yellowing tomato leaves: Why Are My Tomato Plant Leaves Turning Yellow?

Tomatoes, delicious addition to any salad or sandwich, are the most grown vegetable. Their bright red color makes any garden appealing and the smell of the plant reminds gardeners of summer.

While tomato plants are one of the easier vegetables to grow, issues can arise. One commonly report concern is yellow leaves on tomato plant.

Why are my tomato plant leaves turning yellow?

There are numerous reasons for why tomato leaves turn yellow, and usually it is nothing need to worry about. The most common reason that tomato plants turning yellow is because of watering stress. Overwatering or underwatering are the most common cause of Yellowing leaves on a tomato plant. Rather than watering lack of important nutrients like nitrogen, or diseases could be to blame here .

Keep reading to figure out what causes tomato plant leaves to turn yellow and what you can do to fix and prevent Yellowing of leaves on tomato plants from happening.

6 Common Causes for Yellowing Leaves on tomato plants

There are numerous reasons for yellow leaves on plants. Depending on what is causing the tomato plant stress there are numerous ways to fix it. Here is a quick look at the reasons for yellow leaves on your tomato plants.

Yellowing of the leaves can signal overwatering

Excess water

When plants get too much water you can drown them. This can cause a significant amount of stress and potentially turn some of the leaves yellow. It is important to know who much water plants need in order to work efficiently.

Deficient water

When plants don’t get enough water, they start prioritizing what they need to put their energy into. Similarly to the response to excess water, deficient water can also stress the plant out and cause leaves to turn yellow. Again, it is important to know how much water plants need.

Compacted soil

Soil needs to have a good amount of airflow. When it doesn’t have that the stress can cause the leaves to turn yellow.

Virus, fungi, or bacteria

Different diseases and fungi can attack plants and cause the leaves to turn yellow. The best way to deal with this is to watch for the signs of infection. Depending on the specific infector, there are different remedies.

Pests

Just like viruses, fungi, and bacteria, pests can attack plants and stress them out. Working to identify the pest is the best way to fix the problem. Depending on the pest there are various remedies to get rid of them.

Nutrient deficiencies

Imbalances of certain nutrients like nitrogen can make the plant start to show signs of stress. Other minerals and an imbalance of alkalinity are also possibilities.

There are certain fertilizers and home remedies that can be used to fix this imbalance. Compost can also help.

Lack of sun

Sun gives plants energy through the process of photosynthesis. If your tomato plants don’t get enough sun, they aren’t going to have as much energy which can turn their leaves yellow.

If your tomato plants are in pots, try moving them to a sunnier location. If you can’t move them, consider changing the garden location next season.

Normal stage of the growth cycle

Yellow leaves can also be something that you don’t need to worry about!

Reasons Why Are The Leaves On My Tomato Plants Turning Yellow

Let’s go into a bit more detail on the reasons for yellow leaves on tomato plants and the ways you can fix it.

Overwatering Causes yellow leaves on tomato plant

As mentioned above, overwatering as well as under watering can both cause tomato plants leaves to turn yellow.

First, starting with overwatering, tomato plants need to have the perfect levels of soil moisture. You should monitor your plants and determine how much your plant needs based on many factors.

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If you live in a cooler climate region, or if you get little rain, if your plants are in pots or the garden – all of these factors influence how often you water and how much water your plants need.

When you over-water your tomato plants, root-rot is a possible outcome. Even if you water your plants the perfect amount and your soil doesn’t drain well, root rot can still happen.

Root rot is a side effect of drowning and having too much water for an extended period of time. It causes the plant to struggle breathing. Without a flow of oxygen, the plant tissues start to die and will start to decay.

How To Fix/Stop yellowing tomato leaves From overwatering 

When leaves turn yellow at the base of the plant, it can indicate what is specifically called “fusarium root rot”. Another indication of root rot includes, the stem just above the soil turning brown.

If you notice either of these indicators, you can slightly dig around the stem (be careful not to damage the plant) to see if it is wet or wrinkled.

If your tomato plant is suffering from root rot and turning the leaves yellow, you need to catch it early. Unfortunately, if you didn’t catch it early, your tomato plant is likely going to die.

If you did not over water and if there was not a significant amount of rainfall, the plant likely has a fungus that has been dormant and was activated. If this is the case – the plant needs to be thrown away so not to infect others.

If you catch root rot early, you can try to save the tomato plant. Gently dig up the plant and rinse the roots with cold water to get rid of any soil. Decayed sections of the root may start to break off.

chop off some of the yellow tomato leaves

After washing, chop off any soft and mushy black sections of the root and wash a second time. You can either plant the tomato plant in different soil, or place the roots in a gentle fungicide to kill any fungus (if there is any).

Finally, chop off some of the yellow tomato leaves at the bottom of the plant so that more energy can be put into the regrowth of roots.

Underwatering Causes Yellow Leaves On Tomato Plant

On the other hand, under watering can also cause yellowing leaves on tomato plants. Fortunately, it is not as big of a deal as over watering.

The reason that the leaves of your tomato plants turn yellow, is because the plant doesn’t have enough energy to put into the entire plant, so some leaves start to decay.

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Now, if the soil has dried out, do not try to flood the plant. Slowly throughout the day, water the tomato plant and let it soak up the water. Cut the yellow leaves off from the base of the plant.

Compacted or non-aerated soil Can Cause Your tomato Plant To Get yellow leaves

Compacted Or Non-Aerated Soil Can Cause Your Tomato Plant To Get Yellow Leaves

You need to loosen the soil when you plant tomato plants. If you don’t, similarly to drowning the plant with water, the plant can’t breathe. This can cause tomato leaves to turn yellow.

The best way to handle this if you notice yellow leaves is to dig into the soil slightly and loosen it up.

While doing this, be careful not to damage the root system. Next, clip off the yellow leaves at the base of the plant.

Yellow Leaves on Tomato plants Sometimes Indicate Diseases And Pests

There are many predators that can harm your tomato plants. Many of them are fungi and some are bugs. Here are a few that can compromise the growing efficiency, and even kill your tomato plants.

1: Septoria Leaf Spot of Tomato

Septoria lycopersici is a fungus that attacks the foliage of the plant. It typically arises after times for extended wet periods.

It is not soil based so it has the ability to survive the winter by being on weeds. What’s more, some of your gardening equipment could be carrying some spores.

The leaves will have circular spots that are darker on the outer circle and a light brown center. They may even have yellow regions. The leaves may start to die when more spots appear on the leaf.

When dealing with the fungus, first, you need to clip off the diseased leaves. Add mulch to the surrounding of the plant to prevent soil splashes from hitting the leaves.

Water directly onto the soil instead of from above the plant. Finally, do not let the leaves of the tomato plants touch the soil. When the leaves touch the soil, it makes it easier for the fungus to spread.

2: tomato diseases caused by Fusarium oxysporum

Fusarium oxysporum is another fungus, but this one infects the plant through its root system. It decreases the ability of the plant to absorb water. This obviously can lead to wilting and potential death.

This disease starts with the tomato plant leaves turning yellow and will continue to wilt even if you are watering sufficiently. Leaves will even begin to fall off.

One of the best ways to prevent fusarium wilt, is to work to maintain the pH of the soil around 6.5. This helps limit the fungus from setting and taking over the plant. 

The good thing about this fungus is that it can only enter the plant through damaged roots, so it is important to prevent root rot and work to not damage the plant when digging through the soil.

Unfortunately, once your tomato plant is infected, it is unlikely that it will recover.

3: Alternariasolaniis

Alternariasolani is a fungus that appears on the lower and older leaves of the tomato plants. It can be detected because it has brown, “bullseye” spots. Eventually the leaves will turn yellow and wither. Treat this fungus similarly to the above mentioned, Septoria lycopersici.

4: Ralstoniasolanacearum

Ralstoniasolanacearum is a soil-born bacterium that is common in moist, humid and sandy soils. It moves up the roots and if your plant gets infected, remove and ideally burn it so that the bacteria doesn’t spread to the rest of your garden.

5: Verticillirnalboatrum

Verticillirnalboatrum is a fungus that is also soil-borne and lives in cool northeast gardens. The infection begins with yellow patches on the lower leaves and starts to produce brown spots.

Eventually, the leaves start to curl and they start to die. If your plant gets infected, chop off any branch that shows these signs. The plant can’t necessarily be saved, but you can treat the soil with fungicide to prevent more problems.

Finally let’s talk about bugs. They are not always obvious so if leaves start to turn yellow, you need to search under leaves and look closely at the stem.

Mealybugs and aphids are common. Spraying the leaves with a soapy water spray gets rid of some bugs.

Nutrient deficiencies Can Result In tomato plant's leaves Turning Brown

There are various deficiencies. Here are several of the most common deficiencies that can cause yellowing leaves on your tomato plant.

Compacted Or Non-Aerated Soil Can Cause Your Tomato Plant To Get Yellow Leaves
The reason that leaves can turn yellow when they don’t get enough nutrients is because the plant isn’t getting what it needs. It can’t put as much energy into keeping all the leaves green and it needs to prioritize where the energy is put. Nutrient deficiencies can typically be fixed by adding organic matter or chemicals to the soil to manually add the necessary nutrients.

Imbalanced alkalinity is a problem because tomato plants, specifically, need a certain pH range for efficient absorption of nutrients. If there is an imbalance, you can add a little bit of fertilizer to keep the pH maintained around 6.5.

Lack of nitrogen can turn the lower leaves yellow and the newer leaves will stay bright. However, general plant growth will drop and it will be stunted. Adding certain chemicals or organic matter that is higher in nitrogen to help to plant recover.

Potassium deficiency will turn the space in between the veins of the leaves yellow and they may even start to wilt.

Calcium deficiency will cause the newly growing tips yellow within a few days. This is commonly called “blossom end rot”.

Magnesium deficiency will cause stunted growth and the outer rims of leaves will become yellow – resembling a golden border. Yellow spots many start to appear on the leaves around the veins. When these two effects merge, the veins will remain green but the entire leaf will be yellow.

Sulfur deficiency is indicated by new leaves looking yellow and older leaves remaining green. This lack of nutrients can also lead to stunted growth.

Zinc deficiency is illustrated in the new leaves with the area between the veins turning yellow.

No cause for concern!

Finally, yellow leaves can be a typical reaction to the stage of growth that your tomato plants are in. It is a completely natural stage for older foliage to turn yellow and wilt.

Further, if you have just transplanted the plant, this can be an indicator of stress. Give it a few days to recover from the move before looking for other answers.

As long as the growth is not stunted and the fruits are still being produced, you don’t need to worry about other issues.

How can I prevent my tomato plant leaves from turning yellow?

The minute you bring a tomato plant home from the nursery or the minute you start your seeds, you should start a pest and disease prevention routine.

If buying pre-grown plants, look for ones that are dark green, with thick and stiff stems with no signs of lead spotting or yellowing. As you continue growing them, monitor their progress.

Another tip is to not buy tomato plants that are already flowering or bearing fruit because it will be harder for them to transition to a new home.

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When transplanting, keep in mind that they need at minimum 6 hours of direct sunlight. Further, be sure to plant them about 2 feet away from each other for smaller plants and about 4 feet for larger plants. 

This will be sure to give them enough space and increase the oxygen that can flow through the soil. Doing this also prevents the spread of diseases if one of your plants has the unfortunate situation of becoming infected.

When possible, you should water your plants at the base of the plant. Do not water from the top of the plant because this water coming into contact with the stem and leaves can increase the likelihood of disease or pests.

Finally, getting the proper type of tomato is also important. Some of them are tolerant to disease and fungal infections specifically. 

Can Epsom salts be used to fix yellow leaves on tomato plants? 

Many gardeners have preached about using Epsom salts to combat deficiencies. Epsom salts are made of both sulfur and magnesium.

Tomato plants use magnesium to help in the process of photosynthesis, the cell structure of the plant, and in fruit production.

Because Epsom salts contain 10% magnesium and 13% sulfur. They are typically, used as a magnesium supplement, but their effectiveness in amateur gardens is debatable.

For yellow leaves on tomato plants, using Epsom salts will not be an instant fix for the nutrient deficiency and your plants might even start to look worse before they get better. Many people also expect their fruits to get a lot bigger and juicer – this is not likely to be the case. It will only work if the soil is magnesium deficient.

To prepare a mix, combine 1 tablespoon Epsom salts with one gallon of water. Apply this mix to the soil in replacement of regular watering every few weeks.

If your plants are not magnesium deficient, this method can actually hurt your plants.

Frequently Asked Questions

Why are there brown, gray, and yellow spots on my tomato plant’s leaves? 

This can indicate a few different fungi infections, including Septoria. This soil-borne fungus affects the leaves and is common in areas with humid climates. It starts at the bottom of the plant and works its way up.

What if the whole tomato leaf turns yellow? 

This may not be a problem if the leaves are older and at the bottom of the plant. If the new leaves are turning yellow, you might have a nutrient deficiency. Fungi usually attack the plant from the bottom up or the whole plant at once.

Why are the leaves turning brown on my tomato plant? 

Brown leaves are the effect of a fungal attack. If you notice them going brown before turning yellow, you need to look for other signs of a fungal infection and determine a solution as soon as possible.

Why are the leaves dying? 

When leaves are older it is very normal for them to die, and fall off the plant – this is nothing to worry about. If you still see healthy leaves at the top, there is nothing to worry about.

Conclusion

When you go out to check on your tomato plants and you notice yellowing leaves, this can be concerning. The discoloration can be a result of certain deficiencies, pests, diseases etc. There are many reasons for yellow leaves. There is also the possibility that it can be a natural stage of development.

If there is any question and you can’t figure what is going on, clip off a branch and take it to a gardener friend, or a nursery and ask them for help. Limbs and leaves can grow back.

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