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The azalea leaves may be drooping due to disease or environmental conditions. The most common reasons are lack of water, especially in pot grown azalea, which need watering regularly. Be careful not to overwater, as this can also cause the leaves to droop and is usually an issue in poor draining soils.
Evergreen varieties can also get drooping leaves caused by frost and cold weather, especially if it’s been mild for a while and then you suddenly get a sharp frost. This can also damage the leaves and cause leaf scorch.
There are some other causes that I cover below plus what to do about them.
Botryosphaeria canker which causes brown stems and drooping leaves
The most common cause of dropping leaves on azaleas is Botryosphaeria canker. This is a fungal disease that affects branches here and there on an otherwise healthy plant. The leaves on the affected stems droop and roll inward and then they turn brown. They don’t fall off but remain lying flat alongside the stem.
What to do
Look for the diseased wood which turns a red-brown colour. Then prune out the dead branches. Make sure to cut the dead branches at least 15cm below the diseased part. Sterilise your cutting tool in-between cuts to avoid spreading the disease. If you notice the disease later in its life cycle, you may need to prune the plant severely.
Phytophthora root rot
Root rot is a serious disease that starts with the leaves dropping and can eventually lead to the azalea’s death. The leaves wilt and droop after they turn yellow. But then the stems also dieback and the whole plant is effected, leading to its demise. Root rot flourishes in the root when the soil is heavy and water-logged.
What to do
Use ericaceous compost and/or grit to make the soil lighter and finer grained, this is best done before planting to prevent rot root in the first place. This helps it to drain properly. Cut away the rotted roots in an attempt to save the rest. If most of the roots are affected by the rot, you need to pull up the plant and destroy it. The fungus may be embedded in the soil and so you may not be able to grow azaleas or any other susceptible plant such as rhododendrons there again.
Chlorosis causing yellowing leaves
If your azalea leaves are drooping and they’re yellow with green veins, your plant has chlorosis. This is one problem you can easily solve. It’s caused by having too alkaline a soil, as azaleas like to be in an acidic environment. Test the pH of your soil with a soil testing kit.
What to do
If you’re using tap water to water your azalea, stop right now. Tap water in a hard water area contains quite a bit of chlorine which causes the soil to become alkaline which prohibits the uptake of iron. Your plant has an iron deficiency. Use rainwater to water your plant. It’s also good practice to collect rainwater into water barrels.
Create a more acidic soil if needed by adding ericaceous (acidic) compost. You need to do this regularly as the soil reverts back to its original alkaline composition.