Is it necessary to fertilize annuals growing in containers?

Question:

Is it necessary to fertilize annuals growing in containers?

Answer:

Plants in containers need to be fertilized on a regular basis as nutrient levels in potting mixes quickly fall due to absorption by plants and leaching during watering.  

Many commercial potting mixes contain a slow release fertilizer.  However, slow release fertilizers seldom last the entire growing season.  When using a potting mix containing a slow release fertilizer, begin to fertilize plants when plant growth slows or the color of the foliage fades.  A granular fertilizer can be applied to the soil surface or plants may be fertilized with a water soluble fertilizer.  Check the product label for application rates and frequency.