The modern fruit tree in a commercial orchard, to survive in present-day competition, must bear heavy crops. The mechanical strength which determines whether it can hold its heavy load successfully or whether it will be broken down and become a liability to its owner is determined to a large extent by the training it has received the first two or three years after planting.
Coe, Francis M., "Circular No. 84 - Building Young Deciduous Fruit Trees" (1930). UAES Circulars. Paper 75.