Grasses sway in the breeze and add movement to a design.  They also give a planting a seaside or natural look.  Because grasses are cut back in the early spring, it is the only time they do not look good.  When the foliage emerges in spring is look vibrant.  As the summer moves along they look better and better and many varieties send up flower plumes by late summer or fall.  The foliage loses color when the cold comes, but most varieties look great even in winter.