When and How to Transplant Tomato Seedlings

Knowing how to transplant tomato seedlings is a key step in growing strong, productive tomato plants. Whether you’re starting seeds indoors or buying transplants, knowing exactly when and how to move tomatoes to the garden can mean the difference between a thriving crop and stunted growth.

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In this guide, we’ll walk through the signs that your seedlings are ready, how to prepare them and your garden, and the step-by-step process to transplant them successfully—with tips to avoid common mistakes and reduce transplant shock.

Why Transplanting Tomato Seedlings Is Important

Transplanting tomato seedlings is an essential step to the growing process. It is one step that might occur more than once during the growing season. Each time you transplant your tomato seedlings it helps develop a stronger root system.

The first instance in which you will need to transplant your tomatoes is if you’ve started them from seed. This prevents overcrowding in seed trays or allows the tomato more soil to grow if you’ve used a soil blocker to make soil blocks.

Our preferred method to starting tomato seeds is to use soil blocks. If you would like to learn more check out our in depth soil blocking how to guide. We prefer it because it helps prevent root balls from forming if you don’t transplant your seedlings fast enough. Also check out our how to start indoor seedlings guide for more info on starting from seeds.

One of the main reasons to transplant tomato seedlings is to encourage faster, healthier growth. Tomatoes are fast growers and will quickly outgrow their initial starting location. That’s why transplanting into larger pots or “potting up” is an important step. It allows the tomato seedling to grow a larger root system which will create a healthier plant.

Other benefits to transplanting tomato seedlings into larger pots is it allows for better spacing for airflow and access to light from grow lights. As well as if you have leggy seedling you can transplant them deep into larger pots and correct the issue. Read more on leggy seedlings and proper thinning in this article.

When to Transplant Tomato Seedlings Outdoors

There are several factors for when you can transplant your tomato seedlings outdoors.

• Wait to transplant tomato seedlings until they have 2 or 3 sets of true leaves. True leaves are the leaves that form after the initial 2 leaves when the seed sprouts.
• Your seedlings should be 6 to 10 inches tall and have strong sturdy stems and root system.
• Nighttime temperatures in our area stay above 10°C (50°F). For us in zone 5b this is around the May long weekend (about the third weekend of May).
• Wait until after all risk of frost in your region has past. This might vary year to year and it’s a good idea to double check the forecast before transplanting.

Ideal Conditions for Transplanting Tomato seedlings

More important than air temperature is the soil temperature. Soil temperature of 15°C (60°F) or higher will give your tomatoes the best start.

The time of day and weather conditions when you transplant tomato seedlings are also important. It is best to transplant on a dry or overcast day that is not too hot. If it’s a hot and sunny day the best time to transplant your tomatoes is in the evening when it has started to cool down. This will allow the seedlings time to acclimate to the new environment overnight.

Pick a suitable location for for your tomatoes. They require 6-8 hours of sunlight per day. If they receive less than 6 hours of sun their growth and your harvest will be stunted.

Soil conditions is another factor when transplanting. Tomatoes require well draining highly fertile soil with a soil PH of 6.0-6.8. A mix of compost, aged manure, and worm castings is ideal. Pre-fertilizing the soil before transplanting with a balanced slow release fertilizer or tomato specific fertilizer will help give your tomato seedlings the best start.

Hardening Off Tomato Seedlings

Hardening off tomato seedlings is a crucial step in the transplanting process. Without hardening off your seedlings you run the risk of them experiencing transplant shock. They could get:

• Sunburned leaves: Young tender tomato leaves not used to direct sunlight can become bleached, scorched, or curled.
• Wilt and Droop: Sudden change to growing conditions like strong wind, direct sun, and hotter or colder temperatures can cause the to wilt dramatically. Sometimes within a matter of a few hours.
• Stunted growth: Shocked tomato seedlings can stop growing for days or even weeks while they recover which will result in a delayed fruit production and your harvest.
• Greater risk of disease: Weak tomato seedlings are more susceptible to pest and fungal diseases.
• Increase in plant loss: In severe cases of transplant shock the seedlings could die within 24-48 hours after transplanting.

To harden off seedlings properly, start about 7-10 days before transplanting with a small increment of exposure to the outdoors. Start with 1-2 hours of outdoor time in a sheltered spot. Bring the tomato seedlings in at night especially if the temperature is going to drop below 10°C (50°F).

Increase the exposure time and direct sunlight daily but avoid days with strong wind, heavy rain, and not during the hottest part of the day initially. By the end of the week your seedling will be strong enough to be transplanted and avoid transplant shock.

How to Prepare the Soil or Containers for Transplanting

Choose a sunny location in your garden to transplant your tomato seedlings. If you’re using a container make sure it is at least a 5 gallons in size like these grow bags. Amend the soil with compost or aged manure and you can also pre-fertilize using a generic slow release fertilizer.

Dig holes deep enough to bury 2/3 of the seedlings stem. Doing this will allow roots to grow all along the part of the tomato plants stem that’s buried. Spacing your tomato plants 18-24 inches apart to maintain good airflow and prevent diseases.

For more information on preparing your garden beds read this post all about how to prep your garden beds for spring.

Step-by-Step Guide: How to Transplant Tomato Seedlings

Before transplanting tomato seedlings into their final growing place there are some steps that will give them the best start in their new home.

1. Water seedlings well 1–2 hours before transplanting. Giving the seedling a fresh drink of water will help loosen up the soil that they’re currently growing in and allow for the roots start growing into their new surroundings.
2. Dig planting holes deep enough for part of the stem to be buried. Tomatoes will grow roots all along the part of the stem that is buried. Ideally you only want to have a small part of the stem and a few leaves above the soil surface after transplanting.
3. Gently remove seedlings, keeping root balls intact. With the soil being wet after watering, this step is a lot easier. Make sure to not break any roots in this process or your seedlings could be stunted.
4. Place seedlings in holes, pinch off lower leaves, and bury the stem. Any leaves close to the new soil surface need to be removed. Leaving the leaves could result in disease or pests harming your seedlings.
5. Back fill with soil and press gently around the base. After your tomato seedlings is in the hole you’ve dug for it, gently back fill the soil pressing gently around the base. While doing this you can make sure the tomato stem is perpendicular to the ground so it’s not growing on a slant.
6. Water deeply to settle the roots. To help promote new growth, water your tomato seedlings deeply. If using a garden hose, run the water on each seedling for 10-15 seconds at the base of each plant. Make sure the leave are not getting wet in the process.
7. Mulch the soil to retain moisture. To help keep the soil moist and reduce the need for frequent watering mulch the soil with straw, wood chips, or grass clippings. Learn more about mulching in our Mulching Garden Beds: Best Practices & Common Mistakes post.

Common Transplanting Mistakes to Avoid

Transplanting Tomato Seedlings Too Soon

The most important thing to avoid when you transplant tomato seedlings is planting them too early. It can be a hard thing, especially for beginners, but you need to wait until all risk of frost in your region has past. If you plant your tomatoes too soon and there is a frost, it is likely that your tomato plants will die.

Skipping the Hardening Off Process

Although not as catastrophic as planting too soon, skipping the hardening off process is also very detrimental and should be avoided. Not hardening off your tomatoes could result in transplant shock, delayed growth, delayed harvest, and potentially the death of your plants.

Disturbing Roots or Planting Too Shallow

This mistake won’t necessarily kill your tomato plant but it will definitely stunt its growth. If roots are broken during the transplanting process new growth could be delayed by a week or two while the plant heals. Planting too shallow will not allow for new roots develop along the part of the stem that is buried. This results in fewer roots, less nutrient uptake, and poorer overall growth.

Over-watering Immediately After Transplanting

It is important to water deeply after transplanting but roots also need to breath. Watering too much and too frequently can result in:

• Root Rot: Saturated soil can cut of oxygen to the roots causing them to suffocate. Fungal diseases are more likely to spread in these conditions.
• Poor Root Development: With so much water root growth will be stunted because the roots won’t need to grow and reach deeper into the soil to access water.
• Delayed Recovery: Transplanted tomato seedlings are already stressed and watering too much will cause a delay in them adjusting to their new growing conditions. It can cause the leaves to yellow, wilt, and delay overall growth.

Post-Transplant Care for Tomato Plants

After your have successfully transplanted your tomato seedlings there are a few maintenance tasks that are still required.

Water Tomatoes Regularly

Tomatoes require 1-2 inches of water a week. This is a combination of water from all sources including rain and manual watering. Mulching your tomatoes will help keep the soil moist between watering.

Install Supports For Tomatoes

Tomatoes, especially indeterminate tomatoes, require a trellis to climb up as they grow. Pictured above is a simple trellis we use for our tomatoes. It’s built using T posts and 2×4 lumber. With this system, when we transplant tomato seedlings, we tie a string to the 2×4 at the top and bury the string under the root ball of the plant. This anchors the string in the ground and allows something for the tomato to climb.

This could easily be built out of spare wood or tree branches. A tomato trellis for indeterminate tomatoes should be at lease 6 feet tall.

Monitor Your Transplants For Shock

Check for signs of transplant shock including wilting or yellowing of the leaves. Either could be a sign of over-watering or under-watering. To tell if the soil is dry or wet stick your finger in the soil about 2 inches deep. If the soil is moist at that depth, watering is not required.

Fertilize Your Tomatoes

Apply diluted water soluble organic fertilizer after 1–2 weeks if needed.

Helpful Articles to Help You Grow Tomatoes Better:

• How To Grow Tomatoes From Seed To Harvest.
• What’s Wrong With My Tomatoes?!
• A Simple Way To Save Tomato Seeds
• Tomatoes: A Weed or Invasive Species?

FAQ About Transplanting Tomato Seedlings

Q: Can I transplant tomatoes on a hot day?

A: It’s best to transplant on a cloudy day or in the late afternoon to reduce shock.

Q: How deep should I plant tomato seedlings?

A: Deep enough to bury part of the stem—tomatoes grow roots along buried stems.

Q: How soon will tomatoes start growing again after transplanting?

A: Typically within 3–5 days once they adjust to their new environment.

Q: Can I transplant leggy tomato seedlings?

A: Yes! In fact, burying leggy stems helps stabilize the plant and develop more roots.

Conclusion:

Transplanting tomato seedlings doesn’t have to be intimidating. With the right timing, preparation, and care, your young plants will quickly establish themselves and grow into healthy, productive tomato vines. This small investment in time now will pay off big later in juicy, homegrown tomatoes all summer long.

We hope you enjoyed this growing guide. If you did make sure you check out the other growing guides, seed saving guides and our recipes. We are growing our website with more articles all the time, and we invite you to grow with us. Whether you’re a seasoned gardener or just starting out, growing tomatoes can be an enriching experience. If you have any questions or want to share your tomato-growing journey, feel free to leave a comment below. Happy gardening!