Answer: The ornamental grasses, like lawn grass, need ample water and fertilizer to grow their best. Deep supplemental watering during dry spells can be helpful, as can a slow release fertilizer such as 10-10-10 applied in the spring, along with a top dressing of good quality compost.
You may also find that after a few years they need to be divided. If this is the case, they will be growing in a sort of donut pattern with a bare or thin center and most of the current growth around the perimeter. (The time to divide is in the early spring.)
I hope this helps you trouble shoot.
Q&A Library Searching Tips