Why Are My Tomato Seedlings Turning Yellow?

Tomato seedlings turning yellow can be a sign of several problems, including nutrient deficiencies, pests, or diseases.

In this article, we’ll explore some of the most common causes of yellowing tomato seedlings and what you can do to fix the problem.

One of the most common causes of yellowing tomato seedlings is a nutrient deficiency. Tomatoes need a balanced supply of nutrients, including nitrogen, phosphorus, and potassium, to grow and produce healthy foliage.

If your seedlings are lacking in any of these nutrients, they may start to yellow. For example, a deficiency in nitrogen can cause the lower leaves of the seedlings to yellow, while a deficiency in phosphorus can cause the entire plant to yellow.

To fix a nutrient deficiency, you can try fertilizing your seedlings with a balanced tomato fertilizer or adding compost to the soil.

You can also try adding specific nutrients to the soil, such as nitrogen or phosphorus, if you suspect that your seedlings are deficient in a particular nutrient.

Pests can also cause tomato seedlings to yellow. Aphids, for example, are small insects that feed on the sap of plants and can cause the leaves of tomato seedlings to yellow and curl.

To control aphids, you can try spraying the seedlings with a garden hose to knock them off the plants or using an insecticidal soap.

Another possible cause of yellowing tomato seedlings is disease. One common disease that can affect tomatoes is called early blight, which is caused by a fungus.

Early blight causes the lower leaves of the seedlings to yellow and turn brown, and it can spread to the stems and fruit of the plant.

To prevent early blight, you can try rotating your tomato plants to a different location in the garden each year and removing any infected plants.

You can also try applying a fungicide to the seedlings to prevent the disease from spreading.

Here are a few more things to consider if your tomato seedlings are turning yellow:

  • Overwatering or underwatering: Both overwatering and underwatering can cause tomato seedlings to yellow. Overwatering can lead to root rot, which can cause the leaves to turn yellow and fall off. On the other hand, underwatering can cause the leaves to turn yellow and wilt. To fix these problems, make sure you are watering your tomato seedlings regularly and not letting the soil dry out completely.
  • Sunlight: Tomato seedlings need plenty of sunlight to grow, but too much direct sunlight can cause the leaves to yellow. If your seedlings are getting too much sun, try moving them to a shadier spot or providing them with some shade during the hottest parts of the day.
  • Transplant shock: If you recently transplanted your seedlings from a seed tray or small pots into a larger container or the ground, they may be experiencing transplant shock. This can cause the seedlings to yellow and wilt temporarily. To help your seedlings recover from transplant shock, make sure you are watering them regularly and provide them with some shade if necessary.
  • Herbicide damage: If you accidentally sprayed your tomato seedlings with an herbicide or if the seedlings were grown in soil that was treated with an herbicide, they may turn yellow as a result. To fix this problem, you will need to remove the seedlings from the contaminated soil and start over with new, untreated soil.

In summary, yellowing tomato seedlings can be caused by a variety of factors, including nutrient deficiencies, pests, and diseases.

To fix the problem, you can try fertilizing the seedlings, controlling pests, and preventing diseases. By taking these steps, you can help your tomato seedlings grow into healthy, productive plants.