After the last chance of a frost and before the end of summer. However, fertilizing may not be advisable if the plants are healthy and may actually reduce the amount of bloom.

Plants that have been given a soil mixture rich in organic matter probably will not need feeding for several years. Do not stimulate fast growth because it produces long weak stems and few flowers. But if a plant seems weak or sickly, use cottonseed meal or a special rhododendron-azalea-camellia-holly fertilizer such as Hollytone dusted on the soil in early spring. Supplemental feeding later is not normally needed, but phosphorus and potassium may be applied any time.

Here is a link that might be useful: Fertilizing Rhododendrons and Azaleas

rhodyman,
Thanks for the information and the link.
The link is very informative.
Felix

I agree with rhodyman that healthy azaleas may not need feeding.

Here in south Georgia, the rule of thumb is to fertilize (and prune) immediately after they bloom, but no fertilizing after they set next year's buds -- end of May here. The buds may 'blast' if fertilized before bloom.

Here's a link to good Florida information. I hope you find it helpful.

Nell

Here is a link that might be useful: University of Florida Hort

I've found that it's helpful to fertilize my azaleas once every 2 or 3 years, using either special azalea/rhododendron fertilizer, or spreading chicken manure around the base of the plant. I was worried that chicken manure might have an alkaline reaction, but if it does, it doesn't hurt anything, because my native azaleas have all responded beautifully to it. Of course I wait until after they've bloomed and after all danger of frost is past before I fertilize.
MissSherry