Winter injury of Northwest landscape plants
Just about the time you think your lovely new Daphne or Silk tree has finally settled into an established existence in your landscape, along comes an unexpected killing frost, knocking back all that lush growth that developed over spring and summer. Unless you anticipated the cold weather and were able to cover them or bring them out of the cold, the damage delivered by those freezing temperatures was devastating.
Unfortunately our weather patterns here in the Northwest can be fickle and unpredictable. It’s not uncommon for our temps to suddenly range from daytime highs in the 60’s and 70’s down to freezing at night in early spring and late fall. Our weather is just mild enough most years for us to be tempted to plant exotic plant species more suited to warmer, arid climates. Sometimes the roll of the dice pays off. If an otherwise exotic plant variety has a chance to acclimate slowly over two or three seasons, without a catastrophic exposure to temperature extremes, the chances of that plant surviving into maturity goes up.
Even so, a deep cold snap at the wrong time, accompanied by bright sun and drying winds, can be a recipe for damage or death even on an established non-native tree or plant.
One of the issues we observed in landscapes in our care this fall was a hard frost before deciduous trees had a chance to finish the senescence process. This disrupted the usual reallocation of nutrients from leaves (right before leaf drop), to roots, depriving them of their last meal of the season. All the more reason for supplemental fall fertilizer applications. (Wolbert’s SuperRoots!)
Here is a very informative article by WSU extension experts, explaining the finer complexities of winter damage in the northwest: