Permanently clearing an area

This may be a stupid question, but...how to permanently clear an area of resources? So I've built a wall around an island, and I know putting down foundations will clear the area, but it's annoying to see all of the bushes and tiny saplings constantly popping up. Is there a way to permanently remove these things? Like can I just have the floor of my island be grassy?

EDIT: Follow up question--how to I stop animals from spawning on my island? I thought if I walled everything off, they'd stop spawning inside of it.