If your ornamental grass has a dead spot in the middle (doughnut), the normal way to fix the problem is to dig and divide the grass. If you have ever dug up a large ornamental grass, it is not an easy task! Here is how to fix the problem. Use a reciprocating saw (saw saw) with a twelve inch blade. Stick the blade down into the ground and cut out the dead center. With a spade dig out the dead center and remove it. Now refill the hole with fresh soil. The grass will refill the center over a couple seasons.
The Creative Gardener
The Creative Gardener