Yellow Leaves on Tomato Plants? Here’s Why and How to Fix It!

Yellow leaves on tomato plants can be caused by a variety of factors, including lack of nutrients, disease, or pests. One common cause is a lack of nitrogen, which is essential for healthy leaf growth. Other possible causes include fungal or bacterial infections, insect infestations, or environmental stressors such as too much or too little water.

To fix yellow leaves on tomato plants, it is important to identify the underlying cause and take appropriate action. This may include adding fertilizer, treating for pests or diseases, or adjusting watering and light levels. Regular monitoring and proper care can help prevent yellow leaves on tomato plants and ensure a healthy and productive harvest.

Causes for Yellow Leaves on Tomato Plants

Yellow leaves on tomato plants can be caused by a variety of factors, including:

Nitrogen deficiency

Nitrogen deficiency is a common cause of yellow leaves on tomato plants. Nitrogen is an essential nutrient for healthy leaf growth and green color. A lack of nitrogen can cause the yellowing of the lower leaves on tomato plants, starting from the bottom and moving up the plant. The leaves may also appear smaller and have a lighter green color. The stem may also appear thin and weak.

To correct a nitrogen deficiency, you can add a fertilizer that is high in nitrogen to the soil around the base of the plant. You can also add organic matter, such as compost or aged animal manure, to the soil to provide a natural source of nitrogen. Additionally, you can also use a foliar spray that contains nitrogen, which will be absorbed by the leaves directly.

It’s important to note that too much nitrogen can also be harmful. It can promote excessive leaf growth at the expense of fruit production. Therefore, it’s important to follow the recommended guidelines on the fertilizer package and not to over-fertilize.

Iron Deficiency

Iron deficiency is another common cause of yellow leaves on tomato plants. Iron is an essential nutrient for the production of chlorophyll, which gives leaves their green color. A lack of iron can cause the yellowing of leaves, particularly between the veins. This is known as interveinal chlorosis. The affected leaves may appear pale green or yellow, while the veins remain green. This can also happen in other plants as well.

Iron deficiency is usually caused by soil pH levels that are too high. Tomatoes prefer a pH range of 6.0 to 6.8, and when the soil pH is higher than 7.0, it can cause iron to become less available to the plant. Additionally, high levels of phosphorous in the soil can also prevent iron uptake.

To correct iron deficiency, you can use a chelated iron fertilizer which will make iron available to the plant even at high pH levels. You can also lower soil pH by adding sulfur or sulfur-containing amendments. Avoiding high-phosphorus fertilizers and making sure the soil is well-drained will also help prevent iron deficiency.

Read: How Late Can You Plant Tomatoes? [5 Things To Know]

It’s important to note that iron deficiency can also be caused by other factors, such as pests or disease, so it’s important to correctly identify the underlying cause before taking action.

Magnesium Deficiency

Magnesium deficiency is another common cause of yellow leaves on tomato plants. Magnesium is an essential nutrient for photosynthesis and the production of chlorophyll, which gives leaves their green color. A lack of magnesium can cause the yellowing of leaves, particularly between the veins. This is known as interveinal chlorosis. The affected leaves may appear pale green or yellow, while the veins remain green.

Magnesium deficiency is usually caused by soil that is too acidic or too sandy and lacks organic matter. Magnesium can also be removed from the soil by excessive leaching or heavy harvesting.

To correct magnesium deficiency, you can add dolomitic lime to the soil to provide magnesium. Magnesium sulfate (Epsom salt) can also be used as a foliar spray, which will be absorbed directly by the leaves. Adding organic matter such as compost or aged animal manure to the soil can also provide a natural source of magnesium.

It’s important to note that magnesium deficiency can also be caused by other factors, such as pests or disease, so it’s important to correctly identify the underlying cause before taking action. It’s also important not to over-fertilize with magnesium as it can lead to other deficiencies.

Read Also: When to Plant Tomatoes in North Carolina

Watering Issues

Watering issues can also cause yellow leaves on tomato plants just like Oxheart tomatoes. Both underwatering and overwatering can stress the plant and cause the yellowing of leaves.

Underwatering can cause the leaves to wilt and turn yellow, as the plant is not getting enough water to support healthy growth. This can happen when the soil is too dry, the weather is too hot or windy, or the plant is not getting enough water. To fix this problem, you can increase the frequency of watering or make sure the soil stays evenly moist.

On the other hand, overwatering can also cause yellow leaves on tomato plants. When the soil is too wet, it can lead to a lack of oxygen which can cause the roots to suffocate. This can cause yellowing and wilting of leaves, as well as other symptoms such as spots or rot. To fix this problem, you can reduce the frequency of watering or improve drainage by amending the soil with organic matter.

It’s important to note that watering issues can also be caused by other factors, such as pests or disease, so it’s important to correctly identify the underlying cause before taking action.

Also Read: Do Tomato Plants Come Back in the Spring

Fungal Diseases

Fungal diseases can also cause yellow leaves on tomato plants. Some common fungal diseases that can affect tomato plants include:

  • Early Blight: This disease is caused by the fungus Alternaria solani and can cause yellowing and wilting of leaves, as well as dark spots on the leaves and stem.
  • Late Blight: This disease is caused by the fungus Phytophthora infestans and can cause yellowing and wilting of leaves, as well as dark spots and a white mold on the leaves and stem.
  • Septoria Leaf Spot: This disease is caused by the fungus Septoria lycopersici and can cause yellowing and wilting of leaves, as well as small brown spots on the leaves.
  • Fusarium Wilt: This disease is caused by the fungus Fusarium oxysporum and can cause yellowing and wilting of leaves, as well as wilting of the entire plant.

To prevent fungal diseases, it’s important to plant disease-resistant varieties and to practice good gardening hygiene, such as rotating crops and avoiding overhead watering. If a fungal disease is present, it’s important to treat the plants with a fungicide as soon as possible to prevent the spread of the disease.

It’s important to note that not all yellowing of leaves is caused by fungal disease, and it’s important to correctly identify the underlying cause before taking action. And to prevent tomatoes plants being too leggy read this guide.

Bacterial Wilt

Bacterial wilt is a disease that can cause yellow leaves on tomato plants. It is caused by the bacteria Ralstonia solanacearum, and it can affect a wide range of solanaceous plants, including tomatoes, peppers, eggplants, and potatoes.

Symptoms of bacterial wilt include yellowing and wilting of leaves, usually starting from the bottom of the plant and moving upward. As the disease progresses, the leaves will turn brown, and the entire plant can wilt and die. The wilting can occur suddenly, and often wilting is accompanied by a characteristic “ropiness” of the sap when a stem is cut. The bacteria can also be detected in the sap of infected plants by performing a bacterial streaming test.

Bacterial wilt is transmitted by the cucumber beetle, and it can also be spread by contaminated soil or equipment. To prevent bacterial wilt, it’s important to control cucumber beetles and to practice good gardening hygiene, such as rotating crops, avoiding overhead watering, and sanitizing equipment. Once a plant is infected, there is no cure, and the affected plant should be removed and destroyed.

It’s important to note that not all wilting and yellowing of leaves is caused by bacterial wilt, and it’s important to correctly identify the underlying cause before taking action.

Septoria leaf spot

Septoria leaf spot is a fungal disease that can cause yellow leaves on tomato plants. It is caused by the fungus Septoria lycopersici, and it can affect tomatoes, peppers, and eggplants.

Symptoms of Septoria leaf spots include small, round, brown, or black spots on the leaves, which can enlarge and merge together. The spots are usually surrounded by a yellow halo, and as the disease progresses, the leaves will turn yellow and wilt. The fungus can also cause stem cankers and fruit rot. This disease is more common in damp and humid conditions.

To prevent Septoria leaf spots, it’s important to plant disease-resistant varieties and to practice good gardening hygiene, such as rotating crops, avoiding overhead watering, and removing and destroying infected leaves. If the disease is present, it’s important to treat the plants with a fungicide as soon as possible to prevent the spread of the disease.

It’s important to note that not all yellowing of leaves is caused by Septoria leaf spots, and it’s important to correctly identify the underlying cause before taking action.

Verticillium wilt

Verticillium wilt is a fungal disease that can cause yellow leaves on tomato plants. It is caused by the fungus Verticillium dahliae, and it can affect a wide range of plants, including tomatoes, peppers, eggplants, potatoes, and many other plants.

Symptoms of Verticillium wilt include yellowing and wilting of leaves, usually starting from the bottom of the plant and moving upward. As the disease progresses, the leaves will turn brown, and the entire plant can wilt and die. The wilting can occur suddenly, and often wilting is accompanied by a characteristic “ropiness” of the sap when a stem is cut. The fungus can also cause stem cankers.

Verticillium wilt is transmitted by contaminated soil, and it can also be spread by infected plant debris. To prevent Verticillium wilt, it’s important to practice good gardening hygiene, such as rotating crops, avoiding overhead watering, and sanitizing equipment. Once a plant is infected, there is no cure, and the affected plant should be removed and destroyed.

It’s important to note that not all wilting and yellowing of leaves is caused by Verticillium wilt, and it’s important to correctly identify the underlying cause before taking action. Additionally, some tomato varieties are more resistant to the disease. Planting these varieties can help prevent the problem.

Transplant Shock

Transplant shock is a common problem that can cause yellow leaves on tomato plants. It occurs when a plant is moved from one location to another, and it is caused by the stress of being transplanted, which can disrupt the plant’s root system and cause a lack of nutrients.

Symptoms of transplant shock include yellowing and wilting of leaves, as well as slow growth. The plant may also appear stunted and weak. This can happen after a transplant or even after moving a container plant from indoors to outdoors or from one location to another.

To prevent transplant shock, it’s important to handle the plant gently during transplanting and to make sure the roots are not damaged. It’s also important to provide the plant with adequate water and nutrients and to protect it from environmental stressors such as extreme temperatures or strong winds.

It’s important to note that not all yellowing and wilting of leaves are caused by transplant shock, and it’s important to correctly identify the underlying cause before taking action. Additionally, providing the plant with proper care and attention to its needs will help it recover from transplant shock.

Soil Compaction

Soil compaction is a common problem that can cause yellow leaves on tomato plants. It occurs when the soil is compacted, which can make it difficult for roots to penetrate and absorb water and nutrients. This can cause stress on the plant, which can lead to the yellowing and wilting of leaves.

Symptoms of soil compaction include yellowing and wilting of leaves, as well as slow growth. The plant may also appear stunted and weak. Additionally, the soil may be hard and difficult to dig, and water may not be able to permeate through the soil easily.

To prevent soil compaction, it’s important to amend the soil with organic matter such as compost or aged animal manure. This will help to improve the soil structure and make it easier for roots to penetrate. It’s also important to avoid over-watering, as this can lead to waterlogging and compaction. Additionally, you can use a garden fork or aerator to break up compacted soil, and it’s important to make sure the soil has good drainage.

It’s important to note that not all yellowing and wilting of leaves are caused by soil compaction, and it’s important to correctly identify the underlying cause before taking action. Proper care and attention to the soil will help to prevent soil compaction and ensure the healthy growth of the plant.

Not Enough Sunlight

Not enough sunlight can cause yellow leaves on tomato plants, as tomatoes need adequate sunlight to produce energy through photosynthesis.

Symptoms of not enough sunlight include yellowing and pale leaves, as well as slow growth. The plant may also appear stunted and weak. The yellow leaves typically occur on the lower and inner parts of the plant, which receive less light than the upper and outer parts.

To fix this problem, you can move the plant to a sunnier location or provide additional artificial light. Tomatoes plants require at least 6 hours of direct sunlight per day to thrive. If the weather is too hot, you can also provide some shade to the plant during the hottest part of the day.

It’s important to note that too much sunlight can also be harmful to the plant, causing leaf scorching, wilting, and reduced fruit production. Therefore, it’s important to find the right balance of sunlight for the plant and to monitor the plant’s health to ensure it’s getting enough light.

End of Growing Season

As tomato plants near the end of their growing season, it is common for the lower leaves to turn yellow and die. This is a natural process known as senescence, and it is a sign that the plant is starting to shut down for the season. The yellow leaves will eventually turn brown and fall off the plant. This is normal and is not a cause for concern.

As the plant redirects its energy to ripening fruit and seed production, it will naturally shed its lower leaves that are no longer productive. This is a natural process, and it’s the plant’s way of conserving energy for the coming winter.

However, if the yellowing is excessive or starts from the top of the plant and progresses to the bottom, it could be caused by other factors such as disease or pests, nutrient deficiencies, or environmental stressors. In this case, it’s important to correctly identify the underlying cause before taking action.

It’s important to note that when the end of the growing season is approaching, you should stop fertilizing the plant and just focus on providing enough water. It’s also important to harvest the fruits that are ripe and ready to avoid over-ripe fruits falling on the ground and potentially causing a fungal infection.

Read: Cherokee Purple vs. Black Krim Tomato: A Growing Guide

How to Prevent Tomato Leaves from Turning Yellow

There are several steps you can take to prevent tomato leaves from turning yellow:

  1. Provide the right amount of sunlight: Tomatoes require at least 6 hours of direct sunlight per day to thrive. Make sure the plant is getting the right amount of sunlight and not too much or too little.
  2. Proper watering: Overwatering or underwatering can cause yellow leaves. Water the plants deeply and infrequently, and make sure the soil has good drainage.
  3. Proper nutrition: Provide the plant with the right amount of nutrients through fertilization. A balanced fertilizer can provide the necessary nutrients.
  4. Disease and pest control: Keep an eye out for signs of disease or pests and take action as soon as possible. Use organic or chemical control measures as appropriate.
  5. Proper pruning: Prune the plant regularly to remove dead or diseased leaves and to promote healthy growth.
  6. Soil management: Make sure the soil is well-draining and amended with organic matter such as compost or aged animal manure. This will help to improve the soil structure and make it easier for roots to penetrate.
  7. Avoid environmental stressors: Keep the plant protected from extreme temperatures, strong winds, and other environmental stressors.
  8. Use disease-resistant varieties: Some tomato varieties are more resistant to common diseases, such as early blight, late blight, and septoria leaf spots. These varieties will be less likely to develop yellow leaves due to disease.

Also Read Similar Guide: Fertilizer Burn on your Tomato Plants: Treatment & Prevention

Why Tomato Plant Leaves Turn Yellow

Tomato plant leaves can turn yellow for a variety of reasons, including:

  1. Nutrient deficiencies: A lack of essential nutrients such as nitrogen, phosphorus, potassium, or magnesium can cause the yellowing of the leaves.
  2. Watering issues: Overwatering or underwatering can cause stress on the plant, leading to the yellowing of the leaves.
  3. Fungal and bacterial diseases: Diseases such as early blight, late blight, and Septoria leaf spots can cause yellowing of the leaves.
  4. Pest infestations: Pests such as aphids and spider mites can cause yellowing of the leaves.
  5. Transplant shock: Moving a plant from one location to another can cause stress and disrupt the root system, leading to the yellowing of the leaves.
  6. Soil compaction: Compacted soil can make it difficult for roots to absorb water and nutrients, causing stress on the plant and yellowing of the leaves.
  7. Not enough sunlight: Lack of sunlight can cause photosynthesis to slow down, leading to the yellowing of the leaves.
  8. End of the growing season: As the plant nears the end of its growing season, it is natural for the lower leaves to turn yellow and die as the plant redirects its energy to ripening fruit and seed production.

By understanding the causes of yellowing leaves on tomato plants, you can take steps to prevent and correct the problem.

Also Read: Do Tomato Cages Work

Conclusion

In conclusion, yellow leaves on tomato plants can be caused by a variety of factors, including nutrient deficiencies, watering issues, fungal and bacterial diseases, pest infestations, transplant shock, soil compaction, not enough sunlight, and the end of the growing season.

It’s important to correctly identify the underlying cause before taking action, as the solution will vary depending on the problem. Some preventative measures include providing the right amount of sunlight, proper watering, proper nutrition, disease and pest control, proper pruning, soil management, avoiding environmental stressors, and using disease-resistant varieties.

By following these steps, you can help to prevent tomato leaves from turning yellow and promote healthy growth of the plant.