If you're seeing yellow leaves on your tomato plants, don't panic! It's not the end of the world.

In fact, yellow leaves on tomato plants are a common problem, and there are many ways to fix it.

In this blog post, we will discuss the reasons why leaves turn yellow on tomato plants, and how to correct the problem.

So don't give up on your tomatoes just yet - read on for some helpful tips!

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Causes for Yellow Leaves on Tomato Plants

Leaves on tomato plants turning yellow are a common problem that has many causes.

In this article, we will discuss the most common reasons for leaves turning yellow on tomato plants and the solutions for each problem.

Now let's dig into the reasons why your tomato plant leaves might be yellowing.

Cotyledons (First leaves)

The first leaves that emerge from a tomato seedling are called cotyledons. These leaves are typically yellow or pale green in color.

If you see yellow leaves on your tomato seedling, and these are the first leaves to emerge, don't worry! This is normal and not indicative of a problem.

The cotyledons will eventually turn green as the plant grows and get its set of true leaves.

Nutrient Deficiency

Nutrient deficiencies are a common cause of yellow leaves on tomato plants.

Tomatoes are vigorous eaters and need a lot of nutrients to grow healthy and produce fruit.

So it is important that your soil meets the demands of your growing tomato plant.

The most common nutrient deficiencies that cause yellowing leaves are nitrogen, iron, and magnesium.

Nitrogen deficiency

One of the most common problems that gardeners face is yellow leaves on their tomato plants.

There are a number of reasons why leaves might turn yellow, but one of the most common is a nitrogen deficiency.

Nitrogen is an essential nutrient for plant growth, and it helps to produce chlorophyll, which gives leaves their green color.

Without enough nitrogen, tomato leaves will begin to turn yellow, starting at the bottom of the plant and working up.

In addition to leaves turning yellow, nitrogen deficiency can also cause stunted growth, poor fruit production, and even death of the plant.

Therefore, it is important to be aware of the signs of nitrogen deficiency and take steps to correct the problem as soon as possible.

The Solution

If you suspect that your tomato plants are suffering from a nitrogen deficiency, consider adding some organic matter to the soil to help improve its quality.

You may also need to fertilize more frequently to ensure that your plants are getting the nutrients they need.

Choosing a fertilizer with a balanced ratio is most likely your best option because if you use a nitrogen-rich fertilizer, you can end up with more leaf growth and less fruit development.

Make sure to always follow the manufacturer's instructions when fertilizing your tomato plants.

With proper care, you can avoid nitrogen deficiencies and keep your growing tomatoes healthy and productive.

Iron Deficiency

If yellow leaves on your tomato plants are accompanied by green veins, it is likely that the problem is an iron deficiency.

Iron is necessary for the production of chlorophyll, which gives leaves their green color.

An iron deficiency will cause the leaves to turn yellow, starting at the older leaves of the plant first.

The Solution

There are a few different ways to correct an iron deficiency.

One is to simply add more iron to the soil.

This can be done by using an iron-rich fertilizer or by amending the soil with iron sulfate or iron chelate.

Another option is to treat the tomato plants with a foliar spray of iron sulfate or iron chelate. Foliar sprays are generally more effective than adding amendments to the soil because they directly target the leaves, where chlorophyll is produced.

Whichever method you choose, be sure to follow the instructions carefully and avoid over-treating the plants, as too much iron can be just as harmful as too little.

Magnesium Deficiency

Magnesium is another nutrient that is necessary for the production of chlorophyll.

A magnesium deficiency will cause yellow leaves on your tomato plants, starting at with the older leaves.

You might see the leaves turn yellow around the edges and some brown or whitish spots. If it's a really bad deficiency, the leaves will turn yellow all over.

The Solution

Luckily, magnesium deficiency is relatively easy to correct. Gardeners can simply add some Epsom salt to the soil or spray the leaves with a solution of one teaspoon per gallon of water.

With a little care, yellow leaves will soon be a thing of the past.

Watering Issues

While yellow leaves can be a sign of a nutrient deficiency, they can also be caused by too much or too little water.

Over Watering

Tomato plants are notoriously fussy when it comes to watering, and too much water can lead to a host of problems, yellow leaves being one of them.

Overwatered tomato plants will often have yellow leaves that are wilted or yellow leaves with brown spots.

The yellow leaves are caused by a lack of oxygen in the soil, which prevents the roots from taking up nutrients. This can eventually lead to root rot.

In addition to yellow leaves, overwatered tomato plants may also experience blossom end rot and fruit cracking.

Not Enough Water

One of the surest signs that your tomato plants are not getting enough water is yellow leaves.

Yellow leaves can indicate a number of problems, but when they are accompanied by wilting, it is a sign that the plant is not getting enough water.

Other signs of water stress in tomato plants include leaf drop, smaller than normal leaves, and flowers falling off the plant before they can be pollinated.

If you see any of these signs, make sure to give your tomato plants a good watering.

The Solution

To avoid these problems, water your tomato plants deeply but only when the top inch of soil is dry.

Giving your plants a deep drink every few days is better than watering them lightly every day.

And be sure to mulch around your plants to help retain moisture and reduce evaporation.

Monitor your tomato plants for any signs of distress and make sure to adjust your watering accordingly.

Another great option for watering tomatoes is to use drip irrigation.

Drip irrigation applies water directly to the roots of the plant, so there is very little evaporation or runoff.

This method can be especially helpful in hot weather when tomato plants need a lot of water

Fungal Diseases

Fungal diseases are another common problem that can cause yellow leaves on tomato plants.

Some of the most common fungal diseases include early blight, bacterial wilt, septoria leaf spot, verticillium wilt, and fusarium wilt.

Early Blight

Early blight is a fungal disease that can affect the fruit, stem, and leaves of tomato plants.

The first signs of early blight are small, brownish-black spots on the lower leaves. The spots may get bigger and have concentric rings around them.

These spots will eventually turn yellow and spread, eventually causing the leaves to turn yellow and die. Early blight is most common in warm, wet weather.

The Solution

Taking care of your plants will help them stay healthy and resist early blight. Make sure to fertilize them well and keep them healthy overall.

Tomatoes can leave behind a lot of fungus in the soil. If you don't want to keep getting an infected plant, you should rotate your crops every 2-3 years.

Preventative application of fungicides is advised.

Bacterial Wilt

Bacterial wilt is another common fungal infection that can cause yellow leaves on tomato plants.

This disease is caused by a bacteria called Ralstonia solanacearum and it affects the vascular system of the plant, preventing water and nutrients from getting to the leaves.

The first signs of bacterial wilt are yellow leaves that wilt during the day but recover at night. The yellow leaves will eventually turn brown and die.

The Solution

Bacterial wilt is difficult to control because the bacteria can overwinter in the soil and infect new plants in the spring.

The best way to prevent bacterial wilt is to practice good crop rotation and remove the infected plant from the garden immediately. Then take measures to prevent the disease from spreading to other plants.

Septoria leaf spot

Septoria leaf spot is another fungal disease that can cause yellow leaves on tomato plants.

This disease is caused by the fungus Septoria lycopersici, which infects the leaves of the plant and causes tiny, circular, tan to gray spots to form on the lower leaves and stems of the plant.

The growth of these fungal spots is usually dark brown with a yellow halo around it.

The good news is that this fungal disease does not affect the fruit of the plant.

The Solution

To prevent septoria leaf spot, make sure to practice good crop rotation and remove any infected leaves from the garden immediately.

You can also apply a fungicide to your plants if you see any signs of the disease.

Try to prove good air circulation around your plants and avoid wetting the leaves when you water them.

Verticillium wilt

Verticillium wilt is another tomato disease that can cause yellow leaves on tomato plants.

This disease is caused by the fungus Verticillium albo-atrum, which infects the vascular system of the plant, causing the leaves to yellow and wilt.

The first signs of verticillium wilt are when you see yellow blotches on the bottom leaves. Then brown veins will start to show up. The last sign is when you see dark brown dead spots.

The Solution

The best way to control verticillium wilt is to prevent it from happening in the first place.

Start by planting disease-resistant varieties of tomatoes and make sure to rotate your crops every year.

If you do see signs of verticillium wilt, remove infected plants immediately and destroy them.

Transplant Shock

Transplant shock can also cause yellow leaves on tomato plants.

This usually happens when you transplant your seedlings too early or if the roots are damaged when you transplant them.

The first signs of transplant shock are yellow leaves, wilting, and stunted growth.

The Solution

To prevent transplant shock, make sure to wait until the weather is warm and all danger of frost has passed before you transplant your seedlings.

Be careful not to damage the roots when you transplant them and make sure to water them well.

For more specifics on transplanting your tomato seedlings, read this post about when to transplant your tomato seedlings so you can avoid transplant shock and get the best results.

RELATED: Tomato Leaves Turning White? What's Happening and How To Fix It.

Soil Compaction

Soil compaction is another reason that can cause yellow leaves on tomato plants.

This happens when the soil around the plant is too dense and prevents water and nutrients from getting to the roots.

It can be caused by heavy rain, over-watering, or even walking on the soil around the plant.

The Solution

There are several ways to prevent soil compaction. One is to avoid walking on wet soil. This will compact the soil and makes it more difficult for roots to grow.

Another way to prevent soil compaction is to use organic matter such as leaves and mulch. This helps to loosen the soil and improve drainage. Mulching also helps to prevent compaction by creating a barrier between the soil and the plant.

Finally, you can use a garden fork or rototiller to aerate the soil. Aerating the soil allows air and water to reach the roots more easily and improves air circulation.

By taking these simple steps, you can help to prevent soil compaction and maintain a healthy garden.

Not Enough Sunlight

Another common reason for yellowing tomato leaves is not enough sunlight.

Tomato plants need at least six hours of direct sunlight a day to grow properly.

If they don’t get enough sunlight, the leaves will start to turn yellow.

The Solution

If your tomato plants are not getting enough sunlight, you can try moving them to a sunnier location.

If that’s not possible, you can try using grow lights to give them the extra light they need.

End of Growing Season

Finally, yellow leaves on tomato plants can be a sign that the growing season is coming to an end.

As the days get shorter and the temperatures start to cool, the leaves will begin to turn yellow and fall off the plant.

The Solution

There’s not much you can do to prevent this since it’s a natural part of the plant’s life cycle.

However, you can prolong the growing season by using a tomato cage or trellis to support the entire plant. This will help the plant to keep producing fruit until the first frost.

How to Prevent Tomato Leaves Turning Yellow

There are a few things that you can do to prevent yellow leaves on tomato plants.

When you buy tomato plants, make sure to buy healthy plants that are disease resistant tomato varieties. This will help to prevent yellow tomato leaves caused by diseases and pests.
Another way to prevent yellow leaves is to start with healthy soil. Make sure to conduct a soil test first so you can add any amendments that may be needed.
Avoid overfertilizing your plants. This can cause the leaves to yellow and may even kill the plant.
Avoid using herbicides where you plan to grow tomatoes. Some herbicides can damage the leaves and cause them to yellow.
Pay attention to spacing when you plant your tomatoes. If the plants are too close together, they will compete for resources and the leaves may yellow.

By following these simple tips, you can keep your tomato plants healthy and prevent yellow leaves.

Why Tomato Plant Leaves Turn Yellow

If you have yellow leaves on your tomato plant, don’t despair. There are a few things that you can do to prevent yellow leaves on your tomato plant.

With a little care and attention, you can have a healthy tomato plant that produces delicious fruit all season long.

Yellow Leaves on Tomato Plants? Here's Why and How to Fix It.

How to fix yellow tomato leaves