Tomato Leaves Turning Yellow on Plant & How to Fix

There are several problems that result in tomato leaves turning yellow... Today I'm showing you what they are and how to fix the them! Keeping your tomato plants healthy is important for a bountiful harvest. I aim to uncover the reasons behind yellowing tomato plants and provide you with steps to help revive your plants.

When healthy tomato plants are at their best, You'll see vibrant green foliage, sturdy stems, and luscious tomatoes that are rich in color. But, it's essential to keep a close eye on the health of our plants to catch any problems early on. Yellowing leaves are a crucial indicator that something might be amiss.

Most Common Reasons Tomato Leaves Turn Yellow

Natural Aging

Tomato plants naturally shed older leaves as they age. These leaves typically start turning yellow and eventually dry up and fall off. It is a normal part of the plant's growth cycle, and removing them is not necessary unless they are severely diseased or damaged.

Tomato Seedlings and plants are prone to transplant shock and cause yellowing leaves if they aren't hardened off properly, if there's root damage, or if there is inadequate or overwatering.

Nutrient Deficiencies

One of the primary reasons for yellowing tomato plants is nutrient deficiencies. These precious plants require a balanced diet, just like we do! Nitrogen, magnesium, and iron deficiencies are common culprits behind yellowing leaves. I have learned to identify the symptoms associated with each deficiency and found effective remedies to restore my plants' vigor.

Yellowing leaves can be a sign of nutrient deficiencies, such as nitrogen, magnesium, or iron. In such cases, it's important to diagnose the specific nutrient deficiency and address it through appropriate fertilization or foliar sprays. If the yellowing is confined to older leaves and new growth appears healthy, there may be no need to remove the older leaves.

I've learned to keep a close eye on my tomato plants to ensure they receive the right nutrients for healthy growth. Recognizing nutrient deficiencies early on is crucial for maintaining robust plants. Here are some common nutrient deficiencies and how to identify them:

Nitrogen (N) Deficiency:
- Symptoms: A lack of nitrogen causes older leaves turn pale yellow, starting from the base of the plant and progressing upwards. The lower leaves may drop prematurely.
- Treatment: To address nitrogen deficiency, I apply a balanced organic fertilizer or incorporate compost into the soil. Nitrogen-rich amendments like blood meal or fish emulsion can also be used as foliar sprays.
Phosphorus (P) Deficiency:
- Symptoms: The leaves may appear dark green or bluish-green, and the plant's overall growth may be stunted. The plant may produce fewer flowers and fruit.
- Treatment: To tackle phosphorus deficiency, I add a phosphorus-rich organic fertilizer or bone meal to the soil before planting. Side-dressing with phosphorus-rich amendments during the growing season can also help.
Potassium (K) Deficiency:
- Symptoms: Older leaves develop yellow or brown spots, often starting at the leaf margins. Leaves may curl or develop a scorched appearance. The plant may show reduced vigor and lower resistance to pests and diseases.
- Treatment: To address potassium deficiency, I incorporate potassium-rich organic fertilizers, such as wood ash or kelp meal, into the soil. Regularly applying compost or composted manure can also help replenish potassium levels.
Magnesium (Mg) Deficiency:
- Symptoms: Interveinal chlorosis, where the areas between the leaf veins turn yellow while the veins remain green. The yellowing may progress towards the leaf margins, and leaves may curl or exhibit a brittle texture.
- Treatment: To combat magnesium deficiency, I apply Epsom salt (magnesium sulfate) as a foliar spray or add it to the soil. Incorporating compost or using composted manure can also help boost magnesium levels.
Iron (Fe) Deficiency:
- Symptoms: Younger leaves show interveinal chlorosis, with the veins remaining green while the areas between them turn yellow. In severe cases, leaves may develop white or brown spots and exhibit stunted growth.
- Treatment: To address iron deficiency, I apply chelated iron fertilizers as a foliar spray or incorporate iron-rich amendments, like iron sulfate, into the soil. Maintaining proper soil pH can also aid in iron uptake.

Treating Nutrient Deficiencies

Treating nutrient deficiencies involves a combination of soil amendments and foliar sprays. Steps to address nutrient deficiencies in my tomato plants:

Soil Testing: I start by conducting a soil test to identify the specific nutrient deficiencies present. This helps me tailor my treatments accordingly.
Organic Fertilizers: I choose organic fertilizers rich in the deficient nutrients, following the recommended application rates. I incorporate them into the soil or apply them as side-dressings around the plants.
Compost and Manure: Regularly adding compost or composted manure to the soil helps replenish essential nutrients and improve overall soil fertility.
Foliar Sprays: When dealing with severe nutrient deficiencies, I use foliar sprays containing specific nutrients. I follow the instructions provided by the product manufacturer for proper application.

Pest Infestations

Certain pests, such as aphids or spider mites, can cause yellowing of leaves as they feed on the plant's sap. In cases of severe infestation, removing heavily infested leaves can help control the pest population and promote plant health.

You can also treat the soil around the base of your tomato plants with DE or diatomaceous earth... A natural product that will kill pests. This will need to be reapplied regularly.

Watering

Over or under-watering can also lead to yellowing. By learning the art of proper watering, we can ensure our tomato plants receive just the right amount of moisture.

Water at the Base: When watering tomato plants, aim to water at the base of the plant, directly onto the soil. Avoid wetting the foliage as much as possible. Wet leaves create a humid environment that promotes the growth of fungal diseases and increases the risk of yellowing leaves.
Deep, Infrequent Watering: Water tomato plants deeply, providing enough water to reach the root zone. This encourages the development of deep, strong roots. However, avoid frequent shallow watering, as it promotes shallow root growth and makes the plants more susceptible to stress and diseases. Watering once or twice a week, depending on weather conditions, is generally sufficient.
Time of Day: Watering in the early morning is preferable. This allows the leaves to dry quickly, reducing the chances of prolonged leaf wetness and fungal diseases. Avoid watering in the late afternoon or evening, as the plants will remain damp overnight, increasing the risk of diseases.
Water Consistently: Maintain consistent soil moisture to prevent stress on the plants. Allow the top inch or two of soil to dry out slightly between waterings, but avoid letting the soil become completely dry. Check the soil moisture regularly by sticking your finger about an inch into the soil. If it feels dry, it's time to water.
Mulching: Apply a layer of organic mulch, such as straw, wood chips, or shredded leaves, around the base of the tomato plants. Mulch helps retain soil moisture, reduces weed growth, and regulates soil temperature. It also minimizes water evaporation, allowing the plants to make the most of each watering.
Avoid Overhead Sprinklers: If possible, avoid using overhead sprinklers or misters for watering tomato plants. These methods can wet the foliage excessively and promote disease development. Drip irrigation or soaker hoses are more suitable, as they deliver water directly to the soil without wetting the leaves.
Watering During Dry Spells: During prolonged dry periods, it may be necessary to supplement rainfall with additional watering. Pay attention to the moisture needs of the plants and adjust watering accordingly. Aim to keep the soil consistently moist, but not waterlogged.

Diagnosis & Troubleshooting

When our tomato plants turn yellow, it's crucial to become detectives and diagnose the underlying cause. By carefully observing and recording symptoms, examining our cultural practices, and seeking expert advice when needed, we can troubleshoot the issue.

As a home gardener, I have developed a step-by-step process (below) to narrow down the potential causes, ensuring I take the right actions to address the problem and restore the health of my tomato plants.

Environmental Stressors

Remember that our tomato plants can also affected by external factors that result in tomato leaves turning yellow. Temperature extremes, excessive sunlight, and insufficient or excess humidity can all stress our plants, resulting in yellowing leaves.

By creating a favorable growing environment and implementing protective measures, such as shading or providing adequate ventilation, we can shield our tomato plants from these stressors and keep them vibrant and green.

Overall Plant Health

Consider the overall health and vigor of the plant. If the yellowing leaves are limited to a few older leaves and the rest of the plant looks healthy, removal may not be necessary. However, if the majority of the plant is affected and shows signs of decline, removing some of the yellow leaves can help redirect energy to healthier parts of the plant.

Regular monitoring, proper nutrition, pest management, and disease prevention strategies can go a long way in maintaining the overall health of your tomato plants.

Prevention

Prevention is always better than cure, especially when it comes to our tomato plants. By implementing preventive measures, such as proper soil preparation and regular crop rotation, we can maintain the overall health of our plants and reduce the chances of yellow tomato leaves.

However, if we do encounter issues, there are specific treatments and remedies available. Nutrient supplementation, effective pest control methods, and disease management techniques can all be employed to nurse our yellowing tomato plants back to health.

Disease Management

Applying fungicides containing copper-based compounds or biofungicides containing Bacillus subtilis can also provide some protection against diseases that result in tomato leaves turning yellow.

Oh, the challenges we face as tomato gardeners! Fungal diseases can be a real headache when it comes to maintaining healthy tomato plants. These pesky infections cause yellow leaves, spots, and wilting... Leaving us worried and wondering what to do.

Fungal Diseases

Early Blight:
- Practice crop rotation by not planting tomatoes or related plants in the same spot for at least two years.
- Remove and dispose of infected plant debris to prevent the disease from spreading.
- Provide adequate spacing between tomato plants to improve air circulation.
- Water the plants at ground level to avoid wetting the foliage excessively.
- Apply organic fungicides containing copper or sulfur as directed on the product label to control the spread of the disease.
Late Blight:
- Monitor weather conditions and be especially cautious during periods of cool, wet weather.
- Avoid overhead watering and ensure that plants have proper drainage, too much water is a common problem.
- Remove and destroy any infected plant material immediately to prevent the spread of spores.
- Apply fungicides containing copper-based compounds or biofungicides containing Bacillus subtilis as a preventive measure.
- If the disease is widespread, consider removing and destroying severely infected plants to protect the healthy ones.
Powdery Mildew:
- Ensure proper air circulation by spacing plants appropriately and avoiding overcrowding.
- Choose tomato varieties that are resistant to powdery mildew if available.
- Provide adequate sunlight and avoid shading the plants unnecessarily.
- Water plants in the morning to allow foliage to dry before evening.
- Apply organic fungicides containing sulfur or neem oil at the first signs of infection or as a preventive measure.
General Preventive Measures for Fungal Diseases:
- Practice good sanitation by regularly disinfecting gardening tools with a solution of bleach or rubbing alcohol.
- Wash hands thoroughly after handling infected plants to prevent the spread of spores.
- Avoid working with plants when they are wet, as this can promote the spread of fungal diseases.
- Keep the garden free of weeds and remove any plant debris promptly.
- Mulch around tomato plants to prevent soil splashing and minimize fungal spore exposure.
- Monitor plants regularly for early signs of infection and take action promptly.

Fusarium Wilt or Verticillium Wilt

Identify and Confirm Fusarium Wilt:
- Observe the symptoms at the base of the plant, including wilting, yellowing, and browning of the lower leaves.
- Look for brown discoloration or dark streaks on the stem, especially at the base.
- Carefully dig around the affected plant to inspect the roots for signs of rot or discoloration.
- Confirm the presence of Fusarium wilt by consulting gardening resources or seeking guidance from local experts.
Prune and Remove Affected Portions:
- If the plant is severely infected, it's best to remove and destroy the entire plant to prevent the disease from spreading further.
- For mildly affected plants, carefully prune and remove the lower leaves and stems, ensuring not to spread the fungus to healthy parts.
- Disinfect pruning tools with a solution of bleach or rubbing alcohol between cuts to prevent the spread of the pathogen.
Soil Treatment:
- After removing the infected plant, carefully dig around the area and remove any remaining root fragments or infected soil.
- Dispose of the infected plant material and soil in a way that prevents further contamination.
- Consider solarizing the soil in that area by covering it with clear plastic to raise the temperature and kill remaining Fusarium wilt spores.
Soil Amendments and Biocontrol:
- Incorporate organic matter, such as compost or well-aged manure, into the soil before planting to improve its health and fertility.
- Consider using biocontrol agents, such as beneficial soil microbes or antagonistic fungi, that can help suppress the growth of Fusarium wilt.
- Follow the application instructions and guidelines provided by the biocontrol product manufacturer.
Adjust Planting Techniques:
- Practice proper spacing between tomato plants to promote good air circulation and reduce the chances of disease transmission.
- Avoid over-watering, as excessive moisture can create favorable conditions for the fungus to thrive.
- Consider planting Fusarium-resistant or grafted tomato varieties to minimize the risk of infection.

Septoria Leaf Spot

What to look for:

Leaf Lesions: Septoria leaf spot typically starts with small, circular lesions on the lower leaves of the plant. These lesions are dark brown or black with a lighter-colored center. They may have a yellow halo surrounding them.
Leaf Yellowing and Wilting: As the disease progresses, it makes tomato leaves turn yellow, wither, and eventually drop from the plant. The infection tends to move upward from the lower leaves to the upper foliage.
Stem and Fruit Damage: In severe cases, Septoria leaf spot can also affect the stems and fruit of tomato plants. Dark, sunken lesions may appear on the stems, and infected fruits may develop spots or blemishes.

Managing Septoria Leaf Spot

Strategies to effectively manage Septoria leaf spot and minimize its impact on your tomato plants:

Good Sanitation Practices:
- Remove and destroy any infected leaves, stems, or fallen debris from the garden area. This prevents the disease from spreading to healthy plants.
- Avoid composting infected plant material, as it may harbor the fungus. Instead, dispose of it in sealed bags or burn it.
Proper Plant Spacing and Air Circulation:
- Ensure adequate spacing between tomato plants to promote good air circulation. This helps reduce humidity levels and slows down the spread of the disease.
Mulching and Drip Irrigation:
- Apply a layer of organic mulch around the base of the plants to prevent soil splashing, which can spread the fungal spores.
- Use drip irrigation or water at the base of the plants to avoid wetting the foliage. Moisture on the leaves provides an ideal environment for the disease to thrive.
Fungicidal Treatments:
- Fungicides can be used to manage Septoria leaf spot, especially if the disease is severe or recurring. Consult with your local gardening expert or extension service to select an appropriate fungicide and follow the instructions for application.
Resistant Varieties and Crop Rotation:
- Consider planting tomato varieties that are resistant to Septoria leaf spot. These varieties have been bred to withstand the disease.
- Implement a crop rotation plan, avoiding planting tomatoes or other susceptible plants in the same area for several years. This helps reduce the buildup of the fungal spores in the soil.

Soil Compaction

Negative effects of soil compaction can contribute to tomato leaves turning yellow in several ways!

Restricted Root Growth: Soil compaction creates a dense and hard soil texture, making it difficult for tomato roots to penetrate and spread effectively. Restricted root growth limits the plant's ability to absorb essential nutrients and water from the soil. As a result, the plant may experience nutrient deficiencies, which can manifest as yellowing leaves.
Impaired Water Drainage: Compacted soil has poor water infiltration and drainage properties. Excess water can accumulate around the roots, leading to waterlogged conditions and oxygen deprivation. When roots lack oxygen, their functionality becomes compromised, resulting in poor nutrient uptake and nutrient imbalances that contribute to yellowing leaves.
Reduced Air Circulation: Compacted soil lacks sufficient pore spaces for air movement. Adequate oxygen availability is essential for healthy root function. Without enough oxygen, the roots may become stressed, leading to reduced nutrient uptake and impaired overall plant health. This stress can cause yellowing of leaves as a result of nutrient deficiencies.
Nutrient Imbalances: Compacted soil often hampers the natural decomposition of organic matter, which is crucial for nutrient cycling and soil fertility. The reduced organic matter content can disrupt the balance of essential nutrients in the soil, leading to nutrient imbalances in the plants. Nutrient deficiencies or excesses can manifest as yellowing leaves.
Limited Microbial Activity: Soil compaction can inhibit the activity of beneficial soil microorganisms that play a vital role in nutrient cycling and soil health. These microorganisms aid in breaking down organic matter, releasing nutrients for plant uptake. In their absence, the availability of nutrients to the tomato plants decreases, leading to yellowing leaves.

How to Fix Soil

To mitigate the effects of soil compaction and prevent yellowing leaves in tomato plants, you may want to do a few things.

Soil Amendment! Incorporate organic matter such as compost, well-rotted manure, or leaf mold into the soil. This improves soil structure, promotes root development, and enhances nutrient availability.
Mulching! Apply organic mulch, such as straw or wood chips, around the base of tomato plants. Mulch helps maintain soil moisture, reduces compaction caused by heavy rains, and encourages the activity of beneficial soil organisms.
Avoid Overwatering! Water tomato plants deeply but infrequently, allowing the soil to dry out slightly between waterings. Proper watering practices prevent waterlogging and help maintain good soil structure.
Soil Aeration! Loosen compacted soil by aerating it with a garden fork or mechanical aerator. This helps break up compacted layers and improves water infiltration and air circulation.

https://www.usda.gov/media/blog/2010/07/16/tomato-plant-diseases-and-how-stop-them

If you use this info to grow tomatoes and love it, Tag me on Instagram @farmhouse_harvest with your crop!