Should I fertilize Bearded Iris?

Specific fertilizer recommendations depend on your soil type, but low-nitrogen fertilizers (6-10-10), bone meal, and superphosphate are all effective. A light application in the early spring when tulips are blooming in your neighborhood, and a second light application about a month after bloom will reward you with good growth and bloom. Avoid using anything high in nitrogen. 

A concise read on the components of fertilizer by Joe Lamp'l on the blog "Growing a Greener World" summarizes nicely, "For promoting good fruit or flower production, look for a middle number that is higher than the first. Otherwise, your plants will be stimulated to put out lots of nice green foliage, likely at the expense of fruit or flower production. Instead, you want the energy and nutrition of the plant to go towards the desired result, flowers or fruit, so a higher middle number is a more appropriate choice." Read the full post. 

Watch Ben Schreiner advise us on how to fertilize our iris: 

Schreiner's Iris Gardens offers a specially formulated, low-nitrogen Iris food. Click here to view.