Answer: Based on your description I can't tell you exactly what is wrong with your plants but I can make some suggestions. Azaleas prefer an acid soil and sometimes lime leaching from concrete will affect nearby soil pH. nt principle it is a good idea to have your soil checked including pH since the plants aren't growing well, but the specific symptoms don't match what you have described. The white could be a sign of fungus such as mildew or it could be a sign of insect infestation such as lacebug. Either one of these could cause stunting and overall lack of vigor. You might want to take a sample to your County Extension (489-4315) for a specific diagnosis and control suggestions; they can also help you with the soil test and interpreting the results. In the meantime, clean up, remove and destroy any fallen foliage to minimize reinfection.
Azaleas need a humusy soil with plenty of organic matter worked in. It should be evenly moist yet very well drained and never soggy. These plants are shallow rooted so need careful watering; a few inches of organic mulch such as shredded bark will help keep the soil moist and cool. It will also help feed the soil as it breaks down.
Finally, they are not heavy feeders and don't usually grow very fast to begin with. Some types are dwarfs and grow only an inch or two a year even under the best of conditions. To some extent the growth rate you should expect will depend on the variety of azalea you have as well as their care and growing conditions.
Good lcuk with your azaleas!
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