Existing plant material needs to be evaluated. Is it healthy? Does it have good uniform coloration? Is it misshapen or unsightly? Will it be an asset to your garden or a hindrance? Has it grown to its full size or will it eventually shade your sunny area? If the existing plant material doesn't fit your goals, remove it. Many people have an aversion to plant removal and attempt to work around unhealthy, unnecessary plant material. Often times, years later they wish they had pruned the darned thing at the base!
The work of a garden bears visible fruits - in a world
where most of our labors seem suspiciously meaningless.
-- Pam Brown, b.1928