Sunflower Leaves Turning Brown- 7 Proven Reasons

Sunflower Leaves Turning Brown

Helianthus annuus (sunflower) is the most loving summer-time plant. Its yellowish petal with the seeds in the middle is truly eye-catching. But here is one you need to know about sunflower plants. In the whole plant kingdom, Helianthus annuus is one of the most sensitive plants we grow in our gardens.

You can’t water the plant at any time you want neither put it anywhere. You have to take care of it like your child. Otherwise, you will lose the plant. You must have encountered sunflower leaves turning brown, but do you know the reason why do so? 

Why My Sunflower Leaves Turning Brown- 7 Proven Reasons

There are many reasons that why sunflower plant leaves turn brown. Below we have discussed the seven leading reasons. Scroll down the article to read.

1.    Beetle Damage

Are you sure that the brown spots on the sunflower leaves are spots, not an insect? Yes, you heard it right. If you look closer at the points, you will see that they are moving. Beetle is a common sunflower insect frequently found in the US.

Beetle is a silent eater of sunflower leaves. The brown head white body insect size is around 1/4 inches. The season for the beetle to attack sunflower leaves is summer and spring. They chiefly attack young plants.

Are you thinking about how you can prevent beetle production on the leaves? All you need to do is to use organic insecticide. The organic insecticide will prevent the beetle formation and will help the plant to grow well.

2.    Leaf Diseases

There can be many reasons for sunflower leaves diseases. The common reasons for disease formation are climate change and an excess amount of PH in the soil. Along with that, pathogens also favor the formation of diseases on the sunflower leaves. 

Pathogens attack the sunflower plant at the stage of seedlings. As per time, the pathogens remain inside the body of the plant, grow gradually. Once the plant matures, they start to show brown spots on the leaves. 

If the affected plant does not cure, then the disease can spread in the whole colony, and in the end, the plant will die. Use organic fungicides to kill the pathogens present inside the soil and body of sunflower plants.

3.    Septoria Leafspot

Want to know about another fungus that is living under your nose without letting you know? Well, fungus septoria is another silent eater of sunflower leaves commonly found in gardens. 

But do you know what promotes its growth? The mistake most gardeners do they grow the seeds without checking at either they are fungus-free or not. Fungus septoria infects the sunflower at a young age. 

To identify the fungus septoria, closely examine the brown spots on the leaves. The size of the places will be around 1/4-1/6 inches with dark brown margins. To skirt Fungus septoria formation, use disease-free seeds, keep the garden clean, and avoid overwatering the plants.

4.    Glassy-winged Sharpshooter

Without a doubt, the sunflower plant is an eye-catching beauty. But what do you think? Does it is eye-catching only for humans? Definitely not! More than humans, insects are way attracted to the sunflower plant. Here is another insect whose favorite host is the sunflower “Glassy-winged Sharpshooter.”

Glassy-winged Sharpshooter is a shiny brown insect with black wings at its back. This insect loves to lay eggs on the leaf tissues. When the eggs hatch, they leave brown spots on the leaves. 

Glassy-winged Sharpshooter itself does not harm the sunflower plants. However, it is a vector of Xyella Fastidiosa bacterium. This bacteria is dangerous for the sunflower plant.

5.    Downy Mildew

According to scientists and expert gardeners estimation, Downy mildew is one of the most dangerous sunflower plant diseases. Do you know the reason why they say so? Because this disease not only affects the leaves but also affects the buds and stem of the plant.

Downy mildew is a fluffy soft mass present on the underside of the sunflower leaves. The curing process of Downy mildew is pretty simple. You have to use copper organic fungicide for around 7-10 days. After that, the results will be visible. Humid weather promotes its growth.

Downy mildew belongs to the fungus family of Peronosporaceae. Its affected color ranges from light brown to purplish to grey. 

6.    Rust Disease

Rust is a common plant disease. Not only sunflowers but other plants like wheat, beans, maize, sugarcane, blueberry, and groundnuts are also affected by this powerful pathogen fungus.

Controlling rust is not a cup of tea. Once this pathogenic fungus starts to grow, it eats the whole colony, leaving only dead plants behind. There is no specific season for this disease to spread. It can open at any time throughout the year.

To control rust formation, first, you need to lessen the moist in the soil. Humid is the medium in which rust spreads quickly. Now pinch off 1/3 part of the affected sunflower leave at one time. After taking a short interval, pinch off 1/3 again, and keep repeating the same process.

7.    Fungal Wilting

Here is the last reason that why sunflower plant leaves turning brown? So far in this gardening journey, you must have noticed that sunflower plants are climate-sensitive. The moment weather changes from summer to spring, the leaves will start to wild or die maybe.

In this sensitive situation, fungus plays an active. It uses hawk’s eyesight to detect which sunflower plant is getting weak and attack it immediately. First, the fungus attack soil and then slowly start to the whole plant.

When the fungus reaches the leaves, it starts to leaves brown spots on them. The most dangerous point about this disease is there no such quick and effective solution. If any young plants are affected, then you have to remove them safe the colony.

How to Prevent Sunflower Leaves Turning Brown- Ultimate Care Guide

Helianthus annuus (sunfloweris a sensitive plant. Your single mistake can ruin the whole colony. Since we have learned that cause the sunflower leaves to turn brown, now is the time to learn how we can prevent it from happening.

Choose High-Quality Soil

The first thing is the choice of the best soil. Sunflower plants demand high-quality soil, and you have to fulfill their demand. The soil should be loose to allow the plant to grow roots deeply. 

Strong wind and excess water intake can effortlessly weaken its foundation. That is why choosing high-quality soil is a must. Sunflower can not grow until its taproots reach the depth of the earth.

Proper Planting

That also matters that how deep you are planting the plant. You need to dig a deep hole about 2-3 inches deep. Never grow the sunflower plants too close to each other. Do you know the reason why? Because sunflowers too close to each other will block the airflow.

If you have bouquet-sized blooms of sunflower, then plant them 6-inches apart from each other. Or if you have a large variety of sunflowers, then distance them about 12-inches away.

Provide Adequate Amount of Sunlight

We accept that sunflowers are sun-loving summer plants, but that does not mean that you can keep under sunlight as much as you want. Do provide them direct sunlight but in an adequate amount.

Keep the sunflower under direct sunlight for about 6-7 hours. More or less than this figure will not help the plant to bloom well. At 6-7 hours timing, the sunflowers will bloom well.

Don’t Over Water

Here is the main caring factor. Are you sure that you are watering the plant in an adequate amount? Not or less nor high? Keep in mind that humid is the medium that promotes sunflower disease production.

At a young age, water the plant daily 3-4 inches away from its stem. At this age, sunflowers do need liquid to grow. After the sunflower plants mature, water them only once a week because they have a high-heat tolerance capability.

Fungicide and Pesticide

Here is the last but the most crucial factor. No matter if you plant the sunflowers properly, water them in an adequate amount, and even provide them direct sunlight. But if you do not supply them with fungicide and pesticide, all your effort is useless.

Fungicides and insecticides prevent diseases and pests production near the plant. They kill the incoming danger naturally without letting them harm the plant. Do use organic fungicide and pesticide to enjoy the best results.


Sunflower is the most loving summer plant. Proper care and some strategies can help you to grow healthy sunflower plants. Without a doubt, the brown spots on the sunflower leaves spoil the overall look of the plant.

The last piece of advice for you is to avoid over damping the soil. Water the plant at a young age and once a week at the maturation stage.

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