Azaleas are a species group of flowering shrubs belonging to the rhododendron genus. They enjoy acidic soils, nutrient-rich soil and light applications of organic fertilizer or azalea and camellia food. Chemical fertilizers can be tricky to use, as azaleas are extremely shallow-rooted. Over-fertilizing to the point of damage and death is easy to accidentally do. Always err on the side of less, and more gentle, fertilizer--rather than too much fertilizer--when caring for azaleas.
Top-dress the soil surface around your azaleas once a year with organic fertilizers such as compost and well-aged manure. Spread several pounds around the base of the shrub out to the drip line. Water in the compost and manure well before applying the annual layer of mulch.
Apply a commercial azalea and camellia food once a year if needed to green the foliage. Feed immediately after seasonal flowering according to the label dosage recommendations.
Water in the fertilizer well to distribute across the soil surface, and percolate down for the deeper roots as well.
Mulch around the base of the shrub with a blanket of organic material starting 6 inches to 1 foot out from the main trunk and continuing to 1 foot past the drip line. Use shredded bark, cocoa bean hulls, leaf mold or compost in a layer at least 3 inches thick. Replenish the mulch each year as it degrades into (and feeds) the soil.