Yellowing Tomato Plant Leaves: 5 Common Causes and Solutions

Tomato (Solanum Lycopersicum) is one of the most loved crops for home gardeners and beginners. It is also one of the most troublesome crops that can host several pests and diseases, so it is considered a “heavy feeder.”

Several factors can cause tomato leaf discoloration. Sometimes, the problem is natural and not a cause of worry, and other times you need to pay close attention. Yellow tomato plant leaves are ubiquitous with lots of potential solutions.

They can be signs of many problems ranging from nitrogen deficiency, underwatering, herbicide damage, fungal diseases, etc. Since you want to treat yellow tomato plant leaves, note that a few yellow leaves on tomato plants are usually nothing to worry about.

Why Are My Tomato Plant Leaves Turning Yellow?

yellow tomato plant leaves

There are several reasons why tomato plant leaves turn yellow; most of them can be rectified, while the rest require extra measures. It can also indicate something as simple as too much water or something serious like a pest attack.

Below are some of the reasons why your tomato plant leaves may turn yellow:

1 . Overwatering And Fusarium Root Rot

The most common cause of yellowing leaves on tomato plants is overwatering. The plant needs perfect soil moisture levels and shouldn’t be too wet, not too dry.

It would help if you determined how much water is needed by taking your weather conditions and the soil type, and the level of mulch you use into account. Root rot is one of the possible outcomes if you tend to overwater potted tomato plants or if your garden has soil that does not drain well.

When the roots of your tomato plant are flooded for extended durations, they tend not to breathe anymore. This is due to a lack of oxygen that causes the plant tissue to die and eventually decay.

2. Disease

Another cause of yellowing leaves in tomato plants is a disease. Tomato Plant disease causes yellow leaves, most of which can be challenging to tackle once established. The first signal is early blight, and a fungus in the soil causes this.

Luckily, thus the problem is easy to spot, and when infected, the lower leaves of the tomato plant show symptoms like a pale yellow spot that turns into a dark patch with yellow at the edges. If left untreated, the entire leaf will turn yellow and drop off.

Another disease that affects tomato plant leaves is the Septoria Leaf Spot. When infected, tomato plants will display large brown spots in their leaves connected by patches of yellow. 

If this symptom is left untreated, the disease can move from the leaves to the plant’s stem and cause more damage. When you notice affected leaves, ensure you keep them away from other plants in your garden. Apply fungicide designed to treat the diseases and do well to follow instructions on the product exactly how it is. 

3. Nitrogen Deficiency

Nitrogen is essential for plant growth and chlorophyll. When nitrogen is deficient in tomato plants, the older leaves at the bottom turn yellow, and the upper new leaves remain the same, bright green as though there’s no problem. 

Nitrogen deficiency can be caused by sandy soils, drought, high rainfall, and mowing organic matter. Before adding nitrogen to the soil, consider amending it with compost manure, urea, or ammonium.

4. Transplant Shock

Transplant Shock is also a common cause of yellow leaves in tomato plants. Transplant Shock usually occurs when you’ve recently transplanted your seedlings about a week or two before or when you notice yellowing leaves on the bottom of the plant.

The shock is not usually detrimental to the plant but can cause the bottom few leaves to be yellow. However, it is just a short adjustment phase, and as long as the new growth is green and heavy, there is no cause for alarm.

The yellow leaves will drop off, and the plant will return to good health. If you notice signs of transplant shock, you can quicken the plant’s recovery by removing the yellowing leaves at the stem. This way, energy will be directed toward the new growth and prevent the leaves from drying.

5. Fungal Wilt

When your tomato plant is infected with fungal wilt, you will see yellow splotches and brown veins on the leaves. To prevent this, planting in well-drained soil is considered the best.

Also, if you notice yellowing leaves on one side of your tomato plant followed by wilting and browning leaves, it may be suffering from Fusarium wilt.

Fusarium wilt is a soil-borne fungus that infects stems and leaves and causes a restriction in water that leads to yellowing tomato leaves. It can also survive in the soil for years, and it’s most detrimental in soil temperatures approaching 80 degrees.

6. Tomato Yellow Leaf Curl Virus

Symptoms of the tomato yellow leaf curl virus may include stunted growth of leaves, yellow leaf margins, upward curling of leaves, etc. The tomato plant leaves drastically lessen fruit yield. If infected early in the season, the plant may not produce any fruit.

Ways To Treat Tomato Plant Leaves Turning Yellow

1 . Proper Watering Patterns

Proper watering is essential for the health of your tomato plants. Always check the soil daily and only water when the plants need it; that is when the top 1 or 2 inches of the soil has dried.

Also, water in the mornings prevents evaporation and damage to the leaves. Most Importantly, apply water to the soil around the roots and not the leaves. Gentle water the leaves deeply to thoroughly saturate the soil and encourage profound root growth.

2. Buy Healthy Plants

While purchasing tomato plants from a local garden center, be sure to look out for healthy plants, the ones with stocky growth, green leaves free of spots or yellowing. Unhealthy plants tend to introduce pest and disease problems which can take years to eliminate from the garden.

3. Avoid Herbicides

Tomato plants are sensitive to synthetic, organic, or homemade herbicides. Herbicides can damage plants resulting in stunted yellow growth.

4. Plant Varieties Of Tomatoes That Are Blight Resistant

Remove affected leaves and add a mulch of straw to the base of the plant. Also, using tomato stakes and cages helps keep tomato leaves off the ground and away from potential water or soil-borne contaminants.

In addition, you can also protect your tomato plant leaves by using a soaker hose that waters the plant at their base rather than overhead watering, which causes more splashing and cross-contamination.

5. Prevent Fertilizer Burn

When fertilizing your tomato plant, ensure you follow the directions on the product label. This will allow your plant to get the nutrients they need with limited fertilizer runoff or damage to your crops.

Frequently Asked Questions

1 . What Is The Best Fertilizer For Tomato Plants?

Use a simple fertilizer formulated for tomatoes, usually with a ratio of 3-4-6 on 4-7-10. However, most gardeners prefer to use a high phosphorus fertilizer.

2. What Does Epsom Salt Do For Tomatoes

Epsom soil aids germination, early root and cell development, photosynthesis, and plant growth.

3. Do Coffee Grounds Help Tomato Plants?

Coffee grounds contain 2% nitrogen, essential for plant growth and chlorophyll. It also contains moderate amounts of phosphorus and potassium.

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