Yellow Leaves On Tomato Plants: Everything You Need To Know

Gardening is a process, and if you are new to planting and caring for plants, then it can sometimes be overwhelming. Gardening is a real skill, and it can take some time to really master this skill.

However, it is very common for you to get attached to your plants very early on in your gardening journey. That is why it can be heartbreaking if your plants appear to be unwell.

Just like all other living beings, plants will become unwell from time to time. However, with plants sickness can quickly become lethal. So, it is very important to spot if something is wrong with your plants very early on. 

In this guide, we’re focusing on tomato plants. One of the biggest health issues that tomato plants might experience is their leaves turning yellow.

In this guide, we’re telling you everything that you need to know about yellow leaves on tomato plants, including what could cause them and how to fix this issue. 

Read on to find out more. 

What Causes Yellow Leaves On Tomato Plants?

If you have previously attempted to grow your own tomato plants, then you will know that it is somewhat common for the leaves of your tomato plants to turn yellow.

Sometimes it is possible to save your tomato plants, other times, yellow leaves will be the beginning of the end. 

If you want to save your tomato plants as their leaves begin to turn yellow, then you will need to know some of the different things that could cause the leaves to turn yellow.

With that in mind, let’s take a look at some of the potential causes of this. 

Nutrient Deficiency

In order for your tomato plants to thrive, they will need a lot of nutrients.

Tomato plants get their nutrients from the soil in which they grow, so if your soil isn’t providing enough nutrients to the tomato plants, then there is a risk that the leaves will turn yellow.

The most common nutrient deficiencies that you will find in soil are nitrogen, iron, and magnesium deficiencies.

So if you notice something isn’t right with your tomato plants, you should test the level of these nutrients in the soil. 

Nitrogen Deficiency 

Nitrogen deficiency is one of the most common causes of yellow leaves on tomato plants. Nitrogen is an essential nutrient for plant growth, and without it, your tomato plants will struggle to grow.

As they struggle to grow, the leaves of the plants might turn yellow due to the lack of chlorophyll in the plants.

The Solution

If you suspect nitrogen deficiency, you should consider supplementing the soil with organic matter.

Organic matter will break down in the soil and improve the quality of the soil by increasing nitrogen. You should also consider fertilizing the soil.

Iron Deficiency 

Iron deficiency is something else that could impact the growth of your tomato plants. If the yellow leaves on your tomato plants are accompanied by green veins, then it is likely that iron deficiency is the cause of your issues.

Iron deficiency will cause leaves that were once green to turn yellow, starting with the oldest leaves. 

The Solution

The easiest way to resolve this issue is to add more iron to the soil. An iron sulfate or iron chelate is perfect for adding to your soil if you want to increase the iron and resolve the issue with your tomato plants. 

Magnesium Deficiency

When the leaves on your tomato plant turn yellow, it is often caused by a lack of chlorophyll.

Chlorophyll is responsible for the green color of the leaves on your plants, and magnesium plays a huge role in producing chlorophyll. So, if the leaves on your tomato plant are turning yellow, then this could be caused by a magnesium deficiency. 

The Solution

If you suspect that magnesium deficiency is the cause of your tomato plant issues, then you should use Epsom salts to resolve the problems.

You can either add the salts to the soil or spray the leaves with an Epsom salt-water solution. This will increase the magnesium that gets to your tomato plants. 

First Leaves

If you are growing your tomato plants from a seed, then there is no need to stress when you first see yellow leaves. Tomato seedlings have leaves that are called cotyledons, and cotyledons are always yellow in color.

This essentially means that the first leaves on your tomato plant seedling will always be yellow. 

In this situation, there really is no solution to the problem because there isn’t a problem. Your tomato plant leaves are supposed to be yellow at this stage in their life, so there is no need to worry!

The Impact Of Water On Tomato Plants

However, the cause of yellowing leaves on a tomato plant isn’t always caused by deficiencies. One of the essentials for growing plants is water, but it is very easy to either overwater or underwater your tomato plants.

To understand the importance of watering your plants, let’s take a look at how water can cause yellowing leaves in tomato plants. 

Not Enough Water

Like some plants, tomatoes are notoriously fussy when it comes to watering them.

When you are planting tomatoes for the first time, it is very easy to mess up the amount of water you give them, and this can cause the leaves to turn yellow. 

If your tomato plants aren’t getting enough water, then it is common for the leaves to start to wilt and turn a yellow color.

If you notice the leaves starting to wilt, you should increase the amount of water that you give your tomato plants. This will generally fix the issue with the color of the leaves too. 

Too Much Water

Likewise, if you give your tomato plants too much water, then this can cause the leaves of the tomato plant to change color. 

The tricky thing with this is that the leaves will wilt and turn yellow regardless of whether the plants are overwatered or underwatered.

So bear in mind the amount of water you give your plants to figure out what is causing the issue with the leaves. 

The Effect Of Fungal Diseases

It is also possible that the cause of your yellow leaves could be a fungal disease. There are lots of different fungal diseases that can impact tomato plants, including the following. 

Bacterial Wilt

One of the biggest fungal diseases that your tomato plants might encounter is bacterial wilt. This disease targets the vascular system of the plant and prevents nutrients from reaching the plant.

So, the tomato plants will be unable to direct water and nutrients to the leaves, meaning that they turn yellow in color.

The Solution

Bacterial wilt is very difficult to control because the disease develops in the soil during the winter months.

To try to control this, you should have a good rotation of plants and remove any infected plants immediately before the disease spreads.

Early Blight

Early blight is a fungal disease that targets pretty much the entire plant.

The first signs of this disease are small brown spots on the lower leaves of the plant, as the disease progresses, the spots will generally grow into rings, and the leaves will eventually turn yellow.

With this disease, by the time the leaves turn yellow, the plants are generally past saving.

The Solution

Once the disease has progressed, you will not be able to save your plants. But fertilizing the soil early on in the life of your tomato plants is a brilliant way to prevent the disease from impacting your plants. 

Septoria Leaf Spot

Another disease that causes yellow leaves and spots to develop on your tomato plants is Septoria Leaf Spot. This disease isn’t deadly as it does not affect the fruit of the plant, instead, it only affects the plant itself. 

The Solution

The best way to prevent Septoria Leaf Spot from affecting your tomato plants is to practice good and regular plant rotation.

Remove any affected leaves from the plants and ensure that you take good care of your plants to prevent the disease from spreading. 

Verticillium Wilt

Finally, Verticillium Wilt could be the cause of the yellow leaves on your tomato plant. This disease is a tomato-specific disease that targets the vascular system of the plant. It impacts the tomato plant in a similar way to bacterial wilt.

So the leaves of the plant will turn yellow as they are not accessing any of the water or nutrients that the roots are taking in from the soil.

The Solution

The solution to Verticillium wilt is to prevent it from happening in the first place. The best way to do this is to plant disease-resistant varieties of tomatoes and rotate your crops every year after harvest. 

The Planting Process

It is also possible that the yellow leaves on your tomato plant could be caused by the planting process. There are lots of elements of the planting process that could damage your tomato plants.

So, let’s take a look at what they are. 

Soil Compaction

If the soil that you plant your tomato plants into is too compact, this can cause the leaves of your tomato plants to turn yellow.

Compact soil will be too dense for the roots of your tomato plant to penetrate, so the number of nutrients that your tomato plant will be able to access will be severely limited.

In the long run, not only will the leaves turn yellow, but the plant will also fail to grow to its full potential.

The Solution

When planting the tomato seeds, ensure that the soil is loose. Then as the seeds start to grow, avoid walking on any wet soil in the area where you have planted your tomatoes.

Both of these things will help prevent the soil from becoming compact. 

Transplant Shock

Transplant shock is something that most gardeners will observe at some point in their lives.

With tomato plants, this is particularly common when the plants are transferred when it is still a little too cold for the tomato plants to thrive.

It will affect different plants in different ways, with tomato plants it is common for the leaves to turn yellow. 

The Solution

To avoid transplant shock, you should take care when transferring your tomato plants. Ensure that all the frost has passed before you do this and that you do not damage the roots during the transfer process. 

Planted Too Late

If you plant your tomato plants too late in the season, then they can be impacted by yellow leaves.

Tomatoes are seasonal plants and they are also very fussy, this means that you have to plant them within a specific time window for the plants to thrive. 

The Solution

Ensure that you plant your tomato plants early on in the season to give them plenty of time to grow. 

Not Enough Sunlight

Finally, if your tomato plants aren’t getting enough sunlight, you might observe that the leaves start to turn yellow.

Chlorophyll is responsible for making the leaves green, and the sunlight is essential for the production of chlorophyll. So, if your leaves are turning yellow, it is likely because your tomatoes aren’t getting enough sunlight.

The Solution

When planting your tomato plants, you should plant them in a position that gives them ample sunlight. If possible, you should move your tomato plants if you suspect they aren’t getting enough sunshine. 

How To Prevent Your Tomato Leaves From Turning Yellow

In this guide, we have taken a look at a lot of solutions for what to do if you notice that your tomato leaves are turning yellow. However, you might also be looking for ways to prevent this from happening. 

If you want to prevent your tomato leaves from turning yellow, follow the tips below.

These tips will really reduce the risk of your tomato leaves turning yellow, and increase the chances of your tomatoes growing and remaining healthy. 

Some top tips include:

• Ensure you do not over-fertilize your plants – always follow the instructions on the fertilizer. 
• Plant your tomatoes into fresh and healthy soil – complete a soil test before planting to ensure that the soil is healthy. 
• If you are planting tomato plants that are already partly grown, you should ensure that the plants are completely healthy before you plant them. 
• Don’t use any herbicides in the area of your garden where you plan on planting tomatoes as this could affect their growth. 
• Avoid planting your tomato plants too close together, leave large gaps to ensure each plant has plenty of space to grow and thrive. If resources are limited, your tomato plants will be more at risk. 

As well as following the tips above to prevent your tomato plants from going yellow, we would recommend making yourself aware of the different things that can cause your plants to become yellow.

That way, you can act quickly if your plants do begin to discolor.

So Why Do Tomato Leaves Turn Yellow?

As you can see in this guide, there are lots of reasons why your tomato plants might begin to turn yellow. When this happens, the most important thing to do is not panic.

While some causes can be lethal for your tomato plants, there are a lot of potential causes that you will be able to fix. But if you panic, you might not be able to save your tomato plants in time. 

With lots of different potential causes for the leaves on your plant turning yellow, it is important to identify the cause quickly and act on it. Otherwise, you could cause irreparable damage to your tomato plants. 

However, we can’t say for certain exactly what is the cause of your leaves turning yellow. This is something you will have to figure out for yourself.

But hopefully, the information included in this guide will aid you in figuring out what is causing the issues with your tomato plants. 

Summary 

In short, there are lots of different reasons why your tomato plants might begin to turn yellow. If the leaves of your tomato plants are turning yellow, then it is a surefire sign that something isn’t right with your tomato plants.

So, if you notice that your tomato plants are turning yellow, you really need to act quickly if you want to save them. 

In this guide, we have taken a look at pretty much all the different possible reasons why your tomato plants might be turning yellow. We’ve also included lots of tips on how to save them before they die. 

We hope that this information has been helpful. Thanks for reading! 

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