Pruning Methods: What is Crown Thinning?

Structural Pruning is considered the best way to thin trees.

Structural pruning is the pruning of limbs and branches to promote structure which is the framework of your tree. The objective is to promote strong branching habits, in a way to prevent failures throughout the canopy for long-lasting trees in the landscape. This includes crown thinning, to reduce density evenly throughout the crown without changing crown size or shape. Entire tree crowns are commonly thinned because homeowners believe this is what should be done to trees, or they like the appearance of a thinned crown and in my opinion, this is ok to each is own, some believe that thinning somehow improves tree health, or think it is a normal pruning practice and unfortunately it is. I go into areas throughout the Bay Area and look at what some companies do, and well it’s ridiculous. But we have to remember sometimes it’s a client request.

Thinning typically does not change the overall size and shape of a tree. Thinning the entire crown without addressing the structure accomplishes little merit in terms of tree health, structure, and longevity and often wastes precious resources for both the tree and owner.

Crown Reduction

Crown Reduction is pruning to reduce the height or spread of a tree. The objective of reducing crown dimension includes providing clearance for building, streetlights, or for view; reducing the risk of tree or branch failure; reducing the amount of shade beneath a tree; mitigating broken branches when restoring following storms; preserving mature trees; or when the customer simply wants the tree to be smaller.

Pruning Precautions

Unfortunately, many people prune when it is not necessary, or they misapply or misunderstand pruning, and subscribe to the practice of only removing branches from the interior of the crown. This is often referred to as lions-tailing, over lifting, over thinning, stripping out the interior, or cleaning out. Little or nothing is removed from the ends of the limbs, and this is a mistake. In most cases, this is where the majority of the work is needed. Lion-tailing causes structural weakness, so to strip a branch of all its foliage and leave a little green at the end is not a good practice. All the work just performed is going to grow back in a couple of years depending on how drastic the interior is cleaned out. In most cases, it just puts the tree in production mode and grows back even faster.