My answer is, "It depends."  Do your shrubs look healthy?  Are the leaves the color they should be or are they washed out.  Are they growing normally?  If everything seems good, then you do not need to worry about fertilizing.  They are probably getting nutrients from the fertilizer you put on your lawn or garden.  If they are struggling and have full sun and are watered on a routine basis, then they would benefit from some granular fertilizer worked in around the base.