azalea leaves - Ask Extension
I planted an azalea bush last season. It was doing well until a month ago or so. There's a brown color on most leaves--not just the ends. They look li...
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azalea leaves #760982
Asked July 10, 2021, 12:53 PM EDT
I planted an azalea bush last season. It was doing well until a month ago or so. There's a brown color on most leaves--not just the ends. They look like a lot of tiny brown dots. A master gardener looked at them and thought rust but then looked closely and said she didn't think it was rust but didn't know what it was. I've been spraying with soapy water for the last several days with no apparent results yet.
Hennepin County Minnesota
Expert Response
It looks like rust to me. Rust can be a problem on azaleas. Read here:
https://extension.umd.edu/resource/rust-disease-shrubs
Perhaps a larger problem that I see in the photos is that the leaves appear chlorotic. Chlorosis is a symptom of too little iron, which, in turn, is caused by soil pH being too high. Azaleas must have very acid soil (pH of 5.5 or below):
https://hortnews.extension.iastate.edu/1994/4-6-1994/ph.html
In Minnesota, using fertilizers for acid-loving plants is usually not sufficient. If you have not amended your soil to address soil pH, you may have a problem that will be increasingly difficult to deal with. Start by getting a reliable soil test done:
https://soiltest.cfans.umn.edu/testing-services/lawn-garden
https://extension.umd.edu/resource/rust-disease-shrubs
Perhaps a larger problem that I see in the photos is that the leaves appear chlorotic. Chlorosis is a symptom of too little iron, which, in turn, is caused by soil pH being too high. Azaleas must have very acid soil (pH of 5.5 or below):
https://hortnews.extension.iastate.edu/1994/4-6-1994/ph.html
In Minnesota, using fertilizers for acid-loving plants is usually not sufficient. If you have not amended your soil to address soil pH, you may have a problem that will be increasingly difficult to deal with. Start by getting a reliable soil test done:
https://soiltest.cfans.umn.edu/testing-services/lawn-garden
