The Tri-State region in southwest Ohio experienced an ice storm overnight this past Wednesday. Although the official accumulation of ice due to freezing rain reported at the Cincinnati-Northern Kentucky International Airport was only 0.22", the number of homes and businesses in Greater Cincinnati without power yesterday morning exceeded 200,000. Why such a high impact from only 1/4" of ice?
Of course, the actual accumulation of ice on trees and power lines varied widely throughout the Tri-State region; some locations saw more, others less. However, the other reason – perhaps the most significant reason – for such a high impact was the time of the year. With many trees and shrubs are still holding onto a high percentage of their leaves, the impact was very different than if the ice event had occurred in February.
The ice load produced both branch breakage as well as fallen trees. Cincinnati parks received reports of nearly 100 downed trees throughout the city.
However, the reason for this BYGL Alert is not just to report the most dramatic effects, but also to mark the event so ice loading will be considered when diagnosing branch dieback in the region next season.
Woody stems bent by heavy ice or snow loading may not break, but the vascular connections within the stems may be compromised. The effect won't become apparent until the loss of vascular continuity produces leaf wilt and branch dieback next season.
More Than a "Pear Storm"
Certain Callery pears (Pyrus calleryana) such as 'Bradford' are notorious for weak stem attachments. After a relatively light wind event a few years ago, Kevin Griffin (Acme Tree and Landscape Service, Inc.) shared with me that he and his family of arborists describe wind, snow, and ice storms by their impacts on Callery pears. Thus, he calls light events that produce limited damage "pear storms." It's an effective storm-rating yardstick.
However, during a phone conversation today with Kevin (as he was buying gas for chainsaws!), we both agreed this was more than a pear storm. A wide range of trees and shrubs that were affected including those that are retaining their leaves as well as some, such as river birch, with ice accumulating on large numbers of small stems.
While Callery pears certainly accounted for a high percentage of the damage as well as some of the most dramatic stem breakage, the ice load also produced considerable damage to oaks, maples, birch, elms, white pines, and baldcypress. Even one of my viburnums was broken apart.
Again, although the stem breakage is currently apparent and often dramatic, the long-term impact of hidden vascular damage may linger into next season. The time span between cause and effect can challenge even the most experienced diagnostician.
SPECIAL NOTE:
Sadly, Boone County Arboretum Director, Kris Stone, is reporting that half of their collection of over 3,600 trees and shrubs experienced some sort of ice load damage with 10 to 15 percent receiving severe damage. This horticultural gem is located in northern Kentucky just south of Cincinnati. Readers may note the Arboretum hosts one of our Greater Cincinnati BYGLive! Diagnostic Walk-Abouts.
Kris is asking for help in the coming weeks, perhaps even months, from our tree care community in helping the Arboretum recover from this devastating event. If you can provide assistance after responding to the needs of your clients, please contact Kris at: Kstone@boonecountyky.org
