Introduction Dwarfing rootstocks have the potential to increase profitability of tree-fruit growers by providing smaller trees suitable for high density plantings. Although the initial installation cost can be 10 to 30 times more than lower-density plantings, the long-range returns can far exceed the traditional plantings. However, to be viable as a commercial rootstock, dwarfing rootstocks must be adapted to a range of agro-climatic conditions, moderately disease resistant, high yielding, and produce quality fruit.