Sunburn Tomato Leaves – What Does it Mean and How to Prevent

If you’re experiencing burns on tomato leaves in your plantation or home garden, then this guide is for you.

This issue was a frustrating one to me when it invaded my plantation. I couldn’t get rid of the burns on the tomato leaves on my plantation. For me, the issue was over-exposure of the plant and its seedling to sunlight leading to high exposure to heat, and its leaves are heat stressed. While some other gardeners have similar issues as mine, the causes of the burn on the tomato leaves differ for others.

After several studies and engagement with other tomato gardeners in forums online, I was able to find solutions. 

Today I will share how I overcame this issue and tips from other tomato gardeners who had similar issues.

In this article, I will show you what it means to have burns on your tomato leaves, their causes, how to prevent it, and how to care for the tomato plant if you already have a tomato leave burn.

Let’s dive in!

Tomato (Solanum lycopersicum) are sun-loving flowering plants from the nightshade family. Wide varieties of tomatoes are grown in different regions worldwide, with their taste ranging from sweet to sour. Tomatoes are among the most popular fruit vegetable plants grown globally in-home gardens.

Tomatoes are easily grown and need proper care and maintenance for optimum yield. Some basic agricultural practices for crop production must be followed to achieve an abundant harvest from your tomato garden. 

When these practices are not properly carried out, external factors such as; soil moisture, weed, temperature, and soil mineral matter may affect your plant’s growth. 

Sunburns are caused by the external factor affecting tomato yield. The good news is that you can control some of these external factors and prevent further damage to your tomato plant.

Meaning of Sunburned Leaves

Sunburn on tomato leaves means the tomato leaves can’t undergo photosynthesis. It is characterized by white or yellow patches on plant leaves. Photosynthesis is an essential chemical process all green plants and vegetables undergo to produce sugar, a feeding mechanism for them.

This coloration alters the leaves’ photosynthetic processes because photosynthesis only occurs in the green plant’s chlorophyll. 

Sunburn causes irreversible damage to the affected tomato plants, so they don’t have enough chlorophyll to produce enough nutrients for growth. The color of severely sunburnt tomato leaves will change to crispy brown around the edges; the leaves then wilt and fall off.

Causes of Sunburned Tomato Leaves 

Identifying the primary cause of sunburn on my tomato leaves helps me to figure out the appropriate measures to prevent further occurrence. It also guide me through implementing the proper agricultural practices to rectify my tomato plantation. 

Here are some of the significant causes of sunburn on tomato plant leaves.  

1. Heat stress

The rate of transpiration (water loss) in all plants must be equal to or less than the rate at which the plant absorbs water from the soil to maintain an equilibrium state in the plant. 

Ensure you raise your tomato seedlings in a shaded area (screen/greenhouse) before permanently transplanting them to the field. When the seedlings are transferred to the field or garden under direct sunlight without proper hardening practices (an adaptation practice to heat from sunlight), the leaves of the tomato plants will be burned by the scorching sun. This is because the seedlings have yet to adapt to intense sunlight and absorb enough water to regulate the water loss (transpiration). 

2. Excessive Fertilization 

Tomato plants are heavy feeders that require lots of soil nutrients to thrive well. Hence, fertilizer application is a great way to supplement the unavailable soil nutrient to meet your tomato`s soil nutrient requirements. While fertilizer application is vital to tomato plants, it should not be overdone because an excessive application can cause more harm than good. 

Improper or excessive fertilizer application practices may cause the edges of your tomato leaves to turn brownish, brittle, and dry off (sunburn). 

3. Overwatering or Underwatering 

Tomatoes are sun-loving plants that have little tolerance to over/underwatering. When you apply excess water to the plant, it struggles with transpiration. 

Consequently, when you supply too little water, lack of water will alter the photosynthetic activities of the plant. 

Moisture stress, especially from underwatering, may burn the leaves from their tips to the leaf margin and eventually wilting. Sunburn in tomato leaves due to moisture stress usually occurs in older leaves where the sun hits the hardest

4. Nutrient Deficiency 

Marginal necrosis is caused by potassium deficiency in tomato plants. It is characterized by the yellowing of plant leaves which begins at its margin and spreads outward toward the leaves edges. 

The yellow color will further turn brown until the leaves shrivel and fall off. Marginal necrosis due to potassium deficiency is usually regarded as sunburn. Identifying potassium deficiency as the leading cause of burnt tomato leaves will guide you to apply an organic fertilizer to rectify the situation. 

How To Prevent Sunburn on Tomato leaves 

Now that you know the major causes of sunburn in your tomato plant, it is best to prevent its further or future occurrence. Below are some of the needed cultural practices to prevent your tomato leaves from getting burnt by the sun, watering, or through nutrient deficiency. 

1. Proper Hardening Before Transplanting

Tomato seedling hardening is the process of gradually exposing the plants to outdoor environmental conditions before transplanting them to the open field. It is training the plant to withstand harsher conditions outside the shaded areas (screen/greenhouse) where the seedlings were raised. 

Don’t transplant your tomato seedlings directly into the field without gradually exposing them to outdoor weather conditions. Improper or lack of hardening of tomato seedlings is the primary cause of sunburn. 

Tomato seedlings raised in a greenhouse should be placed in a shaded area outside the greenhouse for 48 hours before transplanting them to the field or your garden. Tomato seedlings grown under open shades should be placed in an area with little protection from the sun for 48 hours before transplanting them to the field. 

Provide minimal sun cover for your tomato seedlings for 3-4 weeks after transplanting them to the field, especially in harsh temperate regions. This should be done to assist the plants in their struggle to maintain equilibrium between water absorption and transpiration. 

2. Appropriate watering 

Tomato detests excess watering and cannot survive without adequate moisture. Watering must be done moderately for optimum yield in tomatoes and to prevent leaf burns. Water the roots of your tomato plants 2-3 times per week. Check the soil around the tomato plant before watering; if the soil is still moist, skip watering for that day. Avoid pouring water on tomato leaves to prevent the growth of fungus diseases on the leaves. 

3. Proper fertilizer application 

Prepare the garden or field where you want to transplant your tomato seedlings a week before transplanting. The appropriate spacing for tomatoes planted on the field is 18-24 inches apart within a row. The rows should be spaced 36 inches apart. 

Adding organic manures to the field is recommended before transplanting your tomato. Dig holes 8-12 inches deep, depending on the length of your tomato seedlings, following the appropriate tomato spacing. Mix organic manure with the soil in the holes 3-5 days before transplanting the tomato seedlings to the field. With this initial practice, you might not need to add fertilizer to the tomato plants for their entire growing season.

 If necessary, apply nitrogen fertilizer as a monthly side dressing to the plant. The fertilizer should be applied 4-6 inches away from the plant roots to prevent burning. Water the plant thoroughly after each fertilizer application.

How to Treat Sunburned Tomato Plant

Sunburned tomato leaves cannot regain their greenish color. Cutting off the burnt part of the leaves is best to prevent further stressing the plant.

 If you leave the burnt leaves on the plant, the plant will continue to struggle to heal the affected leaves. This action will alter the tomato plant’s optimum growth, especially during its fruiting stage. 

If the burnt tomato leaves are on the open field or garden, cut off the burnt leaves and cover the plants with sunscreen to prevent further damage. You can use white polythene, cheesecloth, or any white piece of cloth to cover the plant. 


Tomatoes are exceptional vegetable fruit worth growing in your home garden. The fruit of tomato contains many nutritional values, not to mention its varying taste, making it an important part of many recipes. With proper management and care, the yield of tomatoes is always abundant.

 The leaves of your tomatoes getting burned are nothing to worry about. With this blog, you can identify the primary cause of sunburns and how to prevent them. Once you identify the cause, take the necessary measures to suppress further damage to other healthy tomato plants in your garden. 

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