mulch mulch mulch mulch.
Compost will do, or horse poo, or chicken poo if rotted down, or cocoa shells, or bark, even grass cuttings under established shrubs.
A good four inches will do, suppresses weeds and saves water.
Even gravel works, but I don't like gravel, or those slate chips, they're too ornate and fussy and that way leads to gnomeland or stupid Easter Island statues.