Selective herbicides are not available to eliminate undesirable weeds and not damage the ornamental grass. Eliminate weeds before planting and use a mulch to discourage them. If the leaves are not a normal color, it could indicate low nitrogen, low soil oxygen, inadequate draining or over watering. Flopping grass often indicates over fertilization. The most important care factor is to cut back foliage to 6 inches in late winter or early spring before new growth appears.
Grasses are fairly disease resistant.
However, as they become more popular, increased problems could develop. If they do, cultivar selection will become more important. Grasses don't have to be divided for many years until they form an empty center. When you divide most grasses, do so in fall, late winter or early spring. Many gardeners harvest grasses to dry in the winter for inside displays, such as pampas grass to place in tall urns.