WINTER PLANT DEPRESSION

February 12, 2014: Are your plants depressed? It's been a tough winter this year in western Oregon and, with the recent heavy snows, it's easy for your plants to start feeling depressed. But, before you start imagining me wearing a tin foil hat, I'm not talking about the mental kind of depression, I'm talking about the snow-bending-down-limbs kind of depression. This kind of depression, if left untreated, leads to limb breakage or permanent deformation.

As I gaze out at the 14" of snow that's fallen on my place, it's interesting to notice how various plants react to snow loads. The Douglas fir and western red cedar, as evergreens, catch a lot of snow and the branches are heavily laden and bending severely down, but their limb structure is such that they can do that without a lot of concern about breakage. As the snow melts and gets heavier , their springy branches shed the snow quicker than other plants. More upright branching plants, such as the Mugo pines and arborvitae in my yard, do not shed the snow very well and they end up bending and sometimes breaking. My rhododendrons seem to fare better but none are a tall (>6')upright variety, so that might make a difference.

There are whole scientific treatises, complete with gobs of formulas and graphs , written on snow and ice loads on trees. I've waded through one of them and, trust me , you don't want to go there. But , I garnered one interesting fact. Trees that are native to high snow areas, like the Cascades or the Rockies, adapt by having slower growth and greater branch deflection (droopiness, in plain English). They're built not to catch a lot of snow and shed it quickly. Many of the landscape plant materials we use have the opposite characteristics - fast growth and upright structure, which make them susceptible to the infrequent dumps of snow or ice storms we get here in the Pacific Northwest.

If your plants are depressed, the key to therapy is immediate action. It only takes a few hours of being bent over for the limbs or stem to be permanently deformed. Arborvitaes are particularly sensitive to bending. If you don't take care of them right away then no amount of pruning or propping is going to cover up the bare spot in the hedge. The prime therapeutic tool is a broom. Go out and knock the snow off the branches. (Here's where a tin foil hat is handy as it sheds snow well and, should you become buried, it's easier for rescuers, but not aliens, to see the shiny cone.)

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.

I originally started off this blog entry with the short intent to tell to knock the snow off your bushes, but I've gotten carried away and now it's sounding more like some longwinded scientific treatise, which it wouldn't properly be with graphs. So here's my graph:

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