As we stated earlier in this article, it is imperative to trim back perennial ornamental grasses if you want them to continue to look tidy and encourage new growth. Failure to trim back will cause the green to start growing through the brown, which is not a good omen. Subsequently, it is an issue because the brown will begin to produce seeds. Once the grass starts creating seeds, there is an excellent chance that the grass will die out. So, it would be best to avoid this problem beforehand by ensuring you trim your plants adequately and at the right time.