Dwarf citrus trees in high density plantings

Dwarf citrus trees have the potential to be used in high density plantings that will have greater yield duringthe first few years after tree establishment, and be easier to care for and harvest as the trees mature. Dwarfcitrus may be obtained by management practices that restrict growth of standard cultivars or by geneticdwarfing traits of the scion, interstock, or rootstock. In this workshop, detailed information will be presentedon the characteristics of two new USDA-ARS size-controlling rootstocks, considerations in the design andmanagement of high density plantings with dwarfing rootstocks, and the trends in commercial use in Florida. The workshop will also include an overview of rootstock effects on tree size, the potential for producing dwarfcitrus trees through the use of a dwarf scion, and management techniques that could be used to restrict treegrowth and thus produce dwarf trees for use in high density plantings. Additional information on dwarf citrusand high density plantings will be presented by workshop attendees. The challenges and benefits associatedwith dwarf citrus trees in high density plantings will be discussed. Genetic restriction of fruit tree size is most commonly obtained by using a size-controlling rootstock. The mostwidely recognized citrus size-controlling rootstock is 'Flying Dragon' trifoliate orange (Poncirus trifoliata), and thisrootstock is currently used to a limited extent in many citrus growing areas to establish high density plantings. Genetic transmission of the dwarfing trait to progeny of 'Flying Dragon' has been reported, and many hybridshave been produced and tested. Two hybrids of mandarin with 'Flying Dragon' have been released by USDAARSfor commercial use in Florida over the last five years. US-897, a hybrid of Citrus reticulata 'Cleopatra' ×'Flying Dragon', was released by USDA in 2007. This rootstock combines the induction of dwarfing on the graftedscion, along with the induction of good fruit production and fruit qua