Winter is here, and while Victoria enjoys a far milder winter than the rest of the country, it is not without its hardships. High winds and heavy rains can lead to limb, root and even stem failures in our urban forest.
Thankfully, a little preventative pruning goes a long way to maintain the health of our trees and properties. While deciduous species (oak, maple, chestnut etc.) lose their leaves and therefore a lot of wind resistance over the winter, the many varieties of conifer (fir, hemlock, cedar etc.) keep their foliage and are more susceptible to wind damage.
Crown thinning, also referred to as spiral pruning or windfirming, is a technique used to reduce the wind resistance or “sail” of conifers. It involves selectively removing limbs in the upper canopy to provide a path for the wind to travel through the crown rather than buffeting against it. Crown thinning is also beneficial to the overall health of the tree, increasing airflow and improving structure.
Limb reduction involves cutting back long extending limbs. Trees are always reaching for the sun, sometimes this causes limbs to extend far out from the trunk and put on excessive foliage near the ends. This results in heavily end-weighted limbs that are more likely to fail under weather stresses (wind, snow). Limb reduction reduces both the sail and the surface area where wet snow would weigh the limb down.
Root failure is the worst case scenario. Cracks and/or heaving of the soil around the stem of a tree are a sign of imminent failure. The roots are the anchoring system of the tree, and if they are lifting and moving the tree is in immediate danger of toppling over. Heavy rain followed by high winds can soften the soil and compromise the anchoring of the tree to the ground. This extreme situation demands removal of the tree before it fails.
As the old saying goes “an ounce of prevention is worth a pound of cure”, and never has this been more true than in with the health of our urban forest. With a proper assessment by a certified arborist your trees can be maintained to be enjoyed and appreciated for years to come.
Conan O’Dell, Garden City Tree and Landscape