Rapid Rooters are the newest addition to the starter cube family. Used by commercial growers for years they are now available to the general public. They are 100% organic and work great. Made from composted tree bark and latex (natural rubber). The composted bark gives off a natural rooting hormone that helps promote rapid rooting. These starter cubes also have large quantities of beneficial microbes that colonize young roots and help young plants to resist disease while maximizing nutrient uptake.