The central portions of several of my ornamental grasses are dead. Why?

FAQ
Question: 

The central portions of several of my ornamental grasses are dead. Why?

Answer: 

The centers of ornamental grasses often die as the plants get older.  When this occurs, it’s a good time to dig and divide the grasses.  When the grasses begin to grow in spring, dig up entire clumps, cut out and discard the dead center portions of each clump, cut the outer portions into sections and replant.