http://www.springerlink.com/content/pl8134886l6u7k35/fulltext.pdf

Breeding objectives

winter hardiness ( late bloom and deep dormancy )

Apricots are planted in solid blocks if self-fruitful, at spacings of up to 20-24 ft between trees and rows. They are trained as open center trees. Generally, all new growth and interfering wood is removed each year, exposing the spurs to maximal sunlight.