EarthBox Mulch Cover: Black/White Reversible When used on the EarthBox, the mulch cover stops weeds and conserves water. There's no need for herbicides, and it protects growing environment from rain or drought. Once in use, these covers are good for an entire growing season. Reversible Black/White mulch covers are sized just right for both 1st generation and 2nd generation (manufactured after 11/2005) EarthBoxes.