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5 Most Common Reasons For Tomato Seedling Leaves Turning Yellow

5 Most Common Reasons For Tomato Seedling Leaves Turning Yellow

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Tomato seedling leaves are turning yellow. So, you have finally decided to move forward with growing a tomato garden, but there’s one tiny problem: the tomato seedling has leaves starting to turn yellow.

Is that good or bad? What causes the leaves to be yellow? How do you fix it?

While there are several reasons for a tomato seedling’s leaves to turn yellow, it seems to be a common scenario that can be resolved.

This article lists the most common reasons and simple countermeasures I use when my tomato leaves turn yellow.

Tomato Seedling Leaves Turning Yellow

Tomato seedling leaves are turning yellow due to insufficient calcium and iron. Too little or too much watering, lack of sunlight, and diseases can also cause yellow leaves. However, yellow leaves are sometimes a normal part of development for tomato plants.

Tomato Seedling Leaves Turning Yellow
Tomato Seedling Leaves Turning Yellow

Most Common Reasons for Yellow Leaves on Tomato Seedlings

1. Nutrient Deficiencies Can Cause Leaves to Turn Yellow

Although tomatoes are one of the most popular crops to grow, they are very high maintenance. Tomato plants feed heavily on the nutrients in the soil, which can easily lead to deficiencies.

While lack of adequate nitrogen is the most likely culprit, especially if the entire leaf is turning yellow, newly sprouted leaves are more likely to be deprived of calcium and iron.

While you can usually resolve this issue by switching to high nitrogen fertilizer, you should test a soil sample to determine which nutrient the soil is lacking.

Of course, more nitrogen won’t make a difference if the plant needs more iron.

2. Too much or Too Little Watering Can Cause Yellow Leaves

Balance is a key factor when watering tomato plants, as overdoing or underdoing the watering will result in the plant showing signs of nutrient deficiencies, such as yellowing leaves.

While it may be tempting to go out in the garden with a watering can daily, this isn’t the best course of action when caring for tomato plants.

Tomato seedlings do fine with just an inch of water per week at the beginning of the season and two inches once they begin to produce fruit.

Tomato plants shouldn’t be watered more often than two times per week, but you should always strive for deep watering to allow your tomato plant to absorb as many nutrients as possible.

3. Lack of Sunlight Can Cause Yellow Leaves

If only the underside of the leaves turns yellow, or the yellowing only affects one side of the tomato plant, the cause may be a lack of sunlight.

Naturally, the side of the leaf that is facing the soil isn’t going to get as much sunlight as the top of the leaf. While there isn’t much you can do to resolve that situation, it isn’t anything that you need to worry about.

Now, if only one side of the entire tomato plant is turning yellow, you may need to begin rotating the pot so that both sides will have daily access to sunlight.

4. Diseases Can Cause Leaves to Turn Yellow

This doesn’t mean that your tomato plant is doomed, as diseases are common on tomato plants. Besides, there are other explanations for the yellowing leaves.

It doesn’t necessarily signify disease. However, the disease is one possible reason your tomato seedling turns yellow.

A few fungal diseases commonly occur on tomato plants, such as Septoria and Early Blight, both of which can cause yellowing leaves.

Some wilting conditions cause leaves to turn color and start to become wilted.

Fortunately, these diseases can be resolved with early detection, removing affected leaves, and treatment with a fungicide.

5. Yellow Leaves May Be Perfectly Normal

Yes, it is normal for the leaves of tomato seedlings to turn yellow when a tomato plant produces its very first leaves, which are referred to as seed leaves (or cotyledons).

These initial leaves will turn yellow and fall off the plant before being replaced with new leaves. This is normal for tomato plants.

Tomato plants are also known for developing yellow leaves at the end of the season following harvest, which is also perfectly normal.

Two other common reasons for leaves turning yellow are the soil being compacted too tightly and transplant shock after repotting tomato seedlings.

Frequently Asked Questions about Tomato Seedlings Turning Yellow

Should I Cut off the Yellow Leaves on the Tomatoes?

If the yellowed leaves are seed leaves, they will fall off on their own and not cause the plant harm, but yellowing leaves can be a sign of disease and nutrient deficiencies. Removing the yellow leaves can help prevent to spread of disease to the rest of the plant and prevent a deprived leaf from draining nutrients from the rest of the plant.

Why are leaves turning yellow on tomato plants?

The most common reason for yellowing leaves on tomatoes is overwatering. Reduce watering to avoid root rot.

What to do when tomato seedling leaves turn yellow?

It is important to act fast when you see discoloration in seedlings. Small plants are still weak. Every lost or sick leaf does not conduct as much photosynthesis as possible. Identify the main reason for the yellowing and initiate countermeasures.

Fixing Yellow Leaves on a Tomato Plant

If you notice yellow leaves on the lower half of your new tomato plant, it could be due to nitrogen deficiencies in the soil, in which case fertilizer or compost may resolve the issue.

So, back to the question: why are the tomato seedling leaves turning yellow? It’s hard to say.

It could result from nutrient deficiencies, improper watering, or diseases, or it may be completely normal.

If your tomato plant has yellow leaves, monitor the plant closely, alter the watering routine, loosen the soil, and rotate the plant.

Remove the discolored leaves and buy some fungicide if it doesn’t resolve independently.

Tomatoes are a delicious garden staple, but they are prone to disease and need just the right amount of water.

If you notice yellow leaves on your tomato seedlings, it is probably nothing to get worked up about, just your high-maintenance plant begging for some extra TLC.