Use mulch on potted plants too. So mulch is good. HGTV Ideas went to the experts for some answers. The Anasazi Indians in the ancient Southwest successfully gardened in arid land, thanks to the gravel and rocks they placed on the soil's surface. Use those mulches in fixed landscape beds that you don't plan on redigging and replant-ing.
Small gravels migrate easily, working their way down into the soil.
Even fairly large rock or brick nuggets can wash or get kicked out of their landscape beds. No matter what kind of soil you have, an organic mulch is bound to eventually improve it, even if it never gets turned in. It does good things for poor soils of almost any type. If the mulch stays on top, the change will happen more slowly, but earthworms and microorganisms will slowly break it down and mix it in. And of course every time you disturb the bed in any way, such as when you're planting annuals, it happens much faster.