-Hamblin

Kristina Hicks-Hamblin lives on a dryland permaculture homestead in the high desert of Utah. Originally from the temperate suburbs of North Carolina, she enjoys discovering ways to meet a climate challenge. She is a Certified Permaculture Designer and a Building Biology Environmental Consultant, and holds a Bachelor of Arts degree in liberal studies from the University of North Carolina at Greensboro. Kristina loves the challenges of dryland gardening and teaching others to use climate compatible gardening techniques, and she strives towards creating gardens where there are as many birds and bees as there are edibles. Kristina considers it a point of pride that she spends more money on seeds each year than she does on clothes.

5 1 vote
Article Rating
Subscribe
Notify of
guest
5 Comments
Oldest
Newest Most Voted
Inline Feedbacks
View all comments
Tom H.
Tom H. (@guest_4846)
11 months ago

I sometimes place large rocks about 6-8 inches away from plants, to not interfere with the roots but to give them more warmth to grow by.

Also, if I do the inverted tomatoes I like to hang them on the south side of the brick house. I have harvested tomatoes as late as November, in Detroit, Michigan that way, because of the heat to the plant during the day and the bricks give off warmth at night for a longer growing season.

Barbara Swingle
Barbara Swingle (@guest_7984)
2 months ago

Way too much info all we need is depth, how many weeks to harvest and where to plant while spread from another plant. Not pages n pages of descriptions

Elizabeth
Elizabeth (@guest_8951)
20 days ago

What a wonderfully detailed article! This step-by-step guide is exactly what I’ve been searching for. Thank you so much for putting so much time and thought into helping beginners like me. My quarantine garden thanks you. 🙂