Pruning trees is a historic practice serving many purposes. These purposes include tree health, longevity, aesthetics, and safety.

However, some people wonder, “Trees are natural and alive, why do we need to prune them? Why don’t we leave them alone and let them do what they naturally do?”. It’s a matter of context. Yes, trees are alive and grow naturally, but the maintained landscapes we live in are far from natural. Maintained landscapes contain living and natural elements like grass, trees, and plants, but they are not in a natural context. In nature, a solitary tree would rarely be seen growing in the midst of a pristine field of Kentucky Blue Grass. In our maintained landscape spaces, natural things are put together in unnatural ways.  This isn’t necessarily bad, it’s what we humans do, and it is important to understand these differences in contexts.

Trees look different in natural contexts, which is illustrated by a walk in the woods. In nature, pine trees will often grow tall and skinny, while in the maintained landscape the same type of pine tree will grow wide and full. Because of the dense foliage of the forest, trees have to compete for sunlight, causing them to seek light by focusing their growth vertically. In maintained landscapes, a solitary tree has all the sun and space it could ever want, causing it to say, “Hey, I can grow vertically and horizontally!”. This is where tree training pruning practices are necessary.

Trees growing in the forest focus their growth vertically to compete for sunlight | Photo Jake Louwsma

 Tree pruning in the landscape has two main goals: training and maintenance. For the purposes of this post, the focus will be on training.

Training trees is geared towards younger trees, which lays the foundation for the rest of their mature lives. The goal of tree training is to train the tree to mature with proper form. Proper form is aesthetically, but it is also important in the long-term life and health of the tree. Perhaps the most important aspect of training trees is establishing a “leader”. A leader is the single dominant top branch that grows vertically and establishes a single dominant trunk for the tree. When pruning for leader establishment, the tree is being pruned to mimic what happens naturally in the woods. In nature, sunlight is so scarce that the tree can only afford to support one dominant leader while growing. In the maintained landscape, solitary trees have unlimited sunlight and space to grow in all directions at the same time, causing them to grow multiple leaders. If multiple leaders remain, the tree will mature with poor structure. The most common illustration of poor structure is a trunk that splits into multiple large trunks (also called lateral branches) towards the bottom of the canopy. These multiple trunks will continue to mature and grow larger over time, potentially creating a hazardous situation where one of these large trunks could fail and break off resulting in injuries to people, vehicles, or structures.

Example of co-dominant leaders in a linden tree | Photo Jake Louwsma

An oak tree after a large lower limb failed. The height, size, and shape of this wound suggests this had been a co-dominant leader | Photo Jake Louwsma

When considering tree pruning, it is important to understand the context of the pruning, as well as the setting and objective. At times pruning may seem overly aggressive, while at other times it may seem insignificant. It is important to understand that the intent is to form a tree which will be aesthetically pleasing, safe for people and property, and has a long life.

Jake Louwsma CLP | Sales and Marketing Manager
Posted 4/14/2022