Many people’s hydrangea knowledge begins and ends with the fact that you can sometimes change their color by making the soil more or less acidic. But there are lots more that go into growing the biggest and healthiest mopheads possible!
Hydrangeas are most often grown for their flowers but the leaves offer plenty of ornamental interest on their own. Unfortunately, hydrangea leaves tend to be the first part of the plant to show signs of stress and disease.
In this article, I’ll share the most likely causes of hydrangea leaves turning brown and equip you with the best ways to fix the problem at hand.
Why Do Hydrangea Leaves Turn Brown?
Hydrangea shrubs are classified as deciduous perennials. This means that their leaves naturally die off each autumn when temperatures drop and daylight hours shorten. There’s nothing you can do to prevent this and — rest assured — it has no relation to your plant’s health.
Brown leaves are a problem when they appear in the spring or summertime. New hydrangea leaves typically bud out in early spring and should remain green until well into the fall. Brown foliage that appears during this time period usually means that something is wrong with the shrub’s growing environment or general health.
There are several reasons why hydrangea leaves might turn brown during the active growing season. Some of the most common environmental causes include drought, hot weather, and frost damage. Other explanations might include disease, pest infestation, or improper fertilization.
What Causes Brown Hydrangea Leaves
You’re probably reading this because your hydrangea shrub is looking less than its best. Before you can take steps to fix the problem, you need to narrow down the cause of its brown leaves.
Below you’ll find the most likely reasons for a hydrangea’s leaves turning brown and some of the best ways to treat each.
Too Much Heat
Most hydrangeas are adapted to cool, shady areas and do not tolerate heat much or at all. It’s very common to see hydrangea leaves turn yellow with brown edges when exposed to too much direct sunlight during the summertime.
Planting location is a big deal for hydrangeas. They prefer to grow somewhere that is cool and partially shaded during the hottest part of the day. Select a location that receives an average of 6 hours of daily sunlight, preferably during the morning.
If you live in a warmer area — i.e., USDA Zone 5 or further south — I recommend planting oakleaf hydrangeas. These varieties are naturally better suited to hot environments than bigleaf or panicle hydrangeas.
For hydrangeas that are already in the ground, the best thing you can do is ensure the plant gets plenty of moisture during hot weather. Consider installing a layer of mulch to slow down soil evaporation.
Another potential fix is to increase the amount of shade around your hydrangea during the hottest, brightest hours of the day. You can do this by installing a section of privacy fence, setting up a shade net, or even planting large trees or shrubs nearby.
Prolonged Drought
Hydrangeas can tolerate brief periods of drought. You may even notice the canes droop slightly at midday only to perk back up by evening time. However, repeated or persistent wilting can cause extreme stress and visible damage.
If your hydrangea’s brown leaves are the result of dehydration, you’ll likely notice discoloration starting at the tips or margins and an overall dry texture. The leaves may also wilt or curl inward.
Hydrangeas need about 1 inch of water per week to thrive. Established shrubs usually don’t need watering except in extremely hot or dry weather. Note that plants grown in hot climates or excessively sunny areas will naturally need more water than their peers.
Many gardeners encounter the above symptoms of dehydration despite watering their hydrangeas frequently. If this sounds like your situation, I’m willing to bet that you’re not watering long or deep enough for your plant’s needs.
Another common problem is that rain or hose water runs off or drains too quickly. Amending the soil around your hydrangea with additional organic matter is one way to alleviate this problem.
Wet Leaves
Did you know that you should always water hydrangeas at the base of the plant and never over the top of it? In fact, watering your hydrangeas incorrectly could be what’s causing their brown leaves. There are two main reasons why:
- Hydrangea leaves are highly susceptible to fungal diseases that love damp environments.
- Hydrangea leaves can be burnt when sitting water droplets act as ‘magnifying glasses’ for the sun.
In addition to irrigating only at ground level, it’s a good idea to water hydrangeas in the early morning. Watering at the start of the day gives any wet leaves plenty of time to dry before mid-day (when the sun is strongest) or evening (when fungal spores are most active).
Of course, hydrangea leaves can also become wet due to rainfall and dew. Keep an eye on any shrubs planted in the heavy shade as they may take longer to dry off.
Fungal Disease
While damp leaves are a major risk factor for infection, we also need to talk about diseases that affect hydrangeas in general. There are three common fungal diseases that cause brown hydrangea leaves:
Rust
Rust — caused by the fungus Pucciniastrum hydrangeae — is a foliar disease common in smooth hydrangea varieties. The most obvious symptom is orange, yellow, or brown spots that first develop on the undersides of leaves. As the disease worsens, spots will also form on the tops.
The best control strategy is to monitor hydrangeas for early signs of infection and remove and destroy affected limbs. Invest in proper watering techniques and ensure good air circulation both in and around shrubs. Routinely clean up old plant material and sanitize tools so that the fungal spores have fewer places to spread.
Anthracnose
Anthracnose is a widespread woody plant disease caused by several species of Colletotrichum fungi. It typically spreads in wet growing conditions and can infect a large number of popular landscape shrubs.
A hydrangea infected with this disease will present with brown spots across both the leaves and flower petals. The spots can be almost any size and may be round or irregularly shaped.
Recommended control strategies are similar to the ones I mentioned above for controlling rust. Also, note that anthracnose is easily spread from the soil in splashing water droplets, so avoid using high-powered sprays when irrigating your hydrangeas.
Leaf Spot Disease
Leaf spot disease is caused by multiple types of fungi. Taking a close look at your hydrangea’s leaves will probably help you identify the exact culprit but treatment is generally the same for all.
Phyllosticta Leaf Spot (Phyllosticta hydrangeae-quercifoliae) causes circular, water-soaked leaf spots that develop brown borders as they age.
Alternaria Leaf Spot (Alternaria spp.) causes large brown spots with yellow halos to form on the top surface of leaves. These spots commonly appear along the leaf margins.
Cercospora Leaf Spot (Cercospora hydrangea) causes pinhead spots that usually appear on the bottommost leaves first. Infections typically occur late in the growing season.
Preventing the spread of any of these fungal pathogens involves removing and destroying infected plant matter and adhering to sanitary best practices for all gardening tools and supplies. Chemical fungicides may also offer some early protection when used according to manufacturer guidelines.
Transplant Shock
Brown leaves on newly planted hydrangeas are often a sign of transplant shock. Continue providing proper care — including regular deep waterings — and the damage should fade away over time.
Transplant shock is generally caused by moisture loss during the planting process, so try to get your new hydrangea in the ground as quickly as possible. As always, remember that freshly planted shrubs need more water than established ones.
If your hydrangea’s health continues to decline, it may mean that it was planted incorrectly. For example, a planting hole that is too shallow or too narrow for the shrub’s root system will prevent it from establishing itself.
Fertilizer Burn
Fertilizing with the wrong formula or too late in the season can burn plant roots and foliage. Excess nutrients in the soil dry out and damage the roots, which in turn keeps the shrub from taking in adequate moisture.
My own hydrangeas do just fine without routine feeding but your mileage may vary. The general advice is to apply one or two doses of fertilizer in the spring before blooms emerge. Most hydrangeas respond best to a balanced nutrient ratio — e.g., 10-10-10.
Fertilizer burn is more likely in the summertime because the soil is already on the dry side. If your hydrangea does show early signs of over-fertilizing, the best course of action is to flush the surrounding soil with plenty of clean water.
Also, be aware that fertilizer can run off from other parts of your lawn or garden and end up in your hydrangea bed.
Pest Infestation
Common garden pests like aphids and spider mites will feed on hydrangea leaves if given the chance. These shrubs are also extremely attractive to Japanese beetles in the summer months.
Aphids and spider mites feed by sucking the sap out of plant leaves. When they pierce the leaf surface with their mouthpieces, they damage the tissue and leave behind brown spots. Over time, excessive feeding can dry out individual leaves to the point that they turn almost entirely brown.
Japanese beetles feed by taking bites out of interveinal leaf tissue. You might notice ‘skeletons’ of previously healthy leaves where these beetles have been active. Affected foliage often grows more and more brown the worse the pest damage becomes.
You can manage active infestations by spraying with neem oil and insecticidal sprays. Alternatively, you can try brushing or shaking the offending pests off. Some gardeners also recommend blasting them off with a strong jet of water, however, this can potentially lead to other issues such as fungal infections if leaves are wet for prolonged periods.
Frost Damage
Hydrangeas start putting out new growth very early in the year, which leaves them vulnerable to late spring frosts. This is particularly the case with bigleaf varieties because they exit dormancy very easily.
The biggest risk of frost damage is its effect on emerging flower buds. I recommend insulating hydrangeas during periods of cold spring weather to help protect and preserve the new year’s buds.
The good news is that established hydrangeas generally have no issue recovering from frost damage. You might notice the existing foliage turn brown and die off but new, healthy leaves should follow close behind once the frost has passed.
For information about what to plant alongside your Hydrangeas, click this link.
FAQ Hydrangea Leaves Turning Brown
What Does an Overwatered Hydrangea Look Like?
It’s sometimes hard to differentiate between an overwatered and an underwatered hydrangea. Both issues cause symptoms like drooping or wilting leaves. In cases of overwatering, these symptoms are often accompanied by yellowing that starts with the lower foliage. Underwatered leaves are more likely to turn brown and dry.
Citations
- Tennessee State University Fungal Diseases of Hydrangea
Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.
