by Barrie Anderson
I still recall the roughly 60 foot tall Quercus Alba, (White Oak) my grandparents had on their farm. I remember being so excited as a little girl to go to their house and look straight up the trunk into the branches and let my mind wander high above. The branches were plenty and seemed to spread out forever into the landscape in my little 7 year old mind. Oh the acorns! I couldn’t wait for those to fall to the porch and base of the tree so I could load up my pockets, and plant my Oak “orchard”. I do know, however, my grandparents felt differently about the dropping of acorns.
The one thing I distinctly remember about their Oak tree, was that it had a very beautiful shape to it. The reason for that was someone many years prior had properly pruned this tree. This Oak was very close to my grandparent’s house, in fact it was nearly upon their porch, but the shape of it was perfect!
In order to attain a handsome stature, it’s critical to prune an Oak early in its life. This is what is called developmental pruning. It’s done when the tree is very young to encourage proper growth as it develops in your landscape. Once an Oak reaches maturity, it’s long past time to prune for proper growth. The sheer size of an Oak will make any amount of pruning an intense challenge. Pruning Oaks must be done at the correct time of year in order to avoid disease. Only prune your Oaks from December to March when the tree is dormant. The fungi aren’t out and about and this also allows the Oak time to rehabilitate from the pruning. No matter how precise and clean your cut is, it is still a wound to the tree. It’s imperative to not cut into the main leader when pruning as this destroys the protective cells in the branch collar preventing them from engaging in the healing process. A nearly flush cut to the leader is required for proper recuperation from the cut. (See photo below left). It’s also essential to not cut too far away from the trunk because this leaves a stub, acting as a direct highway, which allows disease to enter the tree and prevent those protective cells from mending the wound. In the picture below right, you see where this homeowner left stubs (circled in red). Leaving a stub and or slicing into the leader, is very damaging. Once healed, your Oak will have a perfect callus on its trunk. Do not paint over the area after you prune as it actually impedes the recovery operation.
Another critical item to consider when pruning, is making certain there is a dominant leader. The leader is the vertical stem at the top of the trunk that allows for the scaffold branches to grow and form the canopy of the tree. Scaffold branches should be at a 45 degree angle from the main leader creating what is called a U shaped crotch. Prune out any crossover branches and random water sprout branches as those interfere with proper growth. You can see in the picture below the central leader, scaffold branches as well as crossover branches, which are the branches outlined in yellow.
There you have it! Prune judiciously, and often when your Oak is young and you will have a statuesque, handsome, specimen in your landscape for many years to come!
Photos courtesy of K. Messinger.