Pruning at planting
Objective: The objective of pruning at planting is to prune to as close to the ideal young tree form as practical (see photo). Do not be afraid to prune for structure at planting; nurseries prune millions of trees annually just prior to, at, or soon after planting. It should be clear that pruning at planting is for structure only and not to simply remove foliage.
Pruning at planting appears to have little, if any, positive impact on transplant survival and growth after planting. However, structural defects should be corrected at planting to reduce maintenance costs later. Most trees have at least some defects that should be removed at planting; even minor defects left untreated at planting can turn into major defects later. Only small diameter branches require pruning if quality trees were purchased.
The main strategy when structurally pruning at planting is to develop a dominant leader or trunk by shortening or removing codominant stems and clustered and competing branches. Clustered and fast-growing branches can form inclusions in the branch unions which indicates a weak point on the tree. They can also choke off the leader if allowed to grow unchecked. Be sure to reduce or remove any branches growing upright that might compete with the leader later including very small ones in the top third of the tree. In addition, clean the canopy by removing branches broken or badly damaged during shipping or planting.
Do not prune the plant only to compensate for root loss. The latest research indicates that in most instances pruning does not help the plant overcome transplanting shock. Sugars produced in leaves are needed for new root growth so the more leaves on the tree the better the root growth.
If you feel that the top may die back from lack of irrigation after planting, and you would like to remove branches (leaves on palms) by pruning before they die anyway, then you purchased nursery stock too big for your irrigation capabilities. If you still feel compelled to prune field-grown trees at planting to compensate for root loose, reduce codominant stems and the largest diameter branches. Do not randomly top the tree or round it over.