Slow-Release Fertilizer

• Fertilize your azalea plants with a slow-release granular fertilizer. Slow-release granular fertilizers contribute nitrogen slowly into the soil. Because azalea plants have shallow root systems, they can burn up from the nitrogen if you use a liquid fast-release fertilizer. Nitrogen contains salts, which dehydrate the plant. If the margins of your azalea plant's leaves look scorched, you know that you have used too much fertilizer.
  
  

NPK Amount

• Use a balanced fertilizer with an NPK of 8-8-8. A well-balanced fertilizer prevents burning and will not cause a flush of growth. Azaleas encouraged to grow too quickly from a fertilizer high in nitrogen are at risk for becoming stressed. Stressed azaleas have a higher risk of contracting a fungal disease or a pest problem.
  
  

Timing

• Fertilize your azaleas in the early spring and summer. Wait for the last threat of frost to pass before fertilizing. Split the recommended amount into two separate fertilizer applications. By fertilizing twice, you prevent encouraging a flush of new growth at once. Avoid fertilizing in the late summer, fall or winter. Fertilizing late in the season can encourage new growth that cold winter temperatures can damage.
  
  

How to Fertilize

• Measure out the amount of fertilizer you want to use. Spread the fertilizer on top of the mulch underneath the azalea's drip line. The drip line is the area directly underneath the shrub's outermost branches. Make sure that you have spread the fertilizer evenly. Water the azalea after fertilizing. Wipe off any of the fertilizer that splashes or gets on the stems and foliage to prevent nitrogen burn.