How to Transplant Tomatoes (and How Deep to Plant Them for Stronger Roots)

It’s time to transplant your tomato seedlings outdoors. But how deep should you plant them? And does it really make a difference?

The answer depends on your soil, climate, and the size of your plants.

In this guide, we’ll walk you through exactly how to transplant tomatoes step-by-step, how deep to plant them for stronger roots, and when deep planting works best (and when it doesn’t).

We all get anxious to get those tomatoes planted because gardeners know outdoors is where they’ll thrive. But if you don’t get the timing right, you can set yourself back. Timing matters just as much as technique.

Before transplanting tomatoes into your garden, make sure:

• Soil temperature is at least 60ºF

• Nighttime temperatures stay consistently above 50ºF

• All danger of frost has passed

Tomatoes are highly temperature-sensitive. Planting too early in cold soil can stunt growth, no matter how perfectly you transplant them.

Before moving plants outdoors, make sure to:

• Prepare your soil

• Harden off your seedlings

Now that your soil is ready and the plants have been hardened off, you’re ready to transplant. 

Follow this simple process:

1. Water seedlings well before transplanting

2. Choose a cloudy day or transplant in the evening to reduce heat stress

3. Remove lower leaves from the bottom of the plant (You can do this a few days before to allow the plant to heal.)

4. Dig a hole or trench (depending on method)

5. Water the soil thoroughly

6. Place the plant and backfill with soil

7. Water deeply immediately after planting

8. Add support while plants are small

Unlike transplanting onions and strawberries, where planting depth is critical, tomatoes are much more adaptable and even benefit from deeper planting.

So, how deep is deep enough? 

At a minimum, plant tomatoes at the same depth they were already growing. But tomatoes can be planted much deeper than most plants.

Most gardeners plant tomatoes:

• Up to the first set of true leaves, or

• With ⅔ of the stem buried

If you are transplanting seedlings that still have the cotyledons, remove them and plant deeper to the first true leaves.

If your plant has already been potted up and is well established, planting to the first set of leaves is usually sufficient.

After planting, remove any leaves that touch the soil to help prevent disease.

Talk to avid tomato gardeners, and you’ll hear reasons for why they do what they do from “That’s the way my grandma always did it” to “I saw this experiment on YouTube.” However, these are the top reasons why tomatoes are planted deep.

Tomato plants, like other solanaceous crops, can develop roots along their stems. These are called adventitious roots. 

While most plants grow roots strictly from the original seed root (the radicle), tomatoes have the ability to sprout new roots from non-root tissue, such as the stem or leaves.

You may have seen these white root nodules form under high-moisture conditions or when the plant is stressed. 

By burying part of the stem, you encourage the plant to grow a larger root system.

By planting deeper, the root system reaches moisture deeper in the soil during dry spells. In some soils, moisture levels remain more consistent deeper down. 

More roots mean more surface area to absorb essential minerals from the earth. A vigorous root system easily absorbing nutrients leads to stronger growth and higher yields. 

A deeper root base anchors the plant, preventing it from being blown over or toppling from the weight of fruit. (Although you still want to have a sturdy trellis to keep the branches off the ground.) 

There are two basic ways that gardeners bury their tomato stems. One is the deep-hole method, and the other is a shallower trench in which the plant is laid sideways.

Both methods involve burying a significant portion of the stem—up to two-thirds of the plant—to maximize the area where new roots can grow. 

In both cases, remove the lower branches that would otherwise be in the soil.

This is the standard method used if you have loose, well-draining soil and your seedlings are of a manageable height. If you have a weak stem or leggy stem, planting it deep will give it more support.

The Process: 

• First, remove ⅓ to ⅔ of the lower leaves. 

• Dig a hole deep enough to bury the stem up to the first remaining set of leaves. 

• Place the plant in the hole and fill it in with soil.

This method, like many gardening techniques, has its enthusiasts. Some gardeners find that this method works really well for them, while others say it results in shallow roots. 

The Process: 

• Dig a shallow trench about 6 inches deep 

• Lay the plant on its side in the trench

• Gently curve the top of the plant upward so the leaves are above ground. Be careful not to break the stem. 

• Bury the stem, leaving the top exposed

When using this method, plan the spacing and determine where you want the plant to grow up. One option is to have a group of tomatoes centered in a ring and extending outward. Then you can water and apply fertilizer to the middle.

You don’t necessarily want to plant a tomato at the bottom of a pot. When transplanting into a container, check the depth. Give the plant room to grow its roots downward. Depending on the pot size, this may mean planting only to the depth at which the plant was already growing, or slightly deeper.

If your soil is colder than 60ºF deeper down, you will be better off with a trenching method or even just planting at the depth at which it was already growing. 

When planting in hard or compacted soil, it can be better to plant at the growing level or use the trench method. The roots won’t be able to go deeper, so they’ll need to spread.

Tomatoes behave differently depending on where they are planted. They’re a vining plant that wants to take up as much space as possible.

In garden beds:

Deep planting works well in loose soil

Roots can expand downward and outward

In containers:

Depth is limited

Prioritize leaving space below the root ball

Avoid over-burying if it restricts root expansion

Watering

Water deeply right after planting to settle the soil around the roots. 

Fertilizing

Use a balanced fertilizer, but avoid overfeeding immediately after transplanting.

Support

Place your stakes or tomato cages now to prevent root disturbance later.

Mulching

Wait until the soil is warm, then add mulch to retain moisture and regulate the temperature.

This picture shows a tomato plant we dug up after a few days. The part of the stem that was buried has sprouted new adventitious roots.

It’s normal for tomato plants to pause growth after transplanting. They will first try to establish their roots before they put out new growth. Here are a few things to keep in mind:

• Plants may look droopy

• Growth is slow for a few days

Once the plant has had a few days to reestablish itself, growth will be vigorous. Deeply planted plants can take longer to start putting out new growth. This is one reason to make sure you’re fertilizing your tomatoes with the right nutrients at the right time.

Give your plants room to grow. Containers and raised beds need to have at least 12 inches for roots to expand.

Make sure to pinch off the leaves on the part of the stem you are burying to prevent rot and disease.

• Planting deeply really matters when you are potting up. 

• The difference between tomatoes potted up and those left in their smaller pots is huge. Planting the seedlings deep and giving them more space for root growth results in larger, healthier plants.

• In our garden, we haven’t noticed a difference between the trenching method and deep planting.

• Our method is to dig our hole, fill it with water, let it drain, and then plant the tomato up to the first set of leaves. But we have already potted up at least once.

Transplanting tomatoes is simple. But how you plant them can make a big difference.

You can plant tomatoes at the same depth they were growing, or you can bury part of the stem to encourage a larger root system.