Last Updated on March 4, 2022 by Grow with Bovees
If you’ve noticed that your azalea leaves are turning brown, or reddish brown and falling off, then you know that you may have a problem.
There are also some issues that cause discoloration of azalea leaves that makes them turn white, black, yellow, and develop brown spots.
The change of leaf color in azaleas is sometimes an indication of a serious issue, sometimes it’s nothing to worry about.
To find out how to identify and fix any potential concern with your azaleas, follow our azalea leaf discoloration guide below.
Why Your Azaleas Are Discolored
There are several reasons as to why your azaleas lush green foliage is starting to change color, making it an unsightly plant to look at.
The reasons for leaf discoloration may be due to a pest or disease issue, you may have soil issues such as nutrient deficiency, sandy soil or too wet soil conditions.
The change of color in leaves may also arise due to external factors such as dehydration, poor drainage, leaf burn from the sun or injury due to the cold.
Another reason for the azaleas shiny green leaves to suffer from discoloration that should be considered, is natural seasonal changes. Which brings me to my next point.
Natural Seasonal Discoloration
Autumn is the season during which most plants start to either display a different color on their leaves or even shed leaves.
So, discoloration of the leaves during this time is normal, and it should rectify itself as soon as the season changes.
In fall, your azalea may show off beautiful shades of red, orange, yellow and sometimes even purple on its leaves. Some leaves will also start to turn brown.
Keep in mind that deciduous azaleas even shed their leaves before winter and an evergreen variety can also drop a few leaves during this season.
If your azalea starts acting up like this during another season of the year — summer, for example — this is when alarm bells should ring, and you should investigate further. Your plant may be under severe stress due to another source.
Why Do Azalea Leaves Turn Brown?
Azaleas are generally healthy plants, but there are quite a few reasons for the browning foliage of azaleas. In fact, anything that is able to kill azaleas may cause leaf browning.
There are other signs that one can look out for in order to figure out exactly what is the cause of your azaleas turning brown.
Continue on for a few different causes of brown leaves.
Dieback Disease
If your azalea has a dieback fungus, you will notice browning leaves on a few branches. This issue is caused by pests and fungi.
Phytophthora and botryosphaeria are two fungi that may cause brown leaves on your azalea. If your plant has a fungal growth of phytophthora — which is quite lethal and is also the culprit for root rot — the leaves will start looking pale, then turn to yellow and then brown, after which they will start falling off, followed by the entire branch eventually dying if there is severe leaf damage. It can also cause crown rot.
If the plant is suffering from the botryosphaeria fungus, the leaves will also go brown, and they will start curling. In this case, however, they do not fall off.
Lace bug infestations are also a common cause of dieback. They are often found on the underside of leaves.
The best thing you can do is to prune away the dead branches and infected leaves at the tips of stems. This way, you can prevent it from spreading any further.
Insufficient Water
Wilted and droopy leaves that are crispy and have brown leaf tips and edges, are an indication that you are not watering the shrub enough. To fix this problem, simply provide it with more water and observe whether the problem improves or subsides.
Winter Injury
Most azalea varieties are not winter hardy plants, and they are not very fond of being exposed to a lot of wind or too cold weather. During winter, the plant may be unable to absorb enough water through the frozen ground, turning the entire leaves brown and drying them out.
Winter injury affects the plant in such a way that it either causes a few random leaves to turn brown or only the tips and edges of a few leaves in between become brown.
It is important to remember that such an injury may only be visible much later, in spring or summer, or months after the damage has been done.
There is, unfortunately, no way to fix it once the damage is done. Your best bet is to let it be and hope that your azalea recovers on its own.
Season Changes
As mentioned further above, fall may cause the leaves of your azalea to turn brown and fall off before winter.
Root Damage
Diseases or problems with azalea roots, is also a common cause of brown leaves on azalea plants.
There are many things that can increase the chances of root rot and disease infected roots. These include poor soil drainage, soggy soil caused by over watering, root rot, fertilizer burn and stunt nematode.
If the entire root ball is already dying, it is near impossible to save. We suggest you try and prevent the healthy roots from also being damaged, by amending poor drainage conditions to control soil moisture, for example.
Why Do Azalea Leaves Get Brown Spots?
Instead of brown leaf discoloration, you may notice that your leaves have developed small brown spots on their surface. These spots can be caused by several things, which include sun damage, fungal leaf spots and leafminer insects.
Leafminers
These rhododendron borers are known as Caloptilia azaleella and like to show up during spring, continuing to spread throughout summer by boring holes in stems and holes in leaves. This common pest causes brown leaf tips which are curled together with some brown dots on various leaves.
These caterpillars enjoy feeding on leaves, and they are, in fact, found living inside small pockets in the leaves near the central vein. These pockets are known as mines, hence the name leafminers.
Fungal Leaf Spot Disease
Uneven polka dot-like brown speckles on leaves are a good indication of a fungal infection. This type of leaf spot infection may eventually cause leaf loss.
Prune away all affected parts of the plant using pruning shears and dispose of them properly. Fungus tends to spread if not destroyed correctly.
A serious fungal infection can be treated by using a fungicide before the plant blooms, be aware that you don’t kill off beneficial insects in the process.
Leaf Burn
Brown dots on the top side of the leaves that resemble splotches rather than perfect little dots, is often a sign that your azalea is getting too much sun. Too much sun can damage leaves.
Damaged leaves due to leaf scorch can’t be fixed. Try to protect your plant from any future damage, by placing it in a spot of less direct sun and more shade, dappled sun or filtered light.
Why Do Azalea Leaves Turn Yellow?
There are several reasons as to why azalea leaves turn yellow, some of which have already been discussed above. These include pest infestations, sun scald, dehydration, seasonal changes and root diseases.
Nutrient Deficiency
Yellow leaves, together with slow growth, can be a sign that the azalea is lacking vital nutrients. This happens, if the soil is not fertile enough, deficient in essential nutrients such as calcium, nitrogen, iron, magnesium and potassium.
Add some all-purpose fertilizer to your soil. Compost and mulch are also a good solution to a lack of soil fertility.
Chlorosis
This is a condition of the leaves where they lack chlorophyll, causing them to go pale and yellow.
This condition is caused by root problems, too dense soil, nutrient deficiencies and other plant diseases.
Not Enough Soil Acidity
Much like other plants, azaleas are also acid loving plants.
Soil pH, which is too alkaline, can cause yellowing of azalea foliage. An alkaline soil prevents the absorption of iron, which is vital for the healthy development of the azalea. They like slightly acid soil ranging between 4.5 and 6 when cultivating azaleas. Most average garden soils range between 6 and 7.
Spray the yellow leaves with some chelated iron or enhance the acidity of soil with aluminum sulfate or soil sulfur, bearing in mind that this is only a temporary fix. For a more permanent solution, relocate the plant into more acidic soil or amend the soil it is growing in, to gain more acid soil conditions.
Why Do Azalea Leaves Turn White?
Bleached-out or gray looking leaves are most commonly caused by pests or powdery mildew. Let us have a closer look at these.
Pests
If your plant is infested with pests that feed on it by sucking the sap from it, they will leave the foliage speckled gray or white. You may even find white speckles on the leaf surface if the infestation is advanced.
The most common piercing-sucking pests that cause this white leaf discoloration are spider mites and azalea lace bugs nymphs. With severe infestations of spider mites, you will find webbing over the leaves. Inspect your plants for pest damage and apply the pesticide of your choice to get rid of them.
Powdery Mildew
Powdery mildew is a fungal spore that spreads across leaves, making them appear white or gray. It starts off with a small spot during summer, but it can spread across the entire top and bottom part of the leaf.
The fungus is likely to spread on wet foliage and too moist conditions. Improve soil drainage and use an all-purpose fungicide to rid your infected plant of mildew.
Why Do Azalea Leaves Turn Black?
Black leaves or black spots on your azalea could be quite shocking, but it does happen. Here is how.
Sooty Mold
Finding a black coating on leaves is an indication of a pest problem. Sooty mold comes from honey dew left on the leaves by bugs. Honey dew is a sticky waste product excreted by several insects.
Whiteflies and bark scale are the biggest culprit for sooty mold forming on the azalea leaf surface.
Although the affected leaves look gross, it is not the end of the world. A whitefly infestation can easily be eradicated by using neem oil or insecticidal soap. The sooty mold can easily be washed off of the leaves surface. Do not forget to inspect the undersides of leaves as well.
How To Keep Azalea Leaves Green
Now that you are aware of what may cause your azalea leaves to discolor, we would say that the best way to keep the leaves green is to keep your plant healthy and prevent these concerns altogether.
Keeping your shrub happy and healthy is not hard to do, as long as you don’t start off on the wrong foot.
For healthy azaleas start off by choosing an azalea variety that can easily adapt to the climate in which you reside. Place it into azalea-friendly soil, with proper soil drainage and make sure it gets the proper amounts of shade and sunlight. Water it appropriately by setting up a fitting watering schedule and mulch it yearly. The perfect soil for azaleas is consistently moist but well-drained soil.
If you notice your azalea leaves turning brown, or any other discoloration, carefully inspect the affected azaleas and their symptoms to come to a diagnosis, after which you can treat the issue accordingly.
If all else fails, and you can’t achieve healthy plants, plant bug-resistant varieties to spare you the stress.
We hope that with this you can keep your azalea leaves beautiful, healthy and green. Good luck!
References:
https://pubmed.ncbi.nlm.nih.gov/30812513/
https://s3.wp.wsu.edu/uploads/sites/687/2015/06/MG-Canker-and-Wilt-Diseases-3.27.15-01.pdf