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The Right Time to Thin Tomato Seedling: A Practical Guide

Most of the Tomato seed you germinate can become a full plant and benefit you with its yield. But for that, you need to know when to thin Tomato seedlings.

Generally, Tomato seedlings are thinned when the plant sets two pairs of true leaves and attains a height of 3 to 4 inches. Instead of uprooting the seedling, use a thin pruning shear to cut off the seedling from its base. 

Thinning in Tomatoes has more to do with plant health and vigor, so follow along to learn about the same.

Do You Need To Thin Tomato Seedlings?

Growing the Tomato plants begins by starting the seeds indoors to give the plant a head start as the last frost ends. 

Generally, for every cultivar of Tomatoes like Cherry, Big Beef or Beefsteak, Celebrity or Early Girl, we sow several seeds close together in a single tray. Clusters of Tomatoes sprout in a tight square, which results in the struggle among the seedlings for nutrients, space, and sunlight.

Moreover, due to the constricted space, seedlings fail to develop the root and stem essential to establish themselves after transplanting, thus requiring thinning.

Thinning is the process of removing the weaker or excess seedlings to facilitate the remaining ones with plenty of room for healthy growth. 

Further, thinning the crowded seed tray helps with proper air circulation preventing mold growth. 

When To Thin Tomato Seedlings?

Under optimal conditions, Tomato seedlings send the root, shoot within a week of sowing, and keep growing. 

When the Tomatoes develop their first set of true leaves, the seedlings would be big enough to struggle for their existence. That’s when thinning is necessary. 

Generally, thining in Tomatoes is done when the seedling is about 7 to 10 cm ( 3 to 4 inches) in about 15-10 days. Thinning at this time ensures the availability of enough sunlight, water, and space for sturdy root growth.
pencil thick stem of seedling
Another indication to thin your Tomato seedlings would be the pencil thickness of the stem.

As time pass by, uprooting the seedlings would be more difficult due to the deeper root establishment, and the chance of damaging the surrounding seedlings is high.

How to Thin Tomato Seedlings?

Now that we know the perks of thinning the Tomato seedling, let’s take the right step.  

  • Start by sterilizing your tweezer with rubbing alcohol to prevent contamination in the seedlings.
  • Carefully observe the seed tray for unwanted leggy Tomato seedlings that appears weak and undergrown.
  • Pull out the unwanted seedlings, ensuring not to disturb and harm.
    healthy ones. Using a tweezer may help you reach the bottom of the seedlings.
Thinning of tomato seedlings
Thinning allows seedlings a good space to grow.
  • Avoid uprooting the seedling as it may damage the delicate roots of Tomato at the seedling stages. Rather, cut the stem off the base. 

What to Do After Thining Tomato Seedlings?

After thinning the seedling, you must space the remaining properly in a separate container or the ground for proper root and foliar growth. 

Moreover, gardeners usually discard the thinned seedlings, as most are incompatible for future growth.

Also, because we snip the plantlet without the roots, transplanting them would give no positive result. 

However, if you uproot one other than the leggy Tomato seedlings, you may transplant them in a pot or container and enjoy some juicy fruit. 

  • Prepare a pot with a well-draining potting mix and some vermicompost, maintaining the pH at 6-7. 
  • To grow the transplant in the garden, make sure to till the soil to make them fluffy. 
  • Dig a hole 4-5 inches deep and 18-24 inches apart for the plant.
  • Now, add a fist full of vermicompost in the hole and plant the seedling over it. Vermicompost is an instant food for your Tomato seedling that help them establish their roots. 
  • Water the transplant thoroughly and daily in the morning until the plants adjust to their new home and produce new leaves. You may need to water the plant twice if the temperature is above 70°F.

Do not worry if your plantlet appears droopy immediately after transplanting. They should be fine once they get used to the new environment.

Pro Tip: Transplant the Tomato seedling only in the evening or early in the morning to prevent heat stress causing the plant to wilt. 

From Editorial Team

Remove the First Set of Flowers!

Pinch the first set of flowers to help the plant spend energy developing the root system and plant structure for prolonged rather than initial fruiting.

Also, as the plant increases in height, remove the bottom leaves to promote linear growth.