Why Are My Tomato Leaves Turning Black?

Tomato leaves turn black due to several possible causes, such as fungal infections or environmental stressors. If you have noticed that the leaves of your tomato plants are turning black, it can be an alarming sight.

The discoloration can range from dark brown to black, affecting the entire leaf or only certain parts. This issue can be caused by various factors, including fungal infections like early or late blight, which thrive in moist conditions.

Environmental stressors, such as over-watering, excessive heat, or inadequate sunlight, can also lead to the blackening of tomato leaves. Identifying the exact cause is crucial to implementing appropriate measures to stop the blackening and ensure the health of your tomato plants. We will explore the possible reasons for tomato leaves turning black and provide valuable tips to address the problem effectively.

Nutritional Deficiencies

Tomato plants are typically robust and resilient, but when their leaves start turning black, they can cause concern. One of the reasons behind this issue is nutritional deficiencies. If a tomato plant lacks essential nutrients, it can exhibit various signs, including blackened leaves. By understanding the specific deficiencies and associated symptoms, you can take the necessary steps to rectify the problem and restore your tomato plants to their healthy, vibrant glory.

Nitrogen Deficiency

A lack of nitrogen can result in blackening tomato leaves. Nitrogen is a vital nutrient required for crop growth as it aids in chlorophyll production, which gives leaves their green color. When tomato plants lack nitrogen, their leaves may develop a dark purple or black hue, indicating a deficiency. Additionally, you may notice stunted growth and a general decline in overall plant health.

Calcium Deficiency

Another common cause of tomato leaf blackening is calcium deficiency. Calcium is crucial for the structural integrity of cell walls and membranes, allowing plants to withstand environmental stressors. When calcium is scarce, tomatoes may develop a condition known as “blossom end rot,” where the bottoms of the fruits become black and leathery. Their leaves may also turn black due to the lack of calcium.

Boron Deficiency

Boron deficiency can also contribute to blackened leaves in tomato plants. Boron aids in transporting sugar and forming new cells, making it an essential micronutrient for plants. If tomato plants lack boron, their leaves may exhibit bluish-gray spots, followed by a blackened appearance. Further symptoms of boron deficiency include distorted growth patterns and reduced flower production.

To address these nutritional deficiencies, it’s essential to provide the affected tomato plants with the missing nutrients. Organic options such as compost, well-aged manure, and fish emulsion can enrich the soil. Commercial fertilizers specially formulated for tomatoes can also be applied according to the package instructions. Regular watering and appropriate soil pH levels also contribute to nutrient absorption.

By identifying and addressing the specific nutritional deficiencies causing the blackening of tomato leaves, you can nurture your plants back to health. Ensuring proper nutrition will resolve the black leaf issue and promote overall plant vigor, leading to an abundant harvest of delicious, vibrant tomatoes!

Fungal Diseases

Tomato leaves turning black can signify fungal diseases, such as early or late blight. These diseases are caused by fungal pathogens that thrive in moist conditions, resulting in black spots and wilting of the leaves. To prevent fungal diseases, ensure proper ventilation, avoid overhead watering, and remove affected leaves promptly.

Early Blight

Regarding tomato plants, early blight is one of the most common fungal diseases that may cause black leaves. Early blight, caused by the fungus Alternaria solani, usually starts by affecting the plant’s lower leaves. This disease thrives in warm and humid conditions, making it more prevalent during the hot summer. Infected tomato leaves develop small, dark spots with concentric rings, which eventually turn black. If left untreated, the disease can spread to other plant parts, including the stems and fruits.

Late Blight

Late blight is another fungal disease that can result in tomato leaves turning black, caused by the fungus Phytophthora infestans. Late blight is notoriously known for pushing the Irish potato famine in the 1840s and continues to be a significant threat to tomato plants. This disease thrives in cool and wet conditions, making it more common during heavy rainfall or high humidity periods. Infected tomato leaves develop irregularly shaped, dark green to black lesions with a fuzzy appearance. As the disease progresses, these lesions become water-soaked and emit a foul odor. Both early and late blight can harm tomato plants, causing leaf discoloration and defoliation and ultimately reducing the yield and fruit quality. It is essential to be vigilant and take necessary preventive measures to control these fungal diseases. To prevent early blight and late blight, consider the following tips:

  1. Avoid overhead watering, as it can increase humidity levels and create an ideal environment for fungal growth.
  2. Water the plants at the base or drip irrigation to dry the leaves.
  3. Ensure adequate spacing between plants to promote air circulation and reduce humidity.
  4. Regularly remove any affected leaves or plant debris from the garden to prevent the spread of disease.
  5. Apply a protective fungicide to the plants, following the manufacturer’s instructions.

These preventive measures can significantly reduce the risk of early and late blight affecting your tomato plants and ensure healthy and vibrant foliage. Remember that early detection and prompt action are crucial to managing these fungal diseases effectively. Look for any blackening leaves and take appropriate measures to protect your tomato plants.

Bacterial Infections

Bacterial infections are a common cause of tomato leaves turning black, and they can seriously impact the health and yield of your plants. Bacterial Speck and Bacterial Spot are two prevalent bacterial infections that can affect tomato plants. Understanding these infections and their symptoms is crucial for effective disease management.

Bacterial Speck

Bacterial Speck is caused by the bacterium Pseudomonas syringae pv. Tomato. It typically appears as small, dark brown to black spots on the leaves, about the size of a pinhead. These spots are usually surrounded by a yellow halo, making them easily distinguishable from other diseases.

As the infection progresses, the spots may merge, forming larger irregular-shaped lesions. The affected leaves may begin to curl or twist, and in severe cases, they may die and drop prematurely. The bacteria can spread through wind, water, or contaminated gardening tools, so it’s essential to take preventative measures.

Bacterial Spot

Bacterial Spot is caused by the bacterium Xanthomonas campestris pv. vesicatoria. It can affect various plant parts, including leaves, stems, and fruit. Symptoms of Bacterial spots on tomato leaves primarily appear as dark, greasy-looking spots with irregular margins.

These spots may start as small, water-soaked lesions, which gradually expand and turn black over time. Infected leaves may turn yellow around the lesions, and the tissue may eventually dry out and become brittle. Fruit infected with Bacterial Spots may develop dark, raised lesions that render them unsuitable for consumption.

Bacterial Spot is favored by warm and wet conditions, often due to overhead irrigation or high humidity. Proper cultural practices, such as avoiding overhead watering and providing sufficient spacing between plants to enhance air circulation, can help reduce the incidence and severity of this infection.

It is worth noting that both bacterial specimens and bacterial spots can be managed through a combination of cultural practices and the use of disease-resistant tomato varieties. Suppose you suspect your plants are infected with a bacterial infection. In that case, it is recommended to remove and destroy any affected plant parts, disinfect gardening tools, and employ practices that promote plant vigor and resistance.

Environmental Factors

When it comes to the health of your tomato plants, a variety of environmental factors can come into play. Understanding these factors is critical to diagnosing and treating the issue when your tomato leaves turn black. This post will focus on two major environmental factors contributing to blackening tomato leaves: excessive sunlight and overwatering.

Excessive Sunlight

Tomato plants need plenty of sunlight to thrive, but too much of a good thing can be harmful. Excessive sunlight can cause the leaves to become scorched and eventually turn black. When tomatoes are exposed to intense sunlight for long periods, it can lead to a condition known as sunscald. This occurs when the high temperatures and harsh sun rays damage the leaves, causing them to wilt, turn brown, and eventually blacken.

To protect your tomato plants from excessive sunlight, consider providing shade during the hottest parts of the day. This can be achieved by using shading fabric or strategically placing your plants near taller plants that can provide natural shade. A mulch layer around the plant’s base can also help regulate soil temperature and prevent excessive heat stress.


While tomato plants need regular watering, overwatering can lead to many problems, including blackened leaves. When tomato plants receive too much water, the roots become waterlogged, causing the leaves to become dark and blackened. Overwatering not only suffocates the origins but also prevents them from absorbing vital nutrients from the soil.

To avoid overwatering, it is essential to water your tomato plants consistently but not excessively. The frequency and amount of water needed will depend on factors such as weather conditions, soil type, and the stage of growth of the plants. To prevent waterlogging, ensure the soil has good drainage by incorporating organic matter such as compost or vermiculite. Additionally, using a well-draining pot or planting in raised beds can help prevent water from pooling around the roots.


To summarize, environmental factors such as excessive sunlight and overwatering can cause tomato leaves to turn black. You can help your tomato plants stay healthy and thrive by providing appropriate shade and avoiding overwatering. Monitoring the environmental conditions and making necessary adjustments will go a long way in preventing blackened tomato leaves and ensuring a bountiful harvest.

Prevention And Treatment

Tomato leaves turning black can signify issues such as fungal diseases, nutrient deficiencies, or environmental stress. Prevention and treatment involve:

  • Proper plant care.
  • Regular inspection for pests or diseases.
  • Providing adequate sunlight, water, and nutrients.

Consider using organic fungicides and adjusting soil pH levels to maintain healthy tomato plants.

Maintaining Proper Nutrition

Your tomato plants require a balanced diet to stay healthy and disease-free. Maintaining proper nutrition can help prevent your tomato leaves from turning black. Ensure that your plants receive adequate nutrients, such as nitrogen, phosphorus, and potassium, through regular fertilization. You can use organic or synthetic fertilizers based on your preference. Be sure to follow the instructions on the fertilizer packaging to prevent over or under-fertilization.

Additionally, consider the soil pH levels. Tomato plants thrive in slightly acidic soil conditions with a pH ranging from 6.0 to 6.8. Test the pH of your soil using a soil testing kit and make necessary adjustments by adding lime to raise the pH or sulfur to lower it. Maintaining the appropriate pH level will promote nutrient absorption and support the overall health of your tomato plants.

Using Fungicides

Fungicides can be an effective tool in preventing and addressing the issue of blackening tomato leaves caused by fungal infections. When applying fungicides, it is essential to follow the instructions provided by the manufacturer to ensure proper usage and dosage. Here are a few key points to consider:

  1. Select a suitable fungicide based on the fungal disease affecting your tomato plants. Fungicides containing copper, chlorothalonil, or mancozeb are commonly recommended for tomato fungal diseases.
  2. Apply the fungicide early in the season as a preventive measure or at the first signs of disease. Following the recommended frequency, regularly spraying your plants with the fungicide can help protect them from potential infections.
  3. Cover both sides of the leaves, stems, and fruits with the fungicide spray for maximum effectiveness. Ensure good coverage by using a fine mist sprayer and adjusting the nozzle.

Practicing Good Hygiene

Practicing good hygiene is crucial for preventing the spread of diseases in your tomato plants. Here are a few simple yet effective measures you can take:

  • Remove affected plant parts: If you notice any blackened or diseased tomato leaves, stems, or fruits, promptly remove them from the plant. This will prevent the spread of disease to other healthy parts.
  • Keep the garden clean: Regularly clean fallen leaves, weeds, and other garden debris. This helps eliminate potential hiding places and breeding grounds for pests and diseases.
  • Sanitize gardening tools: After each use, clean your gardening tools, especially if you have been working with infected plants. Sanitizing tools with a mixture of water and bleach or rubbing alcohol can prevent the transfer of diseases.
  • Avoid water splashing: Avoid overhead watering or excessive splashing on the foliage when irrigating your tomato plants. Wet leaves are more susceptible to fungal infections. Instead, use soaker hoses or target the water directly to the base of the plants.


Blackened tomato leaves can indicate potential problems, including fungal diseases, nutrient deficiencies, and environmental stress. By closely inspecting the affected leaves and considering other factors, such as watering practices and pest presence, gardeners can determine the cause and take appropriate steps to resolve the issue.

Adequate plant care, regular monitoring, and prompt action can prevent further leaf damage and ensure healthy tomato plants.

Frequently Asked Questions On Why Are My Tomato Leaves Turning Black

How Do You Treat Black Leaves On Tomato Plants?

To treat black leaves on tomato plants, remove affected leaves immediately, provide adequate sunlight and air circulation, water plants at the base to prevent wet foliage, avoid overcrowding, and use fungicides if necessary.

What Does An Overwatered Tomato Look Like?

An overwatered tomato appears wilted, with drooping leaves and yellowing. The soil feels constantly wet, and plant growth may be stunted.

Why Are The Leaves On My Tomato Plant Turning Brown And Black?

Leaves on tomato plants turn brown and black for various reasons like diseases, pests, insufficient watering, or environmental factors. Proper care, regular watering, and disease monitoring can help prevent this issue.

How Do You Stop Tomatoes Going Black?

Ensure tomatoes are correctly stored in a cool, dry place to prevent them from turning black. Avoid exposing them to direct sunlight or extreme temperatures. Additionally, handle them with care to avoid bruising.

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