Most pomegranate growers in California grow multiple tree crops and determine their spacing based on the spacing of adjacent orchards to use the same machinery (Day and Wilkins 2011). A primary factor determining orchard design for all growers is the shape and pruning style used. Pruning is recommended for both early tree training and in mature trees (Ferguson et al. 2008b). If the tree will not be shaped into hedges or rows, increased spacing is required.
Close spacing is not preferred because excess shade can limit fruit color development, increased likelihood of fruit scarring, and less space for hand harvesting, pruning and the use of large machinery (LaRue 1980). Pomegranate trees are currently grown with as little spacing as 1.5 m in-row and 3.6 m between rows, with wider spacing at 4 to 5.2 m in-row and 5.8 m between rows (Day and Wilkins 2011). However, UC recommendations suggest planting at 3 to 5 m in-row spacing and 5 to 7 m between rows.
Planting pollinizer trees with cross-pollinated cultivars is also suggested within the orchard. If the selected pollinizer cultivar produces marketable fruit, it should be planted at a 1:1 ratio with other cultivars. If the selected pollinizer does not produce marketable fruit, it should be planted at a 1:9 ratio with one pollinizer tree in the center of a 3x3 square of the target cultivar (Ferguson et al. 2008a). However, some cultivars may also need cross pollination and pollinizers to increase fruit set and size.
More information regarding orchard establishment and pruning can be found at: http://ucce.ucdavis.edu/sites/pomegranates/files/122803.pdf and http://ucce.ucdavis.edu/files/datastore/391-575.pdf