Troubleshooting
Royal Azalea problems — and how to fix them
Royal Azalea (Rhododendron schlippenbachii) is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Bud blast (Pycnostysanus azaleae)
Buds turn brown and dry without opening, often with grey fungal bristles. Caused by the leafhopper-vectored fungus. Control leafhoppers and remove affected buds promptly.
Vine weevil
Adult notching on leaf margins; larvae destroy roots. Apply a pathogenic nematode drench (Steinernema) in late summer to control larvae in the soil.
Powdery mildew
White coating on young leaves in dry conditions with poor air circulation. Apply a sulphur-based or systemic fungicide and improve air flow around the plant.
Chlorosis
Yellow leaves from iron/manganese deficiency in over-alkaline soil. Apply chelated iron, acidify the soil, and switch to rainwater irrigation.
Frost damage to buds
Late spring frosts blacken open flowers. Shelter with fleece during forecast frosts; site the plant where it will not catch early-morning sun, which accelerates thawing damage.
Prevent royal azalea problems before they start
Most royal azalea issues are care-mismatch, not bad luck. Dial in the basics:
Royal Azalea problems — FAQ
Why is my royal azalea bud blast (pycnostysanus azaleae)?
Buds turn brown and dry without opening, often with grey fungal bristles. Caused by the leafhopper-vectored fungus. Control leafhoppers and remove affected buds promptly.
Why is my royal azalea vine weevil?
Adult notching on leaf margins; larvae destroy roots. Apply a pathogenic nematode drench (Steinernema) in late summer to control larvae in the soil.
Why is my royal azalea powdery mildew?
White coating on young leaves in dry conditions with poor air circulation. Apply a sulphur-based or systemic fungicide and improve air flow around the plant.
Why is my royal azalea chlorosis?
Yellow leaves from iron/manganese deficiency in over-alkaline soil. Apply chelated iron, acidify the soil, and switch to rainwater irrigation.
Why is my royal azalea frost damage to buds?
Late spring frosts blacken open flowers. Shelter with fleece during forecast frosts; site the plant where it will not catch early-morning sun, which accelerates thawing damage.