The 7 Most Common Hydrangea Diseases

Hydrangeas are stunning plants that make an impact in any garden, flowering reliably for years and years to come. 

While they are very resilient plants, sometimes they fall victim to disease, in which case you need to act quickly.

Here’s what to look for in hydrangea diseases, and how you can help your hydrangea recover, if you catch problems early enough.

Let’s take a look.

The Signs Of An Unhealthy Hydrangea

Hydrangeas are easy to look after, and most diseases can be avoided by giving your plants the right type of care to begin with, but sometimes it’s just bad luck. 

The first sign of a hydrangea not doing well is when the leaves don’t look right. You might see splotches on the leaves, which may be black, brown, yellow, white, or purple.

The foliage may also start to curl in on itself, wilt, or die back entirely. 

If left for long enough, the disease will spread, and defoliate the entire plant, so it has no more leaves.

Diseases can also affect the way a hydrangea flowers. The flowers may be misshapen, where they don’t open out properly, they can drop from the plant before they should, or they might turn out much smaller than they should.

Some diseases can even spread to neighboring plants, so the quicker you deal with them, the healthier your whole garden will be.

Diseases To Watch Out For

There are quite a few common diseases to be aware of, and methods of dealing with them can vary depending on what disease your hydrangea suffers from. Let’s take a look.

Fungal Diseases

The most common hydrangea diseases tend to be caused by fungal problems, and these tend to spread easily from plant to plant, so the sooner you treat your hydrangea, the better.

Botrytis Blight

Botrytis blight forms on the plant when Botrytis cinerea, a troublesome fungus, takes hold of the plant.

The most visible sign of this fungal infection is when your hydrangea is flowering. Instead of blooming normally, some flower buds won’t open at all, and if they do, the petals will turn brown and will fall off. 

You may also see spots appearing on the foliage, too.

Luckily, this is easily prevented by making sure that there is plenty of airflow around your hydrangea, as well as neighboring plants.

Water your hydrangea in the morning, and only at the base of the plant, and this will stop excess water from becoming a problem.

Fungal Leaf Spot

Caused by bacteria that enters the hydrangea through an injury or open part of the plant, this disease is visible as splotches on the leaves.

There’s no chemical option to treat it, so make sure you keep the area around your hydrangeas tidy, and clean your tools.


More likely to affect Hydrangea arborescens than other species, rust can be a problem. You’ll see golden orange spots on the leaves, and on the undersides, brown splotches.

To prevent it, keep your garden clippers clean, avoid overwatering or watering anywhere but the base of the plant, and keep plant debris off the surface of the soil.

Diluted aspirin in a spray bottle will help treat affected parts of the plant.

Powdery Mildew

It’s much easier to prevent powdery mildew than it is to treat it. It’s easy to spot, leaving a powdery residue on the leaves and stems, which spreads to other plants.

Give your hydrangea enough sunlight and spacing to avoid too much water and not enough airflow around the plant.

If there’s not enough space, trim back your hydrangea and nearby plants to give them some breathing room. 

Treat powdery mildew by using a fungicide or neem oil as a last resort.

Viral Diseases

Hydrangea Mosaic Virus

As you might imagine from the name, you can see this viral disease pretty readily. If the leaves form patterns of yellow mosaics, there’s a good chance that your poor hydrangea is suffering from hydrangea mosaic virus.

New growth will be much smaller, and leaves can have a wrinkled texture. 

There’s no chemical treatment for this virus, so the best way to prevent it is to make sure you don’t leave any plant debris lying around, your tools are clean, and remove pests as soon as you see them.

If you do find this virus on your hydrangea, you should remove it from your garden, making sure that no debris touches the soil. 

Dispose of it responsibly, and do not compost it or put it into a green waste bin. Otherwise, the virus will take root in the compost, and you will have another problem to deal with.

Bacterial Diseases

Bacterial Wilt

There aren’t many bacterial diseases to watch out for when it comes to hydrangeas, but bacterial wilt is one of them.

It’s caused by a bacterium called Ralstonia solanacearum, which takes hold when temperatures have been high for a while, combined with a lot of rainfall.

You will see signs of bacterial rot in blight taking hold of the foliage and the flowers, which eventually gets worse and causes wilt in the top growth, and rot in the roots.

It’s worth noting that you can’t control this disease with chemicals, so you need to make sure that you limit excess moisture, by keeping good air circulation around the plant, and only watering at the bottom.

Make sure you keep the base of the plant clear of plant materials, such as fallen leaves, and random plant debris, and this will help keep bacterial wilt away.

Final Thoughts

Hydrangeas are resilient plants, but if there is something off about the growing conditions, you might see signs of disease. 

It’s much easier to prevent disease in these beautiful plants than it is to cure it, so always keep some room between a hydrangea and its neighboring plants, only water at the plant’s base, and keep your tools clean.

Make sure you dispose of any diseased plant parts responsibly, avoiding putting them into compost or green waste bins.

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