Why Does My Hydrangea Have Brown Spots

If you’re asking “why does my hydrangea have brown spots,” you’re not alone. This is a very common issue that frustrates many gardeners. Those unsightly marks on the leaves or flowers can be alarming, but they are usually a sign of a fixable problem. Let’s look at the main culprits and, more importantly, what you can do about it.

Most brown spots are caused by environmental stress, fungal diseases, or pesky insects. The good news is that with a little detective work, you can often diagnose and treat the problem yourself. The key is to look closely at the pattern, location, and timing of the spots.

This heading covers the big picture. The specific causes usually fall into a few clear categories. Understanding these will help you narrow down the issue on your own plant.

1. Fungal Diseases: The Usual Suspects

Fungi love warm, wet, and humid conditions. If your hydrangea leaves are getting splashed a lot or the air around them is still, fungal spores can take hold. Here are the most common fungal diseases that cause brown spots.

Cercospora Leaf Spot

This is probably the most frequent cause of brown spots. It starts as small, circular purple or brown spots on the lower leaves. As it progresses, the spots enlarge and develop a tan or gray center with a purplish border. Severely infected leaves will turn yellow and fall off.

Anthracnose

This fungus causes larger, more irregular spots. They can be brown, tan, or even black and often have concentric rings inside them, like a bullseye. Unlike Cercospora, Anthracnose can also cause large, sunken lesions on the stems and flower petals.

Powdery Mildew

While it starts as white powder on leaves, a bad case can lead to leaves turning brown and crispy. You’ll usually see the white residue first, especially on the undersides of leaves.

2. Environmental Stress: Water and Sun Issues

Sometimes, the problem isn’t a disease at all. Your hydrangea might be telling you it’s unhappy with its care.

Leaf Scorch: This happens when leaves lose water faster than the roots can absorb it. It often occurs in hot, windy, or sunny conditions, especially if the plant is underwatered. Brown, crispy patches appear on the edges and between the veins of leaves, particularly those facing the sun.
Overhead Watering in Sun: Watering your hydrangea from above on a sunny day can act like a magnifying glass. Water droplets on the leaves can focus the sun’s rays and cause small, scorched brown spots.
Fertilizer Burn: Applying too much fertilizer, or applying it to dry soil, can “burn” the roots. This damage shows up as brown, crispy leaf margins and spots.

3. Pest Problems: Insects Causing Damage

Certain insects can create damage that looks like brown spots. You’ll need to inspect the undersides of leaves closely.

Spider Mites: These tiny pests suck sap from leaves, causing stippling (tiny yellow dots) that can merge into larger brown, dry patches. You might see fine webbing.
Scale Insects: These look like small, brown, bumpy spots stuck to stems and leaf veins. They weaken the plant, which can lead to browning leaves around the infestation.

How to Diagnose Your Hydrangea’s Brown Spots

Follow these steps to figure out what’s going on.

Look at the Pattern: Are spots circular or irregular? Small and numerous or large and blotchy? Do they have a colored border or rings?
Check the Location: Are spots only on older, lower leaves? Are they on new growth too? Are they on the flower petals as well?
Consider the Weather: Has it been very hot, dry, and sunny? Or has it been exceptionally rainy, humid, and cloudy?
Review Your Care: How have you been watering? Did you recently fertilize? Is the plant in full, blazing sun all day?
Inspect for Pests: Turn leaves over. Look for tiny moving dots (mites) or unusual bumps (scale). Use a magnifying glass if you have one.

Treatment and Solutions: How to Fix Brown Spots

Once you have a likely diagnosis, you can take action. Always start with the least invasive method.

For Fungal Diseases:

Remove Affected Leaves: Prune off the worst-spotted leaves and any that have fallen. Put them in the trash, not the compost, to prevent spores from spreading.
Improve Air Flow: Thin out the center of the plant or nearby plants so air can circulate better. This helps leaves dry faster.
Water at the Base: Water the soil directly, not the leaves. Soaker hoses or drip irrigation are ideal. Water in the morning so any splashed leaves dry quickly.
Apply Fungicide: For severe cases, use a fungicide. Neem oil or a copper-based fungicide are good organic options. For Cercospora, chlorothalonil is effective. Always follow the label instructions carefully.

For Environmental Stress:

Adjust Watering: Hydrangeas need consistent moisture. Water deeply when the top inch of soil is dry. Mulch with 2-3 inches of bark or compost to help retain soil moisture and keep roots cool.
Provide Afternoon Shade: If your hydrangea is in full, hot sun (especially in hotter climates), consider transplanting it to a spot with morning sun and afternoon shade, or use a shade cloth.
Flush Fertilizer Burn: If you suspect over-fertilizing, water the plant deeply several times to help leach excess salts from the soil.

For Pest Problems:

Spider Mites: Spray the plant forcefully with a strong jet of water from your hose to dislodge mites. Repeat every few days. Insecticidal soap or neem oil are effective follow-up treatments.
Scale: Scrape off small infestations with a fingernail. For larger problems, apply horticultural oil in the dormant season or use insecticidal soap during the growing season.

Prevention is the Best Medicine

Keeping your hydrangea healthy from the start is easier than treating problems. Here’s how to prevent brown spots.

Choose the Right Location: Most hydrangeas prefer morning sun and afternoon shade. Check the requirements for your specific type.
Plant Properly: Don’t crowd your hydrangea. Give it enough space for good air circulation as it matures.
Water Wisely: Deep, infrequent watering at the soil level is key. A layer of mulch is a hydrangea’s best friend.
Clean Up in Fall: Always clear away fallen leaves and debris from around the base of the plant to remove overwintering fungal spores.
Disinfect Tools: Wipe your pruning shears with rubbing alcohol between cuts, especially when removing diseased wood.

FAQ: Quick Answers About Hydrangea Brown Spots

Q: Should I cut off brown leaves on my hydrangea?
A: Yes, you can prune leaves with severe spotting. This improves looks and helps prevent disease from spreading. Just don’t remove more than a third of the plant’s foliage at once.

Q: Can overwatering cause brown spots?
A: Yes, indirectly. Constantly soggy soil stresses roots and creates a humid environment perfect for fungal diseases, which then cause the brown spots.

Q: Why are there brown spots on my hydrangea flowers?
A: This is often botrytis blight, a fungal disease that thrives in cool, wet conditions. It can also be from physical damage like heavy rain or overhead watering. Remove affected blooms and improve air flow.

Q: Is it too late to save my hydrangea if it has brown spots?
A> No, it’s rarely too late. Hydrangeas are resilient. Even if it loses all its leaves, it may regrow from the roots if the crown is healthy. Focus on correcting the cause and providing good care.

Q: What is a good homemade spray for fungal spots?
A: A baking soda spray can help as a mild fungicide. Mix 1 tablespoon of baking soda and 1/2 teaspoon of liquid soap (not detergent) in a gallon of water. Spray thoroughly, including leaf undersides. Test on a small area first, as it can sometimes cause phytotoxicity.

Seeing brown spots on your hydrangea can be worrying, but now you have the knowledge to tackle it. Start by playing detective—examine the spots, think about your weather and care routine. Most often, the solution involves simple changes: watering at the roots, improving air flow, or providing a bit of shade. With the right adjustments, your hydrangea can bounce back and produce those beautiful, healthy blooms you’re hoping for all season long.