Go Organic

• Organic fertilizers offer shrub roses steady, consistent feeding, whereas the less preferable synthetic fertilizers may feed inconsistently, leaving the rose stems weak.
  
  

Testing

• Request a soil-test kit from the local county extension office. Have the soil tested to provide an in-depth analysis to be used for selecting the perfect fertilizer.
  
  

Ph Levels

• Knockout roses thrive in a pH level of 5.5 to 7.0.
  
  

Correcting Ph

• Soil that tests with a pH level of 7.5 or higher will need added sulfur, while soil that tests below this pH level will need a fertilizer higher in lime.
  
  

Application

• The texture of the soil will help determine the frequency of fertilizer application. Fast-draining soils will require more frequent applications due to nutrient runoff.