Can You Plant Tomato Seeds Directly In The Ground? (3 Tips)


When spring gets closer, we naturally to want to start growing tomatoes as soon as possible. It can be tempting to start seeds early, or to start them outside – but that might not always be a good idea.

So, can you plant tomato seeds directly in the ground?  You can plant tomato seeds directly in the ground if you live in a warm climate with a long growing season.  For colder climates, you should start tomato seeds indoors and transplant the seedlings outdoors later.

Of course, there are plenty of good reasons to start tomato seeds indoors, even if you live in a warm climate.  By planting tomato seeds directly in the ground, you might make things more difficult for yourself and for your tomato plants.

In this article, we’ll take a closer look at what can happen if you start tomato seeds too early or too late. We’ll also discuss why you might want to start tomato seeds indoors.

Let’s begin.

Can You Plant Tomato Seeds Directly In the Ground?

In some cases, you can plant your tomato seeds directly in the ground outside (this is known as direct sowing). However, there are certain conditions to be met.

tomato seedling
You can plant tomato seeds directly in the ground if you live in a warm climate with a long growing season.

For example, your climate should be warm enough with a long season for tomatoes. To be more precise:

You will likely need at least 74 days for the fastest-maturing tomatoes, and 123 days for slow-maturing varieties.

If you are going to plant tomato seeds directly in the ground, there are a few things to keep in mind.

Tomatoes Are A Warm Weather Crop

First, remember that tomatoes are a warm weather crop. In fact, according to the University of New Hampshire Extension, tomatoes are native to the tropics.

Tomatoes cannot tolerate frost, so they are unsuitable for planting before the last frost date in an area. In fact, it is wise to wait until a few weeks after the last spring frost date to transplant tomatoes outside.

frosted leaf
Tomato plants cannot tolerate frost, so wait until a few weeks after last spring frost to plant seeds or transplant seedlings.

The Old Farmer’s Almanac suggests transplanting tomatoes 1 to 4 weeks after your last spring frost date.

You can find the last spring frost date in your area on this page from the Old Farmer’s Almanac.

Direct seeding for tomatoes is no different. Wait until at least a few weeks after the last spring frost date to plant tomato seeds outdoors.

Otherwise, you risk losing your plants to cold before they even really get started!

Planting Tomato Seeds Directly Means A Later Harvest

Also remember that planting directly will lead to a later harvest. When you start tomato seeds directly in the ground, they do not get a “head start” on the growing season.

This can be a big problem in cold climates with a short growing season. In a cold climate, the tomatoes might not be ready to harvest before the first fall frost!

tomato plants
Tomato plants started too late may not produce ripe fruit before the first frost date.

By starting seeds indoors before the last frost date, you give your tomato plants a chance to grow indoors. This extends the growing season by weeks or months, which is critical when the growing season is short.

Starting tomato seeds indoors also guarantees that curious animal pests will not get the chance to eat the seeds before they germinate!

Tomato Plants Do Not Like Temperature Extremes

Finally, keep in mind that both cold and hot temperatures can be a problem for tomato seeds and plants.

thermometer
Tomato plants do not like extreme temperatures – too cold or too hot won’t do.

For example, tomato seeds will only germinate in soil that has a temperature of 50 to 95 degrees Fahrenheit (10 to 35 degrees Celsius).

The ideal soil temperature range for tomato seed germination is 65 to 85 degrees Fahrenheit (18.3 to 44.2 degrees Celsius).

Remember: just because tomatoes are a tropical warm weather crop does not mean they like extreme heat!

In fact, temperatures of 86 degrees Fahrenheit (30 degrees Celsius) or above can prevent flowers from forming and cause improper fruit ripening. Temperatures above 95 degrees Fahrenheit (35 degrees Celsius) stop the plant from growing.

Note: tomato seeds take 6 to 11 days to germinate under the proper conditions (soil temperature, moisture, etc.).  You can learn more about optimal conditions for tomato seed germination here.

What Happens If You Plant Tomatoes Too Early?

If you plant tomatoes too early, then there is a higher risk that the plants will be killed by a frost or freeze (temperatures below 32 degrees Fahrenheit or 0 degrees Celsius).

When you plant tomato seeds too early, then the soil will still be too cold. This can lead to a failure of seeds to germinate.

Even if seeds do germinate, it will be much slower at low temperatures. In fact, according to the University of California, it can take tomato seeds up to 6 weeks to germinate at a soil temperature of 50 degrees Fahrenheit (10 degrees Celsius).

Such slow germination will lead to a delay in the development of your plants.  Starting tomato seeds indoors will help you to avoid this problem.

plug plants
Start seeds indoors to outsmart Mother Nature, avoid spring frost, and extend the growing season.

Of course, you can always use a cloche to keep your tomato seeds and seedlings a little warmer (even if they are planted outside).

A cloche is a covering that protects a plant from cold, wind, and insects, while allowing sunlight through.

This sunlight helps to heat up the air inside the cloche and the soil underneath it.  The greenhouse effect prevents heat from escaping and keeps the tomato plant warmer.

Usually, a cloche is made of plastic.  You can make a cloche out of an ordinary plastic water bottle with the bottom cut out.

water bottles
You can make a cloche by cutting the bottom out of a plastic bottle.

You can even take off the cap on the bottle, so that the opening can act as a vent.  This will give the plant some air on hot days and prevent overheating.

You can learn more about garden cloches in my article here.

What Happens If You Plant Tomatoes Too Late?

If you plant tomato seeds too late, then the summer heat can prevent the seeds from germinating.  Even if the seeds do germinate, the plants may not mature fast enough to produce ripe fruit before the first frost in the fall.

You can find your first frost fall date here.

A frost or freeze will kill tomato plants, so they need to finish growing and producing fruit before the first frost.  Most tomatoes take anywhere from 74 to 123 days to grow from a seed to a mature plant that produces ripe fruit.

Of course, you might want to add 20 to 30 days to that figure. That way, you will have 3 to 4 weeks to harvest tomatoes from your plants.

ripe tomatoes on vine
Tomatoes need at least 74 days to grow from seed to mature fruit.

If you start tomato seeds indoors and transplant them outside later in the season, then the plant will only need 7 to 14 weeks (49 to 98 days) to produce ripe fruit.

Steps To Take If You Direct Sow Tomato Seeds

If you do decide to direct sow your tomato seeds, there are a few important steps that you can take.

Prepare The Soil For Planting

The first order of business is to prepare your soil for planting tomatoes.

  • Choose the right area for planting – Make sure that the spot you select has well-draining soil and gets plenty of sunlight.  Early in the season, you will have to think ahead to avoid a spot that is shaded by the leaves of trees later in the season.
  • Add some compost to your soil – This will improve the soil structure and allow the soil to retain some water without staying soggy.  Compost will also provide nutrients for plants.  In addition, compost will add organic material to attract beneficial soil organisms (such as earthworms and nitrogen-fixing bacteria.)
  • Add fertilizer, if necessaryGet a soil test before adding anything to your soil, to find out if it is really necessary.  Always follow the instructions on the package, since it is possible to over fertilize your plants!
  • Sift your soil – This will remove any rocks, sticks, roots, or other debris that can prevent seeds from growing properly.
  • Wait for warm weather – The soil temperature should consistently be over 50 degrees Fahrenheit (10 degrees Celsius) for tomato seeds to have any chance of germinating.  This will almost certainly be after the last frost date in your area.  The Old Farmer’s Almanac has a tool here, which you can use to look up frost dates.
compost bin
Compost adds nutrients and organic material to soil, and you can make it from yard and kitchen waste.

Plant The Seeds

  • Plant each tomato seed at a depth of 0.25 inches (0.6 centimeters) –  Plant the seeds in a row, about 2 feet (0.6 meters) apart.
  • Install supports – do this early, before the plants grow. That way, you will avoid damaging their roots.  For taller indeterminate tomato varieties, use stakes driven into the ground close to the seeds.  For shorter determinate tomato varieties, use tomato cages with the planted seed in the center of the cage.
  • Leave 4 feet (1.2 meters) between rows – This will allow enough space later in the season for pulling weeds and watering, fertilizing, inspecting, and harvesting.
tomato stakes
Use stakes to support indeterminate tomatoes, or cages for determinate tomatoes.

Take Care Of Your Tomato Plants As They Grow

  • Water your seeds carefully – Too much water will wash away soil and seeds alike.  It might be easier to keep the soil moist by using a spray bottle.  After the seeds germinate and seedlings emerge, you can use a watering can or hose to provide more water.
  • Use twine to tie your tomatoes to the stake as they grow – This support will keep them from falling over or breaking due to the weight of the fruit.  Keeping the plants off the ground will also decrease the chances of diseases (which are found in the soil).
twine
Use twine to tie tomatoes and secure them to their supports.

If you don’t have twine, you can find more ideas for tomato ties in my article here.

Why Should I Start Tomato Seeds Indoors?

When you start tomato seeds indoors, there are several advantages over direct sowing.

You Can Thin Your Seedlings (Plant the Strongest)

One advantage of direct sowing is that you can sow many more seeds than you need.  After germination, you can pick out and transplant only the strongest seedlings that emerge.

tomato seedling
If you start seedlings indoors, you can thin them by choosing only the strongest ones to transplant outside.

This process is known as thinning your seedlings.  Thinning your seedlings ensures that plants do not compete with one another, and also ensures that you have extra plants to avoid falling short.

You can learn more about how to thin seedlings in my article here.

If you were to simply plant seeds outdoors, some of them would fail to germinate and grow.  By then, it might be too late in the season to replace them with new tomato seeds.

You Can Extend the Growing Season

When you start tomato seeds indoors, you can extend the growing season.  This is especially useful in cold areas where winter lingers.

The Old Farmer’s Almanac recommends starting tomato seeds indoors 6 weeks before the last spring frost date, and transplanting seedlings outdoors 2 weeks after the last spring frost date.

By using grow lights, heat mats, and humidity domes, you can start tomato seedlings indoors.  By the time you transplant them outside, they will be well-established.

You can learn more about how to keep seeds warm in my article here.

Tomato seedlings should be transplanted to larger pots when they have their first set of true leaves. Usually, this will occur at a height of 2 to 4 inches (5 to 10 centimeters) tall.

They can be transplanted outdoors 8 weeks after planting from seed. Usually, this will occur at a height of 6 to 10 inches (15 to 25 centimeters) tall.

tomato seedling
Tomato seeds germinate in 6 to 11 days. Move them to bigger containers at 2 to 4 inches tall, and transplant outside 8 weeks after planting the seeds.

Just remember that you will need to harden off your tomato seedlings when transplanting them outdoors.  To harden off your seedlings, expose them to outside conditions gradually over time.

Start off by giving your seedlings a little exposure to the sun, wind, and weather outside.  Over time, slowly give them more exposure to the sun and to the elements so that they can adapt to these conditions.

Eventually, you can move the seedlings into full sunlight and let them fend for themselves (although you still need to water them as they grow!)

You can learn more about how to harden off seedling s in my article here.

Conclusion

It is possible to plant tomato seeds directly in the ground (direct sow) and end up with healthy plants.  However, this is more likely to be successful in a warm climate with a long growing season.

For most people in most climates, I would recommend starting tomato seeds indoors and transplanting them out to the garden later.

This helps you to avoid late spring frosts, and it extends the growing season.  It also ensures that you will have enough healthy transplants to grow as many tomato plants as you want.

I hope you found this article helpful – if so, please share it with someone who will find the information useful.  It’s time to get started with planting your tomato seeds!

You can learn more about everything you need to grow tomatoes in my article here.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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