Why Are My Sunflower Leaves Turning Yellow? Should They?

Sunflowers are the suns of the gardeners’ world. It’s undeniable; it’s right there in its very own name. There’s nothing quite like seeing rows upon rows of this beautiful bloom. Even single planted sunflowers can pack a stunning punch for garden visuals. However, it can be frustrating when your sunflowers aren’t quite as healthy as you would like them to be, and their leaves turn an unsightly yellow color.

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But why are my sunflower leaves turning yellow? Over-watering, the age of your plant, and even nutrient deficiencies are all causes of yellow leaves. However, it could also indicate your sunflower is suffering from a fungal infection or insect infestation. Thankfully, there may be ways to rectify these issues before your sunflower goes beyond the point of no return.

Keep reading to find out why your sunflowers’ leaves are turning yellow and what you can do to help bring them back to life.

Why Does My Sunflower Have Yellow Leaves?

There are many reasons such as fungal root rot, nutrient deficiencies, mites, being root bound, or just the plant coming towards the end of its blooming season that can cause your sunflowers’ leaves to go yellow.

Growing sunflowers can be such a gratifying experience. 

Mainly thanks to their short yet super speedy growing season, which means you won’t have to wait too long to see that beautiful sunflower head bloom.

But it can be so disheartening when your sunflowers’ leaves start turning yellow. 

Let’s be honest; it’s just not that pretty.

So here are some reasons that your sunflowers’ leaves could be turning yellow.

Fungal Root Rot

One of the most common reasons for your sunflowers’ leaves to be turning yellow is fungal root rot. One thing about sunflowers is that their root systems, although vast and strong, can be very susceptible to damage. 

Fungal root rot usually occurs when your sunflowers’ surrounding soil is overly moist or waterlogged for a longer time. 

This is a common issue for heavy clay soils that have poor water drainage or if you have been overzealous when it comes to watering your plant.

Although sunflowers do need a healthy amount of water during their early stages of growth, once they have matured, their water needs decrease dramatically.

Luckily for us, the yellowing of your sunflowers’ leaves is one of the very early indicators of fungal root rot. 

Meaning, saving your plant will be much easier than if you let the fungal infection grow.

Nutrient Deficiencies 

Common nutrient deficiencies that your sunflower may experience are nitrogen and phosphorus deficiencies. 

Both of these can be a big problem, but it is the nitrogen deficiency that will result in yellowing leaves on your sunflower plant. 

  • Phosphorus deficiency will result in your sunflowers leaves developing purple or red discoloration

It’s highly unlikely that your sunflower will need any extra nutrient boosts in the earlier part of its growth cycle but, as it matures, you may need to give it a top-up to keep it healthy and beautiful.

Root Bound

If you are growing your sunflowers directly into the soil, this won’t be an issue, but for those of us who grow our sunflowers in containers or pots, there is a risk that your sunflowers will become root-bound.

Sunflowers have very large root systems and can very quickly run out of room in their containers. Not only can this result in the yellowing of your sunflowers’ leaves, but it can also reduce this plant’s stability.

Downy Mildew

Downy mildew is another fungal infection that thrives in wet and soggy soil and humid environments.

Seedlings that are overwatered and far too close to each other are at a higher risk for developing downy mildew, resulting in yellowing leaves as a very early indicator of infection.

It is easily spread from one plant to another by airborne spores and, if not caught early enough, will kill your sunflowers.

Spider Mites

Spider mites are the miniature vampires of the garden and are every gardener’s worst nightmare.

They can be very difficult to see without the aid of a magnifying glass, but they do spin very fine webs over infested plants.

So you are more likely to spot their webs before the spider mites themselves.

These vampire-like critters love to feed on plant fluids by piercing the plant tissue, which kills your sunflowers’ foliage and eventually leaves your bloom with no means to photosynthesize. 

Aphid Infestation

Aphids are very small insects, very much like spider mites. They also feed off of a plant’s sap. They feed in clusters on the underside of leaves and can be fairly easily spotted. 

An aphid infestation can lead to your sunflowers’ leaves curling, turning yellow, and slowly dying off.

Coming To The End Of Its Blooming Season

If no other issues seem to be present, your sunflower may just be reaching the end of its natural life cycle. 

When a sunflower reaches the end of its life, leaves may turn yellow before ultimately turning brown, withering, and dying. 

There’s nothing you can do about this issue; it’s just the natural progression of your sunflower.

Are Sunflower Leaves Supposed to Turn Yellow?

No, your sunflowers’ leaves aren’t supposed to turn yellow in most cases. The only exception is when they have reached the end of their life cycle

Being vigilant about what issues your sunflower maybe experience can help you to decide whether the yellowing of their leaves is a correctable problem or just a natural process. 

If your sunflower is still a seedling and you find its leaves aren’t their usual vibrant green, you can already be sure there are other problems at play.

If your sunflower has been blooming for a few weeks, your sunflower may have fully matured and at the end of its life.

How Can You Stop Your Sunflowers Leaves From Turning Yellow?

There are many things you can do to stop your sunflowers’ leaves from turning yellow depending on what problem is causing the issue, such as using fungal sprays, testing soil ph levels regularly, tracking your watering schedule, and much more.

Treating Fungal Rot or Infection

If your sunflower is a fungal root, rot allowing the soil to dry out can help. 

However, if your soil drains poorly, you may need to remove the entire plant from its current home and allow the roots to dry out before replanting in a less soggy place. 

You will also need to use a fungicidal spray to get rid of the fungal root rot infection.

This is the spray to buy off Amazon – look at the reviews!

This is also the same for downy mildew. 

You will need to treat your sunflowers with a fungicide specific to downy mildew eradication. However, you won’t need to remove it from its current spot.

Treating Insects

When it comes to little beasties like spider mites and aphids, both require different treatments. 

Aphids can be easily blasted off of your sunflower with a water hose, but if the aphid colony is persistent, you can use an insecticidal spray.

As for spider mites, they are a little bit more voracious. 

Most insecticidal sprays won’t work on spider mites; if anything, they may lead to a population explosion.

Purchasing a spider mite-specific insecticidal soap or spray with help rid your dramatic blooms of the little vampire feeders.

This is the product you need from Amazon for this specific purpose.

If you find your sunflowers’ leaves are yellowing due to being root bound, this is an easy fix. 

Moving Your Sunflower(s)

Moving your sunflower to a newer and much larger pot of container will give more room for their root systems and allow them to revive all by themselves. 

You just have to be careful to damage your sunflowers’ roots or disturb them too much.

Resolving Nutrient Deficiencies

Nutrient deficiencies can also be a common problem in sunflowers that can be easily fixed by purchasing a nitrogen-based plant feed from any horticultural store and treating your sunflower with the amounts shown on the bottle or container. 

Give your plant a chance to build up its nitrogen reserves before panicking if its leaves don’t immediately turn their healthy, vibrant green color.

How Do You Remove Yellow Leaves From Your Sunflower?

Removing yellowing leaves from your sunflower plant isn’t necessary, but if you want to, a quick snip with garden clippers or even house scissors will do the job nicely with very little damage to the rest of your sunflower. 

One thing we suggest you don’t do when considering removing your sunflowers’ yellowing leaves is to clip them off before you have found a reason behind their discoloration in the first place. 

Depending on the issues affecting your sunflower, many yellow leaves can bounce back fairly quickly and won’t need to be removed at all.

As long as you aren’t removing all your sunflowers, leaves a few snipped here and there won’t cause any long-lasting damage.

Finally

Yellowing leaves on your sunflowers can be concerning, but the majority of the time, it’s no major cause for concern with many easy solutions to help your sunflower thrive throughout its lifetime. 

Be vigilant, as with any garden plant, and you will have beautiful sunflowers all summer long.