Answer: When an azalea fails to leaf out or bloom, it indicates there is a problem of some kind. Since the others seem to be fine, it may be due to a slight difference in location such as more exposure to wind (so it experienced a harsher winter), more or less soil moisture due to the drainage pattern, or something like that. Or, it could be due to the plant not being as well rooted as the others.
Azaleas as a group are slow growing by nature. They will need a year or two to become well established and rooted, and then should begin growing although it may be only a few inches a year.
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