Best known as a widely used commercial rootstock. It combines grapefruit vigor with poncirus hardiness and disease resistance, making it one of the most important rootstocks in modern citrus production. Although 'Swingle' was originally hybridized by Swingle in 1907, experimentation with it as a rootstock did not begin until about four decades later. Trials were planted in Florida by personnel from the Subtropical Horticulture Laboratory in Orlando and in Texas by USDA personnel including Bill Cooper, Ed Olson, Heinz Wutscher. To Heinz Wutscher must go much of the credit for developing 'Swingle' into the widely used rootstock that it is today.