Although there are all kinds of culprits that can cause common problems with hydrangea leaves, more often than not, issues with the foliage are directly related to fungal diseases.
When it comes to growing hydrangeas successfully, there are a few diseases to watch out for, but keep in mind that something as simple as underwatering or a pest infestation can cause your leaves to wilt and drop from the plant.
Here are some issues to keep an eye out for when your hydrangea leaves turn purple, black, brown, white, red and yellow.
Why Are the Leaves Dying on My Hydrangea?
There are a few reasons why the foliage on your shrub might die.
Although hydrangeas aren’t necessarily finicky plants, they do occasionally run into problems.
If you’ve just planted your shrub in the garden or transplanted it into a new container, relax – your plant might just be suffering from a bit of transplant shock. Keep it well watered and monitor the leaves for a few weeks. Give it time to bounce back and protect it as best as you can from the harsh elements (like excessive sunlight or wind).
However, know that browning, burned foliage can also be symptoms of excess fertilizer. Hydrangeas aren’t heavy feeders, so using too much fertilizer for applying it too often can also lead to problems.
Some pests and diseases can also cause your hydrangeas’ leaves to wither, decay, or become discolored. It’s important to keep a lookout for common problems so that you can address them as soon as they are detected.
Here are some of the most common issues you may encounter with the leaves of your hydrangea shrub.
1. Brown Spots on Hydrangea Leaves
If you notice spots on the foliage of your shrub, pay close attention to their patterns and colors.
Brown spots (can also be purple, dark, black or red spots) are usually indicative of a bacterial or fungal infection. The bacteria or fungus doesn’t usually kill the plant, but it can weaken it over time. Of course, they also aren’t the most attractive. You might notice them appearing at cooler periods, like at the beginning of fall.
There are several kinds of fungal diseases that can infect hydrangeas, including anthracnose and Cercospora leaf spot. Cercospora is perhaps the most common and causes purple or brown spots to appear at the base of the plant. These spots are small, occasionally exhibiting brown or purple halos.
It can also cause the leaves to turn fully yellow and then fall off the plant. Anthracnose can also cause pale brown spots to appear – the main difference between this disease and Cercospora is that anthracnose also causes spots on flowers.
You can address both with a fungicide, but it’s far easier to prevent fungal diseases by ensuring proper spacing and air circulation (which can be accomplished by pruning hydrangea plants and limiting your overhead watering).
Bacterial leaf spots can be harder to pinpoint. These usually start at the base of the plant, on the lower foliage, and can be purple, brown, or even red in color. You can use a bactericide but often, fertilizing hydrangea is a good way to help your plant bounce back. A dose of compost tea can be helpful, as can pruning to get rid of the dead and dying leaves.
2. Yellowing Leaves
If the foliage of your hydrangea is turning yellow, it is usually indicative of a problem with the roots – especially if the leaves then fall off the plant.
If your plant was allowed to become too dry, too wet, or was overfertilized, it’s likely that the roots will be damaged. When the roots are damaged, the leaves will wilt, turn yellow, and fall from the plant.
Adjust your watering technique (depending on whether you over-or under-watered) and if you can, repot the hydrangea into a container with fresh soil and better drainage.
3. Brown Edges
As we mentioned earlier, hydrangeas are particularly vulnerable to excess nutrients. Therefore, if you notice both yellowing leaves and browning edges, that’s a good indication that you burned the plant with too much fertilizer.
Flush the soil with water, regardless of whether it’s growing in the ground or a container. This will remove fertilizer salts. Keep flushing until the plant appears healthy and hold off on additional fertilizing for a few weeks.
Rust is a disease that presents much differently than many of these other common problems with hydrangea foliage. It spreads when water splashes on leaves and causes orange spots on the bellies of leaves. Eventually, these leaves can turn brown or yellow and fall off the plant.
You can remove the infected leaves, but addressing your watering technique is essential to prevent it in the future. If the infection is severe, you can use a fungicide specifically for rust.
5. Powdery Mildew
Powdery mildew is easy to identify because it looks just like a grey, powdering coating on the foliage. Another fungal disease, it can be prevented by proper air circulation and watering techniques. Water in the morning and use a fungicide or an organic treatment like neem.
6. Drooping Leaves
Last but not least, if you notice your hydrangea dropping leaves and it’s not the end of the growing season (and none of these other symptoms are present), that’s a good indication that your plant needs to be watered. That’s an easy fix!
How Do You Treat Leaf Diseases on Hydrangeas?
Now that you know about the most common problems with hydrangea leaves, all that’s left to do is to diagnose your specific issue – and treat it! The good news is that most hydrangea diseases can be addressed by improving air circulation and adjusting your watering and fertilizing techniques.
Hydrangeas are tough, hardy plants – so in most cases, using a chemical treatment like a fungicide won’t be necessary!