Two in a Row!
Written by: By Tony Arnoldi, Board Certified Master Arborist WI-0102B
Every year is a little different. We make our plans for all the treatments needed to help trees through the expected stresses and onslaughts that a year typically brings. But there is always a twist, a zinger, an aberration, or an unexpected variable – a “curve ball” of sorts delivered by nature, that makes us adjust and keeps us on our toes. This year that curveball is the result of an early polar vortex blast on Halloween 2019!
Cold injury on plants can happen when the low temperature falls below their tolerated range and stay there long enough to damage tissues by freezing. Plants vary as to how low this number is. It is made worse by the timing of the freeze. Plants need time to gradually prepare for cold temperatures by moving water out of their cells, concentrating the contents of the cells to act as a sort of antifreeze. If the plants are not finished with this process, greater damage can occur. Halloween was too early for the plants to be ready for this cold and damage occurred on many. We are still noticing the effects of this on more trees and shrubs as new or extended symptoms show up.
Halloween was actually the second polar vortex because the previous winter had an even colder one, It occurred in January 2019 when plants were as prepared as they could be, so was not quite as bad a blow.
Half-hardy plants such as Japanese maple, Magnolias, Paperbark maples, some varieties of Redbud, Burning Bush and Rose of Sharon showed a high amount of injury . As trees struggled to put out their foliage it became evident that others were affected as well. Many Honeylocusts and Pears displayed dead branch tips. Silver maples, Ash, Black locusts and some Lindens took longer to fully leaf out. Many Northern pin oaks in the northern forests were damaged, some were even killed. The list is still being added to. Not all individuals of a species were affected as it mattered what exposure, wind direction and other variables (of each micro-climate) there were.
Pruning out the dead and damaged branches will be necessary. Also other care to help plants recover from this damage may help as well. Call your Wachtel Tree Science Certified Arborist to help assess and determine appropriate care strategies to preserve your trees.