WINTER PLANT DEPRESSION REDUX

Feb, 10, 2019: Almost five years ago, to the day, I wrote a blog post (Winter Plant Depression) on dealing with snow loads on trees and shrubs. Looking out over a snow stomped landscape once again has inspired me to re-echo my call. The snow is coming! The snow is coming! As Paul Revere might do if he had a Sno-cat.

Here is western Oregon, particularly the Coast range where I live, when we get snow its heavy and wet. We may not get the volume of snow of New England or the upper Mid-west, but I challenge any of them to produce a heavier snow per inch than we have. That’s because most of the time, when it snows, temperatures hover just below freezing. The colder the temperature, the lighter the snow.

Our snow are limb breakers and benders. Not all plants respond the same to snow load. Conifers tends to fare better (arborvitae excluded). They have adapted a branch structure that bends downward with weight and more easily sheds the snow before breaking, Even among our local conifers, there is some variability in snowload tolerance. Western hemlock and noble fir have greater tolerances than Douglas Fir. Saplings fare worse than mature trees. Deciduous trees with their upright branch structure seldom bend as well and so they have greater limb breakage.

So like the Minutemen responding to Revere’s call, one needs to bundle up, grab a shop broom and go forth into the storm and start knocking snow off branches. A bent over small tree or shrub may be able to recover if the snow is shaken off a few hours after bending, but wait a day and no way.

Though snow can cause branch breakage, ice does far more damage. Ice can increase the weight of a branch by 30 times! Ice damage particularly hits deciduous trees harder in our area. Ice storms tend to be fall events for us. The earlier in the fall the ice storm usually the greater the damage. Some trees are late in shedding their leaves or some trees have corky branches, like sweet gum, and these increase the surface area for ice to accumulate and thereby increase breakage potential. The treatment for limb breakage is to prune off the broken limb back to a sound branch crotch. Time is not as critical, but within a year is a good idea.

So for many, the winter wonderland of snow makes for exciting outdoor recreation and snow angels. But for the arborist its a time of dread and a time to gird one’s loins (preferably in thermal underwear) and go forth and do battle with the storm.

F & P