Genus

• Rhododendrons and azaleas belong to a similar genus which contains nearly 900 species of semi-evergreen, evergreen and deciduous shrubs that usually bloom in spring.
  
  

Best Food for Rhododendrons

• Rhododendrons are best fed with a specially-formulated rhododendron food. They can also be fertilized with the fertilizer for evergreens.
  
  

Best Time to Feed

• Rhododendrons do not require a lot of fertilizer, and this need is often determined by the overall health of the plant. For instance, if the plant leaves are off-colored, apply the fertilizer between the middle of February to the end of April. For additional feeding use fertilizer right after the plant flowers.
  
  

Additional Food

• Yellow leaves may still remain after fertilizing. In this case apply sulfate of magnesium or Epsom salts in the middle of April. Mix a tablespoon of Epsom salts in one gallon of water. For larger plants, use two or three gallons of water and a gallon for the smaller ones.
  
  

When Not To Fertilize

• It is best not to fertilize rhododendrons during the summer. If the plants still have weak growth, few or small blossoms and weak leaf color use a 0-10-10 liquid fertilizer. Apply every month starting from July and ending in October. The 0 nitrogen level fertilizer will strengthen the plants for the winter and improve their overall health. Spray the fertilizer on plant leaves during the cooler time of day.