Yellow Leaves on Tomato Plants: Causes & Treatments

Many people wonder how to fix the issue of yellow leaves on tomato plants. In fact, yellow leaves on tomato plants are very complicated because there are several types of problems that cause yellow leaves.

Here is a description of the most common problems with yellow leaves on tomato plants and their solution.

Why Are the Leaves on Tomato Plants Turning Yellow?

Why Are the Leaves on Tomato Plants Turning Yellow? Chlorosis in tomato plants or the appearance of yellow leaves on tomato plants is a very common symptom once the plant starts to develop and emit its first flower bunches.

However, it is not always due to a single cause but to a sum of variables, such as lack of nutrients, pest and disease activity, or atmospheric conditions (cold, drought stress, or lack of lighting).

In this article, we will highlight the main causes of yellow leaves on tomato plants, as well as their possible solution.

Yellow Leaves on Tomato Plants due to Irrigation

Excess Water

Yellow leaves on tomato plants due to excess of water: The leaves look yellow and pale, apart from the fact that you know perfectly well how often you water your tomato plants. Excess water causes the roots to rot (little by little) and can also cause fungus.

How to fix yellow leaves on tomato plants due to excess of water: If you have a pot, and you can put drainage without suffering the plant, well, if not you already know for the next time. If it is a pot or container, check that it has holes in the bottom and raise the container a few inches off the ground, so the water will be eliminated little by little. You can also add sand to the substrate to absorb excess water.

Lack of Water

Now let’s go to the opposite of the above.

Yellow leaves on tomato plants due to lack of water: The leaves dry out and some of them are crunchy.

How to fix yellow leaves on tomato plants due to lack of water: Water with more water and more regularly, remember that the water must penetrate to the root so that it can be absorbed. Also, try to avoid the hottest hours of the day, you may water correctly, but most of it will evaporate.

Yellow Leaves on Tomato Plants due to Lack of Light

Yellow leaves on tomato plants due to lack of light: The tomato leaves look discolored and decayed. Keep in mind that the ideal is 5 hours of sun for tomato plants, so that the tomatoes evolve correctly, although with some less they also develop.

To fix this problem, change the location of your tomato plants. If they are planted in the ground, and already have a flower, forget you should not repot it because surely, you will ruin the fruit, and it is not worth it, try to pamper them so that they evolve and give fruit in the place you have them and for the next plantation you already know to write it down.

yellow leaves on tomato plants lack sun
Tomato plant with burned leaves.

Leaf-eating Insects

Usually, under the tomato leaves, there are small insects that devour the leaves or suck the sap, leaving it yellow until it becomes transparent.

Use an ecological insecticide such as Neem oil, or you should apply potassium soap. This will eliminate the insects that cause yellow leaves on tomatoes.

Yellow Leaves on Tomato Plants due to Lack of Nutrients

Yellow leaves on tomato plants due to lack of nutrients. Nutrients are very necessary and in many cases, you will have to incorporate them. This happens a lot when you grow in containers such as grow tables or pots and the plant consumes the nutrients before the fruit ripening cycle is finished. Learn more about Nutrient Deficiency in Plants.

tomato plant lack of nutrients
Yellow leaves on tomato plants due to lack of nutrients.

Lack of Nitrogen

Nitrogen deficiency presents itself with a generalized lack of growth and problems in sprouting. Yellow leaves on tomato plants appear all over the plant, both young and adult leaves. Plant stunting reveals nitrogen deficiency compared to other element deficiencies.

Lack of Magnesium in the Orchard

Magnesium deficiency is manifested by a yellowing of the old leaves, keeping the nerves green. It is usually common in acid soils with a sandy texture, especially when high amounts of potassium are applied and in cold and humid periods.

yellow leaves tomato plants lack nitrogen magnesium
Yellow leaves on tomato plants due to a lack of nitrogen and magnesium.

Lack of Sulfur

Sulfur deficiency is quite rare to observe since many fertilizers contain this element in their composition. It starts with yellow leaves on young tomato leaves, much like nitrogen, and appears in very heavy soils with low oxygenation.

Lack of Potassium

Potassium deficiency also causes yellow leaves on tomato plants, starting on adult leaves and edges. As the deficiency progresses, necrotic spots form and form wounds. It can occur in soils of acid pH and sandy texture, with high magnesium content and high fruit load.

yellow leaves tomato plants lack sulfur potassium
Yellow leaves on tomato plants due to a lack of sulfur and potassium.

Lack of Zinc

Zinc deficiency in tomatoes creates chlorosis in the midrib in the form of spots or thickened spots, resulting in a chlorotic halo on a dark-colored leaf. This chlorosis in tomatoes usually occurs in high pH, phosphorus-rich soils, and cold conditions.

Lack of Iron

Iron deficiency in tomatoes is quite frequent, starting with chlorosis in the leaflet and leaving the nerves green. Subsequently, it ends in completely yellow leaves. Iron chlorosis usually occurs in soils with an alkaline pH, calcareous type, and low oxygenation.

Learn more about What is ferrous sulfate iron used for?

yellow leaves tomato plants lack zinc iron
Yellow leaves on tomato plants due to a lack of zinc and iron.

Phytotoxicity on Tomato Plants

Phytotoxicity in tomato plants is the result of causing leaf burn by an inappropriate nutrient mixture. There are some incompatible mixtures in foliar treatments that cause leaf problems, such as mixing mineral oils and coppers or sulfurs.

On the other hand, not controlling the pH in the foliar treatment and having an excessively acidic application mixture can also create phytotoxicity due to excess acidity. The result is generalized chlorosis, where yellow leaves are observed in tomatoes, in some cases with small brown spots.

However, yellow leaves on tomato plants are quite different concerning nutritional deficiencies. In this case, concentrated spots are observed in the form of dots or a superficial type, as if they had been burned.

Solution: There is no solution for phytotoxicity on already affected tomato leaves. The only thing we can do is to encourage the sprouting of new leaves and energetically stimulate the tomato plant. It is common to use a fertilizer suitable for tomato plants.

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JR Peters 51324 Jack's Classic 12-15-30 Tomato Feed, 1.5 lb.
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Conclusions About Yellow Leaves on Tomato Plants

The treatment of pests, diseases, or yellow leaves on tomato plants is very focused on the experience. Once you have the experience of growing tomatoes for several seasons, you will detect the problem at a glance. I hope this guide about yellow leaves on tomato plants is helpful to identify problems in your tomato plants, fix them and have a great crop.

If you are interested in learning more about tomatoes, we recommend the following articles about tomatoes:

Leaves Curl Up on Tomato Plant – 5 Reasons

Prune Tomato Plants: How to Prune Tomato Plants for Maximum Yield & When

How to Grow Hydroponic Tomatoes

How To Fertilize Tomatoes – Big Tomatoes

yellow leaf tomato
Leaves turning yellow on tomato plants.
About Henry Morgan

We are the Morgan family, Henry, and Julia, both agronomists from the University of Michigan, where we met. We are experts in putting our hands in the soil and developing organic foods and improving production processes for decades. Likewise, we have worked for companies such as Mondelez International, BASF, Monsanto, etc. currently in our role as science writers for TheGardenStyle.com as well as advisors in promoting large scale food growing in urbanized areas. In this website, we share what we are most passionate about, gardening and farming. Enjoy and see real photos on our website.