Bark or mulch is a widely used natural ground cover by Landscape Contractors and Homeowners throughout California. Bark mulch is available in a wide range of textures and colors, from natural tan bark to colored or dyed products. When bark mulch is installed to a minimum depth of three inches under plants or landscaped areas, it helps control weed growth and helps the soil retain moisture. Bark mulch applied at a depth of at least three inches generally lasts two to three years before they need refreshing with a new layer. Although the color may change before that time, the water retention, weed prevention, and other benefits remain the same.