How To Grow Tomatoes From Seed & When To Start

Growing tomatoes from seed can be challenging. But once you know how, it really isn’t that difficult. In this post I’ll show you exactly when and how to plant your tomato seeds so you’ll always have strong and healthy seedlings.

There are many benefits that come with growing tomatoes from seed, and it’s straightforward once you get the hang of it.

All you need are some basic supplies and a bit of know-how to get your tomato seedlings off to a good start.

Below I’ll share step-by-step instructions for planting and germinating them, plus essential seedling care tips.

Growing Tomatoes From Seed

Before we dive into the step by step instructions for how to grow tomatoes from seed, first let’s talk about choosing which ones to plant, the best methods to use to start them, and how long it will take.

Types Of Tomato Seeds To Plant

The sheer number of options for the types of tomato seeds to plant can be overwhelming.

But there are a couple of ways to classify them to make it easier to choose what is right for you. Here are just a few of the most popular:

• Paste – If you’re looking for ones that are great for cooking, then try this type. Pompeii or San Marzano are a few examples.

• Slicing – The big meaty fruits are delicious raw, and perfect for sandwiches and salads. Try Brandywine, Mortgage Lifters, or Beefsteak.

• Cherry – These are good for quick snacking, and are generally very prolific. A few examples are Sweet 100, Garden Candy, Sun Gold, or Baby Boomers.

Recommended Tomato Seed Starting Methods

In warm climates, tomato seeds can be planted directly in the garden. But for most of us, starting them indoors is the best method to use.

They require a long, warm season to set fruit. So giving them a head start inside is a good way to ensure you’ll be able to enjoy a bigger crop before frost.

How Long To Grow Tomatoes From Seed To Harvest?

There are so many different types of tomatoes that the range of time from seed to harvest is very broad. It can be anywhere from 60-100 days or longer.

Smaller ones or hybrids bred to produce earlier may be ready in as little as 60-80 days after germination.

Indeterminate types, or ones that bear larger fruits can take anywhere from 70 to more than 100 days from seed to harvest.

Related Post: How To Tell Determinate vs Indeterminate Tomatoes

Planting Tomato Seeds

In order to get a jumpstart on their long maturity dates, planting your tomato seeds with care is important.

With a bit of planning and the right tools it’s easier than you might think, but timing is everything.

When To Start Tomato Seeds

In colder climates, the ideal time to start tomato seeds indoors is between 6-8 weeks before the last frost date in your gardening zone (for example, I’m in z4b here in MN).

If you live somewhere warm and would like to direct sow them, wait until it’s consistently above 45°F at night. That’s usually about 2 weeks after your last frost in late winter or early spring.

How To Plant & Grow Tomato Seeds Step-By-Step

Once you know how to do it, planting tomato seeds is really simple. Get your supplies ready beforehand to make the process quick and easy.

Supplies Needed:

• Tomato seeds
• Covered trays
• Seed starting soil or pellets
• Water
• Hand trowel
• Grow light
• Heat mat (recommended)
• Soil thermometer (optional)
• Moisture meter (optional)

Step 1: Prepare the soil – If you’re using pellets, pre-moisten them before placing them in the trays. Otherwise use your hand trowel to fill each cell with a damp soil mix.

Step 2: Decide how many seeds to plant – If you have a new packet, one per cell is fine. For older tomato seeds, plant 2-3 in each to compensate for lower germination rates.

Step 3: Plant the seeds – They’re small, so plant them no deeper than ¼”. You can either make a small hole and drop them in, or lay them on top and gently press them down into the soil.

Step 4: Cover the seeds – Completely cover the tomato seeds, and gently press the soil down so it comes in good contact with them. Take care not to push so hard that you compact it though.

Step 5: Water the soil – They’ll need to stay evenly moist in order to germinate. Water until the soil is damp, but not saturated.

It’s gentler to do so from the bottom by pouring it into the tray rather than over the top, which may displace the tiny tomato seeds. A moisture gauge can help you monitor the levels more easily.

Step 6: Cover the trays – A plastic dome lid or large bag (as long as there’s enough headroom for seedling growth) will help hold in the moisture and heat during germination.

Step 7: Keep them warm – Choose a warm location, or place them on a heat mat to keep them in the ideal range of 65-85°F. A soil thermometer will help you maintain the perfect temperature.

Tomato Seeds Germination Time

Most tomato seeds germinate between 7-14 days. Your exact time will depend on the variety you planted and the environment they are in. The specific range can usually be found on the seed packet

Cool temps and inconsistent moisture can slow down or even prevent germination. Keeping the soil evenly moist but never soggy, as well as adding bottom heat will speed things up.

Related Post: How To Make Sturdy DIY Tomato Cages

What Do Tomato Seedlings Look Like?

There are two stages to tomato seedlings, and they both look very different.

The seed leaves will come first. These two small leaves are long and oval shaped, tapering to a point at the end.

All of the ones that form after the first two are called the “true leaves”, and they look like tiny tomato leaves.

How To Germinate Tomato Seeds Faster

If you’d like to speed up germination, you’ll need to provide optimal conditions. Warmth, humidity, and air circulation are key.

Setting them on a heating mat to keep the soil at a warm 70-85°F will help tomato seeds germinate faster.

Covering them with a humidity dome will also help to keep them warm, and prevents them from drying out too quickly.

Soaking your seeds may speed things up too. Give it a try by placing them in tepid water for 12-24 hours before planting. 

Related Post: How To Prune Tomatoes For Maximum Production

How To Care For Tomato Seedlings

Planting and germinating tomato seeds is the easy part, but caring for the seedlings is where most people struggle.

In order to be successful, you must provide the right amount of light, water, and fertilizer to get them strong and healthy. You can read my full seedling care guide, but here are some quick tips…

Light

As soon as the seedlings pop up, they need 14-16 hours of light every day, or they’ll get leggy very quickly. Unfortunately, even the sunniest window is not enough.

Use a grow light positioned 3-4 inches above them at all times, and set it on a timer to make it easy to give them the right amount.

Water

Keep the soil evenly moist at all times, but never puddled or soggy. As they get taller you may need to check them every day. A moisture gauge is handy for helping you get it right.

Fertilizer

After 3-4 weeks you can begin adding an organic half-strength, balanced fertilizer once a week. Compost tea or fish emulsion are good options.

Air Circulation

When half of your tomato seeds have germinated, begin removing the humidity dome by opening it a little more each day.

It’s also a good idea to run an oscillating fan on low nearby to simulate wind and strengthen seedlings. This will also provide plenty of airflow so they won’t mold.

Thinning

If you planted more than one tomato seed per hole, thin the seedlings to one per cell when they’re 3-4 inches tall.

Choose the healthiest ones, and snip the others at soil level with clean micro-pruners or precision shears. Dividing them is risky, even minor stem or root damage can kill them.

Potting Up

When your tomato seedlings have developed three sets of true leaves, pot them into larger 3-4” plastic or plantable pots. Bury them deeper, up to the first set of true leaves, to encourage stronger roots.

Related Post: How To Grow Tomatoes In Pots

When To Transplant Tomato Seedlings Into The Garden

You can transplant tomato seedlings into the garden when nighttime temperatures are above 45°F, or the soil is a warm 70°F.

Before you do so, it’s crucial to harden them off so they can adjust to the outside elements. Otherwise they may not survive the transition.

Learn exactly how to care for tomato plants in your garden here.

FAQs

Here I’ve answered some of the most commonly asked questions about growing tomatoes from seed. If yours isn’t on the list, please add it to the comment section below.

How long does it take to grow tomatoes by seed?

How long it takes to grow tomatoes by seed will depend on the specific variety you have. They’ll germinate between 7-14 days, and can begin producing fruit anywhere from 60 and 100 days after that.

What month do you start tomato seeds?

The exact month you start tomato seeds depends on your climate. In colder zones, you should plant them indoors 6-8 weeks before your last frost date, or direct sow them 2-3 weeks after frost in warmer areas.

How many tomato seeds do you plant per hole?

How many tomato seeds you plant per hole depends on their age. Newer ones are more likely to germinate, so one per hole is fine. They lose viability as they age, so for older ones, I recommend planting 2-3 for best results.

How deep should I plant tomato seeds?

You should only plant tomato seeds between ⅛-¼” deep, since they are not very large.

Do tomato seeds need light to germinate?

No, tomato seeds do not need light to germinate. But they do need warmth and humidity.

Should I soak my tomato seeds before planting?

You don’t need to soak your tomato seeds before planting, but it won’t hurt them. It may be a way to speed up the germination rate.

Now that you have all the steps, supplies, and tips on starting tomatoes from seed, you’ll be able to tackle it with confidence. Watching those seedlings get bigger is so rewarding!

If you’re tired of struggling to grow seeds and robust seedlings for your garden, then you need a to take my Seed Starting Course. This fun online course will guide you through everything you need to know step by step, and at your own pace. Sign up and get started right now!

Otherwise, if you’re just looking for a quick refresher to get going fast, then my Staring Seeds Indoors eBook is what you need.

More About Growing Seeds

• How To Grow Tomatillos From Seed & When To Plant
• How To Grow Onions From Seed & When To Start
• How To Grow Broccoli From Seed
• When To Start Seeds Indoors (The Perfect Guideline)

More About Tomatoes

• Quick & Easy Pickled Green Tomatoes Recipe
• Sun Dried Cherry Tomatoes: An Easy Homemade Recipe
• Tomatoes Not Turning Red? Try These 5 Tricks…
• How To Can Cherry Tomatoes

Share your tips for planting and growing tomatoes from seed in the comments below.