Structure Pruning? What?

    by Jon Farkas       

  

              The year was 1999. It was a warm spring day, maybe too warm, I was warming up for a soccer game against our cross town rivals which my Dad was supposed to come watch me play in. As I waited before the game for my Dad to show up, storm clouds began rolling in from the north. Before I knew it the sky grew dark, rain started pouring on us, and the winds picked up. The game quickly got cancelled and all the parents gathered up their children like eggs on Easter morning and drove off into the storm for home. I waited and waited and waited for my Dad to show up at the game. The parking lot was quickly emptied and I sat alone on a bench in the rain. I was ready to begin walking home when I saw some headlights coming down the road and entered the parking lot. I soon realized it was a police officer. The officer cracked the window and shouted, “Are you Jonathan?” I nodded my head and jumped in the passenger seat. He began speaking to me and told me he had some bad news for me. “Your Dad was walking your dog this afternoon in the storm and was struck by a falling tree limb, he’s unconscious and the doctors say he might not make it.” Lightning shot across the sky and a horrendous crackle of thunder immediately followed. I vowed then and there that I would devote my life to killing every tree I possibly could to honor my father’s life.

                I began devising elaborate plans on how I would rid this town of all the trees so they couldn’t hurt another person. At only 11 years old, these plans weren’t very well thought out but my drive to fight trees grew stronger as I got older. I researched day and night to learn how trees grow and where their weaknesses were. Over time I found that poor branch structure in trees is a major cause of limb failure and this problem could be corrected through structural pruning practices at young ages.

                Structure pruning young trees is the most important but most overlooked practice in arboriculture. Many limb and tree failures are predictable and correctable with early detection. A strong branch structure of a tree consists of a few key things: one strong dominant leading stem, branches of a diameter not to exceed 1/3^rd the diameter of the stem, sufficient branch spacing (not having multiple branches at one point), a pronounce branch collar and branch bark ridge, no branches reaching from the bottom 1/3^rd to the top 1/3^rd of the canopy, and no overextended or excessively heavy branches. All of these criteria can be managed for through structural pruning practices, significantly reducing the likelihood of branch failure in the future.

                Train Pruning: Train pruning is a form of pruning young trees to have one dominant leader and suppressing any co-dominant stems or branches. This is the most important pruning prescription there is. A young tree can consist of 100% sap wood, which responds to wounds rapidly. Pruning cuts on young trees are much smaller and close over much faster than mature tree pruning cuts, which significantly reduces the likelihood of infection or decay at the site of the cut. Almost any tree at a young age can gain proper structure for a long, healthy, safe life through train pruning.

                Subordination Pruning: Subordination pruning is done to juvenile trees that have been neglected of structure pruning. This is a more aggressive style of pruning and is done by reducing any competing leaders by 30% to favor a dominant leader and suppress any large co-dominant stems so the leader may grow larger while the suppressed stem stays the same size in and attempt to reach the goal of a 1:3 branch to stem ratio. This practice can cause problems with disease and decay at the point of the cuts because the tree is no longer 100% sap wood and will now have heartwood which does not seal over as readily, leaving large wounds for a long period of time. The larger the cut, the harder it is for the tree to respond and defend itself.

                Corrective structural pruning done at a young age is an easy but unnoticed art. Many people call to have their trees pruned when they get big. By this time the problems may be uncorrectable and much more difficult and more expensive to do. If neglected, trees can and will fail causing countless personal and property damage in the urban forest.