Helianthus annuus, also known as sunflowers, are gorgeous looking. Their beautiful bright-looking yellow bloom is why they are called happy flowers. They are great for spicing up your garden and creating a relaxing atmosphere for anyone who sees them.

They are sensitive but relatively easy to grow. External factors such as moisture, soil pH, nutrients, and temperature, play an essential role in their growth cycle.

As a result, it is not unusual for a sunflower plant to develop problems like its leaves turning brown. In this article, we explore all the possible reasons for this and how you can stop it.

sunflower-gardenReasons Why Your Sunflower Leaves Are Turning Brown

1. Leaf Disease

Sunflowers are prone to different types of diseases, and there could be a couple of reasons for this. One of the reasons includes an excessively high soil pH.

It is therefore important that you find ways to bring it down to a slightly acidic level which the sunflowers usually prefer.

Additionally, diseased plants may attract pathogens that cause additional complications.

The pathogens remain there until the plant matures and cause the leaves to have brown spots. The disease can spread to the whole plant and cause irrevocable damage.

One of the ways to manage the presence of pathogens is by using an organic fungicide to get rid of them.

A change in the climate can also cause leaf diseases. For instance, high carbon dioxide levels and hot temperatures have a negative multiplicative effect.

dying-flower2. Fungal Wilting

Fungal wilting can arise as a result of insufficient watering of your plant. Note that your plant lacking water doesn’t necessarily mean it has fungal wilting, although the likelihood is quite high.

One way to know this is to observe the plant thoroughly. If, after a day or two of sufficient watering, it still has brown spots on the leaves, it is definitely fungal wilting.

fungal-hit-flowerThese fungi can attack the plant from top to bottom, causing leaves and stems to have brown spots. To prevent this, make sure your sunflower gets enough water, especially at a young stage.

However, the only solution for already infected plants is to remove them altogether. Also, discard the soil and do not use it again for growing other plants.

3. Septoria Leaf Spot On Sunflower

This is caused by a fungus called Septoria helianthus. They can attack your sunflower garden.

Younger sunflower plants are more prone to this kind of fungus, which is circular and angular in shape and can either be brown or gray and appear as water-soaked spots.

They do not show signs early and can be easily missed until it’s too late.

The disease spreads from the lower leaves to the upper ones. Spots then begin to come together to form a dead tissue area.

You can avoid this by checking if the seeds intended for planting are free from this fungus. This is because even dry seeds are highly susceptible.

This fungal growth can affect young over-watered plants and is likely to manifest during heavy rainfalls.

You can solve this problem by observing your plants from a young age to catch the early signs.

You should also prune the affected leaves and make sure to wash your hands before handling the unaffected ones. Another option is to make use of either organic or chemical fungicides.

4. Beetle Damage

Another reason why your sunflower might be turning brown, especially during summers, is due to insects like beetles. When you observe your plant closely, you may notice the spots moving.

They are not real spots but insects with brown heads and white bodies. A typical culprit is the carrot beetle.

This problem is more likely to arise with newly planted sunflowers. It’s not just the leaves but the roots that can also be affected.

Use beetle-specific insecticides or other broad range organic insecticides to eliminate this problem.

5. Glassy-winged Sharpshooter

This is another type of insect that can leave brown spots on the leaves of your sunflower plant.  They lay eggs on the leaves that hatch and appear like brown spots.

These insects get nutrients by feeding on plant fluids and do not harm the plant directly. However, the bacteria they carry can be very harmful.

Insecticidal oils or soaps can help eliminate them. The insect must come in direct contact with the insecticide for it to be efficient. You can repeat this for several days until they’ve completely disappeared.

dying-leaves-flower6. Downy Mildew And Rust

A type of fungus again causes downy mildew. The disease usually appears on the underside of the sunflower leaves and may spread to other parts such as buds and stems.

The fungal growth manifests as spots that appear from gray to purplish to light brown. In some instances, dark brown spots may also develop.

Rust is a fairly common fungal disease among sunflower plants and causes the leaves to develop brown, orange, reddish, purple, or yellow spots on the underside.

Broad range fungicides work pretty well against both diseases.

How To Prevent Sunflower Leaves From Turning Brown?

The trick to ensuring your sunflower leaves never turn brown is following all the best planting practices from the onset. Here are some tips to help you get the planting right:

1. Use High-quality Soil For Planting

Sunflowers thrive best in nutrient-rich soil. The taproot of a sunflower plant can grow fairly deep and reach several feet into the ground.

Ideally, the soil should be loose enough to allow the roots to grow deeply but not too loose that strong wind and excess water can weaken the foundation.

2. Plant Properly

Give adequate spacing between the sunflower seeds to allow the plants to grow well. If the sunflowers grow too close to each other, it will block the flow of air and light.

For bouquet-sized sunflowers, plant them with at least 6 inches of space in between.

Larger-sized sunflowers should be spaced at least 12 inches apart. The hole for each seed should also be about 2-3 inches deep.

3. Choose Areas With Access To Adequate Sunlight

sun-facing-flowerSunflowers love sunlight, but too much exposure can cause the leaves to wilt.

On the other hand, exposure to too little sunlight will affect the bloom. Choose a location with access to the right amount of sun.

4. Try Not To Overwater The Sunflower

Some of the primary causes of browning in sunflower plants are disease-carrying microorganisms. Some of these microbes thrive in extremely humid areas, especially fungi and their spores.

Overwatering your plants creates a humid environment for them to grow.

5. Apply Fungicides And Pesticides Liberally

Fungicides and pesticides are a must while planting sunflowers. They help eliminate harmful disease-carrying pests and microorganisms.

Use organic variants and apply them liberally.

How Often Should You Water Your Sunflower?

Sunflower seeds require generous amounts of water for germination since they contain a lot of natural oil. You should water your sunflower frequently until it begins to germinate.

When growth starts, keep the watering light. Ideally, you should water young plants daily at 3-4 inches away from the stem.

Later on, you can switch to watering your plant once every week as they have developed a high tolerance for heat.

Water the top 6 inches of the soil and make sure you don’t overdo it to avoid complications.

You can use your finger to test the soil to see if it needs water or not. This also helps you determine how much water your plant really needs.

watering-canHow Much Sunlight Does Your Sunflower Need?

Sunflowers are called that for a reason. They love sunlight which is essential for their growth. One interesting fact about young sunflowers is that they’re heliolithic— they move from east to west as the sun rises and begins to set.

As the plant gets older and its stems become stronger, the blooms face only the east and don’t move along the sun all day.

However, overplanting may starve them of enough sunlight.

Lack of sunlight first hastens the growth of young sunflower plants, which you might confuse for a good sign initially. After a while, you’ll notice that the stems of the plants are weak because they are trying to reach for more sunlight.

Note that although sunflowers do thrive in sunlight, they do not always need it for the whole day. At most, 6-7 hours of daylight will be enough to have your plant feeling good and happy.

Another thing to keep in mind is that sunflowers need direct sunlight, especially when growing. However, it’s okay to shelter mature plants; make sure enough sunlight reaches them.

Image Source: Unsplash

How To Care For Sunflowers

I.    Trim the flowers if they’re growing too close together.
II.   Water regularly and more often during the dry season but don’t keep the soil soaked.
III. Be on the lookout for pests and treat them accordingly.
IV.  Grow your plant where the soil is fertile, and there’s enough sunlight. You can apply a well-balanced fertilizer to the soil that’s not fertile enough.
V.    Sunflowers can grow up to three feet (in Germany, there’s a record of a sunflower growing up to nine feet), so it is important to stake them for support as they grow and protect them against heavy wind.


Sunflowers radiate positivity and are very easy to grow. Even beginners wouldn’t have a hard time growing them.

However, they need to be looked after and continually monitored, especially during early growth stages.

If your sunflower leaves start turning brown, troubleshoot the cause using this handy guide.

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