How to Plant Tomatoes: When, How Deep, Fertilizer, Pots & More (2024)

“Plant them sideways! Put an egg in the hole!” There are seemingly endless opinions and theories about the best way to plant tomatoes. Some are valid tips, but some are unnecessary myths! Read along and learn how to plant tomatoes in your garden (or in pots) to set them up for success.

This post will cover must-know tips including the best time to plant tomatoes outside, what amendments to add in the planting hole (or not), how deep to plant tomatoes, their favorite companion plants, and more. We’ll also explore some common misconceptions about those good ole’ epsom salts and eggshell “hacks”. With these tips, you’ll be growing huge healthy tomato plants in no time!

Related: Looking for ways to support tomatoes? Don’t miss our favorite DIY tomato trellis tutorial. Visit our comprehensive guide on growing tomatoes to get even more in-depth tips from seed to table and beyond.

When to Plant Tomatoes

Tomatoes are warm-season crops that do not tolerate frost, so they can be planted outside in early spring after the last risk of frost has passed. However, tomatoes thrive in warm soil and will grow very slowly if the soil is still too cool. In fact, studies show that planting tomatoes too early can make them more susceptible to nutrient deficiencies!

Therefore, it’s best to wait to plant tomatoes outside until the soil temperature is consistently over 60°F in the daytime if possible. 65 to 70°F is even better! Use a simple soil thermometer or compost thermometer to monitor your garden soil temperature (down in the root zone) before planting.

For example, we typically don’t get frost after March here on the Central Coast of California (zone 9), so we could technically plant tomatoes outside as early as late March. Yet we also have very cool and foggy spring weather, so we find our tomatoes grow best if we wait to plant them once the soil warms up in late April to May. Even then, we’ve had freak cold snaps in early May and had to protect the tomatoes with frost cloth.

INDOOR TIPS: Did you start your own tomato seeds indoors? Remember to pot up tomato seedlings to larger containers as they grow, especially if they’re getting big but it’s too early to go outside! Failing to pot up can result in root-bound, stunted tomato plants. Also be sure to properly harden off indoor tomato seedlings before transplanting them outside to prevent shock and damage.

How Deep to Plant Tomatoes

• It’s best to plant tomatoes nice and deep. More roots will grow off the buried portion of the stem, and more roots means more ability to take up nutrients and water – resulting in bigger, healthier, and more productive tomato plants!
• Plant tomatoes so that at least the bottom third or half of the main stem is buried, though you can bury tall or leggy tomato seedlings as deep as two-thirds underground.
• Extra tall tomatoes can also be planted sideways (so you can bury the stem but don’t have to dig such a deep hole), but be careful not to break the main stem in the process.
• Before planting, remove lower branches and leaves that would otherwise be buried or touching the soil. Use garden snips to cut them, or gently pinch them off.
• Water well after planting. In general, tomatoes prefer slow, deep, consistent and less frequent water (compared to small shallow bouts every day) to encourage strong deep roots and more resilient plants. We use drip irrigation for raised beds to water our tomatoes deeply twice per week.
• Don’t forget to add a stake, cage, or other support system after planting – discussed more next.

How Far Apart to Space Tomato Plants

Tomato plant spacing depends on the variety you’re growing, along with the style of pruning, training, or trellising you plan to do. The more you intend to prune your tomato plants, the closer you can space them.

For instance, indeterminate or vining tomato varieties take well to pruning and trellising, and can be spaced as close as 18 to 24 inches apart with moderate pruning. On the other hand, determinate or bush tomato plants are typically not pruned and grow best in large cages, such as our favorite DIY tomato cages. Space determinate tomatoes at least 2 to 3 feet apart.

LEARN MORE: Visit our full guide on tomato plant support ideas to learn more about pruning tomatoes, training methods, and cage or trellis options.

Soil Amendments

A few weeks before spring planting, we amend our raised bed soil with a well-balanced, slow-release organic fertilizer. We dust it evenly over the top, lightly scratch and work it into the soil surface, and then water it in well. We also top off our raised beds with a fresh layer of aged compost each season.

When planting tomatoes, we also add a few things directly in the planting hole:

• Worm castings. We add a small handful of worm castings from our worm compost bin into each planting hole (though you can also buy worm castings online). Worm castings are an incredible form of gentle, natural fertilizer that help the tomato seedlings grow quickly after transplanting. Learn more about thebenefits of worm castings for plantshere.
• Mycorrhizae. These beneficial fungi bind to plant roots and helps them take up more nutrients and water, grow larger and faster, produce more fruit, and also protects the plants from transplant shock and stress. We add a sprinkle of granular mycorrhizae at the time of planting, but you can also water with a water-soluble mycorrhizae after planting too. Learn more about the benefits of mycorrhizae for plants here.
• Crab meal. Last but not least, we also add a sprinkle of slow-release crustacean or crab meal to the planting hole. Crab meal is high in calcium, which is essential for healthy tomato growth and fruit production. A lack of calcium can lead to blossom end rot in tomatoes.
• Application: I like to scratch the crab meal into the planting hole (mixed with the surrounding soil) to reduce direct root contact, whereas the the worm castings and mycorrhizae are good to add right around the root ball.

The truth about epsom salts and eggshells for tomatoes

Time after time, you’ll see recommendations to plant tomatoes with epsom salts or crushed eggshells. Most often, folks claim that these “hacks” help prevent blossom end (BER) in tomatoes. But scientifically-speaking, it’s simply not true!

Blossom end rot is a condition where tomatoes develop a rotten spot on their flower end, and is most often caused by lack of calcium uptake (especially combined with poor or irregular watering practices).

Adding eggshells won’t necessarily hurt your tomatoes, but it does NOT prevent blossom end rot. The calcium in crushed eggshells simply isn’t bio-available enough for the plants to utilize anytime soon. Even more, adding epsom salts (magnesium sulfate) can make blossom end rot worse! According to theUniversity of Hawaii,“the presence of excessive amounts of magnesium, sodium, or potassium in the soil interferes with calcium availability”.

I wrote an entire article dedicated to blossom end rot in tomatoes where you can learn more, including how to treat and prevent it.

Tomato Companion Plants

Don’t forget to give you tomatoes some friends! Planting tomatoes with beneficial companion plants can help attract pollinators, deter pests, and even reduce disease.

The best tomato companion plants include basil, marigolds, peppers, carrots, lettuce, cucumbers, beans, onions, garlic, chives and other herbs like sage, thyme and parsley. Plant any of these together to enjoy a beautiful and biodiverse garden bed!

With their proven ability to repel pesky root-knot nematodes, French marigolds are one of the most notorious and helpful tomato companion plants. Keep in mind that to reap that benefit, the marigold root system should be left in the soil. Meaning, cut the plants out at the end of the season and leave the roots in place.

We always tuck plenty of pretty annual companion flowers around our tomatoes too, like calendula, cosmos, zinnia, bachelor buttons. See our full companion planting chart for other beneficial garden plant pairings and tips.

Planting Tomatoes in a Pot

• Tomatoes grow well in pots, as long as the container is large enough to keep them happy for the season! Tomatoes are big plants with expansive root systems; their growth will be limited by the container they’re in.
• Compact determinate or “bush” tomato varieties are perfect to grow in containers, though you can also grow larger indeterminate (vining) tomatoes in pots too.
• For the best results, I recommend using a 15 to 20 gallon container – such as these fabric grow bags. The ideal pot size for tomatoes is at least 24-inch diameter for indeterminate tomatoes or 18-inch diameter for determinate varieties. You can also grow tomatoes in half wine barrel planters.
• Choose a pot with excellent drainage. Tomatoes like deep consistent moisture, but do not tolerate standing water or soggy roots.
• Fill the pot with quality potting soil made for containers. Potted plants tend to “run out” of nutrients faster than those in the ground or in raised beds, so plan to fertilize potted tomato plants before planting plus once every month or two during the growing season (especially once they start to set fruit).
• Choose a support system (e.g. cage, stakes, trellis) that can fit in or around your chosen pot. Good examples include a sturdy pre-made tomato cage, DIY tomato cages, or several stakes with twine strung between them. Add a stake along the main stem of the tomato too.
  

The Importance of Mulch

After planting, don’t forget to apply a couple inches of mulch on top of the soil. Mulch around the base of your tomatoes, but not in direct contact with the main stalk. Good examples include compost, fine wood chips, or straw.

Mulching tomato plants offers a number of benefits: it helps keep the soil evenly moist, reducing your need to water as frequently while simultaneously reducing the risk of blossom end rot. Mulch also insulates and protects the roots against temperature extremes, including both both hot and cold. Last but not least, it suppresses weeds!

And that sums up the best practices on how to plant tomatoes. I hope this guide gave you plenty of useful pointers, and helps you grow some stellar tomatoes this season. Let us know if you have ay questions in the comments. Also please leave a review or star rating below if you found this post to be valuable. Thank you so much for tuning in today, and happy growing!

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