Photo showing yellow leaves on tomato plants

Yellow Leaves on Tomato Plants: A Helpful Guide to Preventing Issues

You’ve lovingly tended to your tomato plants, but suddenly the leaves are starting to turn yellow.

We’ve been there and know this common problem can dampen the spirit of any gardener, whether you’re a seasoned pro or a budding enthusiast. The most common cause of yellow leaves on a tomato plant is either a nutrient deficiency or disease. 

But here’s the good news: Understanding the root cause of yellow leaves on tomato plants is the key to solving this puzzle. In this guide, we’ll walk you through the common reasons for this problem, from overwatering to pests, and how each issue affects your plants. Then, we’ll arm you with effective, easy-to-implement solutions to not only address the current yellowing but also prevent it in the future.

Nutrient Deficiencies That Cause Yellow Leaves 

Yellow leaves on your tomato plants can be triggered by various nutrient deficiencies. By identifying the specific deficiency, you can take appropriate action to correct it and help your plants thrive. Let’s take a look at five common nutrient deficiencies that cause yellow leaves.

Nitrogen Deficiency

If your tomato plant’s leaves are turning yellow, especially the older ones near the base, this could be due to a nitrogen deficiency. Nitrogen is essential for leaf growth and overall plant health, so it’s important to address this issue promptly. To fix a nitrogen deficiency, you can add nitrogen-rich fertilizer or amendments like aged manure or blood meal.

Magnesium Deficiency

A magnesium deficiency can manifest as yellow leaves with green veins, usually starting with the older leaves. Magnesium plays a crucial role in photosynthesis, so addressing this deficiency is important for plant growth. To correct a magnesium deficiency, you can spray a solution of Epsom salts (magnesium sulfate) or apply magnesium-containing fertilizers to the soil.

Iron Deficiency

Iron deficiency (also known as chlorosis) leads to yellowing of young leaves with green veins, as iron plays an important role in chlorophyll production. This can sometimes happen if your soil is too alkaline or there is insufficient available organic matter. To address iron deficiency, you can try adding iron sulfate to the soil or use a foliar spray containing iron chelates.

Potassium Deficiency

In the case of potassium deficiency, leaf edges and tips can turn yellow and show signs of burning or necrosis. Potassium is vital for transporting nutrients and water within the plant and resisting diseases. To correct this deficiency, use a potassium-rich fertilizer, or add wood ash or kelp meal to your soil.

Calcium Deficiency

Lastly, a calcium deficiency can cause yellowing of new leaves, and often results in leaf tip burn or blossom end rot on fruits. Calcium is crucial for the development of cell walls in plants, and ensuring adequate calcium levels is important for overall plant health. To address a calcium deficiency, you can add gypsum or lime to the soil, or use a calcium-rich foliar spray.

Remember, it’s always a good idea to test your soil before amending it, to ensure you’re addressing the appropriate deficiency and not worsening the problem.

Diseases Causing Yellow Leaves

If your soil test shows no sign of a nutrient deficiency, there is a good chance disease may have crept in. Let’s take a look at some of the most common diseases that cause your tomato leaves to turn yellow. 

Early Blight

Early blight, caused by the fungus Alternaria solani, could be responsible for your tomato plant’s yellow leaves. This disease typically starts at the lower leaves and gradually progresses upward. You may notice dark brown spots with concentric rings, causing the leaves to yellow and eventually drop off. To combat early blight, remove affected leaves and avoid overhead watering. Applying fungicides can also help prevent its spread.

Fusarium Wilt

Another common cause of yellow leaves on tomato plants is Fusarium wilt. This soil-borne fungal disease targets the vascular system of your plants, causing leaves to wilt and turn yellow. You’ll usually see the symptoms on one side of the plant first. To prevent Fusarium wilt, practice proper crop rotation and choose resistant cultivars.

Septoria Leaf Spot

Septoria leaf spot, caused by Septoria lycopersici, is another fungal disease that could lead to yellowing leaves. This disease presents as small, water-soaked spots that later develop into yellowish or gray centers with dark borders. Proper sanitation, such as removing affected leaves and avoiding overhead watering, can help prevent Septoria leaf spot. Fungicides can also be used if necessary.

Verticillium Wilt

Verticillium wilt may be the culprit behind your yellow tomato leaves. This soil-borne fungus can attack the xylem of your plants, causing stunted growth, yellowing, and eventually browning of leaves. The best course of action is to select resistant varieties and practice good sanitation, such as rotating crops and removing plant debris from the garden.

Late Blight

Late blight, caused by the water mold Phytophthora infestans, can also cause yellowing and eventual death of your tomato plant leaves. Leaves may develop grayish, water-soaked spots that eventually turn brown and have a fuzzy appearance. This disease spreads rapidly, especially in wet and cool conditions. Treatment options include removing affected plants, applying fungicides, and choosing resistant varieties.

By familiarizing yourself with these common diseases causing yellow leaves on your tomato plants, you can address the issues promptly and help your plants thrive.

Pests Affecting Tomato Plants

Tomato plants, like any other plants, are susceptible to various pests which can cause damage and lead to yellowing leaves. In this section, we will cover some common pests that attack tomato plants and how you can deal with them.


Aphids are small, soft-bodied insects that feed on plant sap, causing leaves to curl and turn yellow. To control aphids, you can:

  • Spray your plants with a strong water jet to dislodge the insects.
  • Apply insecticidal soap or neem oil to the affected areas.


Thrips are tiny, slender insects that pierce tomato leaves and suck out the sap, resulting in yellow, speckled leaves. To manage thrips, you can:

  • Remove any affected leaves and dispose of them properly.
  • Use sticky traps to monitor and reduce their population.
  • Introduce beneficial insects, such as ladybugs and lacewings, to prey on the thrips.

Spider Mites

Spider mites are nearly microscopic pests that create fine webs on the underside of tomato leaves. They feed on the leaves, causing them to turn yellow and dry up. To control spider mites, you can:

  • Keep the area around your tomato plants clean and free of debris.
  • Spray the affected plants with a miticide or insecticidal soap.

Flea Beetles

Flea beetles are tiny black or brown insects that jump like fleas when disturbed. They chew small holes in tomato leaves, leading to yellowing and even defoliation. To protect your plants from flea beetles, you can:

  • Use floating row covers to prevent beetles from reaching your plants.
  • Apply Diatomaceous earth or a botanical insecticide to control the beetles.


Hornworms are large, green caterpillars that feed on tomato leaves and can cause significant defoliation. To manage hornworms, you can:

  • Handpick the caterpillars from your plants and dispose of them.
  • Use Bacillus thuringiensis (Bt), a biological control, to target hornworms without harming beneficial insects.


Cutworms are brown or black caterpillars that feed on the stems and leaves of tomato plants, causing them to wilt and potentially die. To prevent cutworm damage, you can:

  • Place a collar around the base of your plants to act as a barrier.
  • Keep the area around your plants well-cultivated to disrupt their life cycle.

Other Causes of Yellow Leaves

Apart from nutrient deficiencies and diseases, there are several other factors that can cause yellow leaves on tomato plants. 

Incorrect Watering

Proper watering is crucial for the health of your tomato plants. Providing too little water can cause the leaves to yellow, while excessively watering can lead to root rot or fungal issues. To maintain a balanced watering schedule, water your plants deeply and consistently, allowing the soil to dry slightly between waterings. Also, make sure to water early in the day to prevent water evaporation and to cut down on diseases that thrive in damp conditions.

Soil Compaction

Compacted soil restricts the roots’ access to essential nutrients, water, and air, which can make your tomato plant’s leaves turn yellow. To address this issue, you can try loosening the soil around your plants using a garden fork or cultivating tool. Adding organic matter, such as compost or well-rotted manure, can also improve soil structure and promote healthier root development.

Herbicide Damage

Herbicides used near tomato plants can accidentally cause harm to their leaves. Drift from nearby applications or residues in the soil can lead to yellowing leaves and twisted growth. To prevent this, use caution when applying herbicides and follow the product’s label instructions carefully. Avoid applying herbicides on windy days, and consider covering your tomato plants with protective barriers.

Transplant Shock

Transplant shock occurs when tomato plants experience stress during the transplanting process. This can cause a variety of symptoms, including yellowing leaves. To minimize transplant shock, harden off your seedlings, gradually exposing them to outdoor conditions before transplanting. Additionally, choose a cool, cloudy day for transplanting to help reduce stress and ensure that the plants receive adequate water to help them establish themselves in their new location.

Sunlight Deficiency

Tomato plants need adequate sunlight to thrive and produce fruit. Without enough light, leaves may turn yellow as the plant struggles to photosynthesize. Make sure you plant your tomatoes in a location that receives at least 6 to 8 hours of direct sunlight each day. If you’re growing tomatoes indoors or in an area with limited sunlight, consider using artificial grow lights to provide them with the necessary light.

Nutrition and Soil Management

To ensure your tomato plants have healthy, green leaves, it’s crucial to focus on proper nutrition and soil management. In this section, we’ll explore the importance of testing soil pH, using compost, and correct fertilizing practices.

Testing Soil pH

To determine the nutritional needs of your tomato plants, it’s important to test the soil pH. A proper pH balance ensures that your plants can effectively absorb essential nutrients from the soil. You can use a soil test kit to measure the pH levels in your garden. Typically, tomato plants thrive in slightly acidic soil with a pH of 6.0 to 6.8. If the pH needs adjusting, consider using lime to raise it and sulfur to lower it.

Using Compost

Incorporating organic matter like compost into your garden soil can improve its texture, water retention, and overall health. Compost adds vital nutrients that support the development of strong tomato plants. Here’s how you can use compost in your garden:

  • Spread a layer: Before planting, spread a 2-3 inch layer of compost over the planting area.
  • Mix it in: Gently mix the compost into the top 4-6 inches of soil, ensuring an even distribution.
  • Top-dress: Throughout the growing season, add a thin layer of compost around the base of your tomato plants to provide extra nutrients and improve soil structure.

Correct Fertilizing

Proper fertilizing is essential for your tomato plants to produce healthy leaves and bountiful fruit. Over- or under-fertilizing can lead to yellowing leaves and poor fruit production. To properly fertilize your tomato plants, follow these steps:

  • Choose the right fertilizer: Look for a balanced tomato-specific fertilizer that contains nitrogen, phosphorus, potassium, and essential micronutrients.
  • Apply at the right time: Fertilize your tomato plants at planting time and then again when the first fruits appear. Additional applications may be needed during periods of heavy fruit production.
  • Follow application instructions: Always adhere to the manufacturer’s recommendations regarding fertilizer amounts and application methods to prevent nutrient imbalances.

By paying close attention to soil pH, using compost, and properly fertilizing, you can provide your tomato plants with the nutrients they need to grow strong and healthy, reducing the likelihood of yellow leaves.

Best Practices for Prevention

To maintain healthy tomato plants with green leaves and a high yield, it’s important to follow some preventive measures. By doing so, you can prevent yellow leaves and other issues that may impact your tomato crop. Here are some best practices to implement in your gardening routine:

Firstly, practicing crop rotation is an effective way to minimize the risk of soil-borne diseases and pests. This involves changing the location of your tomato plants in your garden each year. By doing so, you can disrupt the life cycles of pests and pathogens, promoting healthier plants and reducing the occurrence of yellow leaves.

Proper watering is essential for maintaining the overall health of your tomato plants. Overwatering and underwatering can both lead to yellow leaves. Make sure to water your plants consistently, providing just enough moisture without causing waterlogged soil. Invest in a soil moisture meter to help you monitor the water levels in your soil.

Ensure that your plants receive sufficient nutrients by feeding them with a balanced, all-purpose fertilizer. Nutrient deficiencies can cause yellowing leaves, so monitor your plants and make any necessary adjustments to their feeding schedule. Potassium and phosphorus deficiencies are especially important to address since they can lead to yellow or brown spots on leaves.

Selecting healthy plants from the start helps establish a strong foundation for growth. When purchasing seedlings, choose plants with green leaves, strong stems, and no signs of diseases or pests. Additionally, maintain a clean garden by promptly removing fallen leaves and debris, as these can harbor diseases and pests that may attack your tomato plants.

Finally, proper spacing between your tomato plants is crucial for their well-being. Overcrowding can lead to poor air circulation, making your plants more susceptible to fungal diseases that can cause yellow leaves. By giving your plants enough space to grow and ensuring adequate air circulation, you’ll promote a healthier environment and higher yield for your tomato crop.

By following these friendly best practices, you can prevent yellow leaves on your tomato plants and enjoy a bountiful harvest.

Frequently Asked Questions

Why are the tips of my tomato leaves turning yellow?

The tips of your tomato leaves could turn yellow due to numerous causes such as inconsistent watering, nutrient deficiencies, and plant diseases. Make sure you are watering your tomato plants evenly, providing the essential nutrients, and observing the plants for signs of disease.

What causes brown spots on tomato leaves?

Brown spots on tomato leaves could indicate a fungal or bacterial infection. To avoid this issue, keep your tomato plants well-spaced. Proper spacing allows adequate air circulation and reduces the spread of diseases. Remove the affected leaves, and consider using a fungicidal spray if the issue persists.

How can I help my tomato plant after its leaves turned yellow from transplanting?

After transplanting, tomato plants need some time to adjust to the new environment. To help them recover, keep the soil consistently moist but avoid overwatering. Provide them with adequate sunlight and ensure balanced nutrition by using a balanced fertilizer.

Are yellow spots on leaves caused by a nutrient deficiency?

Yes, yellow spots on tomato leaves can be caused by a nutrient deficiency, particularly nitrogen deficiency. To resolve this issue, consider adding some organic matter to the soil and apply a nitrogen-rich fertilizer.

How can I prevent the bottom leaves of my tomato plant from dying?

To prevent the bottom leaves of your tomato plant from dying, maintain consistent watering, improve soil drainage, and trim off any dead or dying leaves. Pruning helps promote healthy growth and minimizes the risk of diseases.

What’s the proper watering technique to avoid yellowing leaves in tomato plants?

To avoid yellowing leaves, ensure correct watering techniques. Water your tomato plants deeply and consistently, ideally during the early morning hours. Avoid waterlogging and allow the soil to dry between watering sessions. Using mulch can help maintain soil moisture and prevent overwatering.

Final Thoughts

Remember that yellow leaves on your tomato plants aren’t just a setback but a signal and an opportunity to deepen your gardening expertise. By understanding the underlying causes – be it water issues, nutritional imbalances, or pest invasions – you’re now equipped to respond effectively and prevent future occurrences.