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Why Are My Tomato Seedlings Turning Yellow? [Easy Fixes]

Tomato seedlings emerge from their seed in 5-10 days, and you must balance every environmental upshot to save them from turning yellow.

Generally, improper watering is the main reason behind Tomato seedlings turning yellow. However, other possible reasons like imbalanced sunlight, inappropriate fertilizer, diseases, and pests may also cause the yellowing of Tomato seedlings.

Besides turning yellow, they may show signs like drooping, curling, and wilting, with death in severe cases.

You can’t turn the yellow leaves to green, so you need to discard them to save energy for further growth of your seedling.

Tomato Seedlings Turning Yellow (Causes & Solutions)

Tomatoes thrive in warm weather and can grow in USDA zones 5,6,7, and 8 easily in the proper environment.

However, Tomato seedlings are fragile and can’t tolerate fluctuating environments. So, it’s better to harden them off before transplanting them in the garden.

Inspect the following causes to fix yellow leaves on Tomato seedlings.

1. Improper Watering

Overwatering causes root stress in Tomato plants due to no air circulation in waterlogged soil resulting in the Tomato leaves turning yellow and curling.

Tomato seedling  in dry soil (underwatered)
Not enough water for seedlings can cause yellow leaves

Moreover, underwatering causes the soil to dry out, and the seedlings may be deprived of nutrients turning their leaves yellow and crispy.

Sometimes, even if you water properly, your Tomato seedlings may turn yellow due to improper drainage or bad water condition.

Solutions and Preventive Measures

  • Remove the seedlings from the garden or pot carefully and transplant them into the moist soil.
  • Water the seedlings only when the soil becomes 1 inch dry, ensuring the soil is moist but not waterlogged.
  • Always use terracotta containers for potted seedlings and only distilled or rainwater for watering.
  • Use a moisture meter to balance the watering schedules.
  • The bottom watering method is best for extremely dry soil.
  • Avoid tap water containing chemicals such as chlorine and fluorine. 
  • Plant your seedlings in the well-draining, loamy, and fertile pH 5.8-7 soil, ensuring no high clay content and enough drainage.
You only need to keep the soil moist for the newly planted Tomato seedlings. Later, water them twice a week in the growing season.

2. Imbalanced Sunlight

Lack of sunlight causes the underside of the seedling’s leaves to turn yellow with no flowering.

However,  both seedling and adult Tomato plants may turn yellow or suffer from foliage burn due to excessive sunlight.

Solutions and Preventive Measures

  • Place your Tomato seedlings in the south-facing window if they are in potted condition.
  • Provide 14-16 hours of artificial light using grow light if natural light isn’t available.
  • Rotate the potted seedlings regularly for even light distribution to every part.
Note: Tomato seedlings need 8-12  hours of bright sunlight daily for healthy growth. 

3. Pests & Diseases

Sometimes, your Tomato seedlings may turn yellow due to diseases like root rot, molds, blights, etc.

These diseases are common in your Tomato seedlings and are caused by overwatering and pathogenic invasion.

Further, these diseases are spread to whole seedlings by insects and pests like stinks, beetles, spider mites, etc. 

Moreover, it’s easy for the pathogens to infect the area where the pests feed, leaving disgusting marks on the leaves.

Solutions and Preventive Measures

  • Use suitable pesticides and fungicides once a week but in very small amounts, as the seedlings are sensitive.
  • Neem oil is the safest option to eliminate fungal pathogens and pests.
  • Discard the seedling that is severely affected to prevent the spreading.
  • Throw away the old debris to prevent fungal infections.

Solution: Mix 4 tablespoons of baking soda with 1 gallon of water and a few drops of dish soap for homemade insecticidal spray.

4. Fertilizer Use

Tomatoes’ seedlings don’t need fertilizers as they are too young to handle the chemicals in the fertilizers.

Excessive fertilizers accumulate high salt content, making the soil dry and causing yellow leaves in the seedlings.

Scattered Tomato seedlings
Your seedling will hint to you about the imbalanced fertilizer by turning its lower leaves yellow.

Moreover, you will notice the white clumps on the drainage holes if you feed them too much.

However, if you aren’t feeding them additional fertilizer and they start turning yellow from the bottom, a small chunk of fertilizer will help.

Feed your Tomato seedlings with the fertilizer of NPK value 6-24-24 only when it bears its first set of true leaves.

Solutions and Preventive Measures

  • Hydrate the seedling before applying any fertilizer. Ensure to fertilize in very small amounts.
  • Carefully remove it from the soil and repot or transplant it into fresh soil after flushing the roots to remove excessive fertilizer.
  • Switch towards homemade compost for safe and healthy Tomato plants from the seedling stage.
  • Treat yellow leaves in Tomato plants with Epsom salt of 1-2 tablespoons for potted seedlings, and 1 cup per 100 sq feet of soil will prevent yellowing.

From Editorial Team


When the Tomato seed germinates, oval-shaped cotyledon leaves appear first to support the growth of seedlings.

After the growth of true leaves, these cotyledon leaves turn yellow and fall off naturally, hinting the healthy growth.

So you need not worry about yellowing the leaves that aren’t shaped like Tomato leaves.