College Park, MD (July 29, 2013) – While most urban trees can survive a storm, more acute natural events can wreak havoc on them. Although trees are engineered to withstand normal weather conditions, some storms can exert extreme forces, resulting in tree injuries of varying degrees and tree loss. Here’s a roundup of some of the best guidelines for sparing urban forests, responding to specific tree damage following violent storms, and news on how recent storms are turning Minneapolis into a lab for why trees fall.
According to Lindsey Purcell, Urban Forestry Specialist at Purdue University, in his recent article for Purdue Extension, “Trees + Storms,” the response to tree damage following violent storms should be based on two concepts: risk and sustainability. If the tree is an imminent or likely danger to people, property or activities, the decision leaves little room for options. However, if the residual risk from the damage is determined to be of an acceptable level and the injury to the tree not life-threatening, mitigation may be possible to save the tree and reduce the danger.
Assess and Inspect Trees
Purcell describes several types of tree damage from violent weather and how to assess and inspect a tree post-storm. Common damage includes:
- Wind Throw – Entire tree is “pushed over” by high winds.
- Crown Twist – Uneven wind loading on a lopsided tree crown produces a damaging twist on major branches and the stem.
- Stem Failure – Trees fail at their weakest point. Areas of old injury sites or wounds on tree trunks can lead to tree failure under excessive loads.
- Root Failure – Roots that are restricted, diseased, or damaged can cause trees to lean and fall.
- Branch Failure – Tree branches are easy victims of loading forces. Because branches can sometimes be poorly attached to the main stems, they can easily experience injury.
At University of Minnesota, damage from a June storm is providing researchers with a crash course in treefall. With fresh evidence of 3,000 downed trees, Minneapolis is an ideal laboratory for a $30,000 study approved by the city’s Park and Recreation Board.
While cities across the state are still dotted with toppled trunks and heaved-up root balls, researchers are scrambling to document patterns that might reveal why some trees fell and others didn’t. For example, understanding whether trees rooted in tight spaces in urban boulevards are weakened by sidewalk, street, sewer and other public works projects, and ultimately change how those projects are managed and even how urban landscapes are designed.
The study could lead Minneapolis and other communities to remove and replace older trees as part of street and sidewalk projects to reduce the number of storm-vulnerable trees lining city streets. Cities might even move sidewalks next to streets, eliminating boulevards but creating more space in the public right of way so trees would be at less risk from snowplowing and other work. Learn more.
Prevention is the best way to reduce tree damage and loss. Purcell documents several prevention activities to minimize injury to trees. This includes avoiding staking newly planted or young trees,functional pruning, and inspecting trees for broken, dying, diseased and dead branches each year. Under no circumstances should a tree be “topped” to prevent wind or ice damage. And, don’t try to “wind-proof ” the tree by thinning out branches.
A healthy tree is the best defense to any challenge the tree may face in its lifetime. Appropriate watering and fertilization improves root growth and structure, making the tree more stable. Monitor for pest problems and treat when needed to prevent insects and diseases from weakening tree health. Remove diseased branches, as needed, to minimize spread and potential damage.
Storms Over the Urban Forest– Part I: Natural Hazard Management Planning offers tools to properly prepare for and respond to the threat of major storms, beginning with a “right tree, right place” approach for planning prior to planting. Coordinated efforts among city leaders and urban forestry managers, including elected officials, nonprofits, municipal agencies, utilities, tree care companies, and citizen foresters, can also help minimize damage by and to trees during storms and other weather events.
Safety is paramount when responding after a storm. Stay clear and look for dangerous hanging limbs, broken branches and other failures before beginning cleanup or inspections.
This is followed by damage assessment. Purcell also recommends matching skills with the situation when it comes to reparation of damages and restoration. Be able to recognize when tree damage requires advanced training and is best handled by an arborist.
Storms Over the Urban Forest– Part II: Post-Event Response offers guidance for successful tree revitalization after a storm. Residents’ responses to trees downed by hurricanes, tornadoes, or ice storms can vary from fear of replanting to impassioned calls for immediate replacement. Government, private, and nonprofit partners are all needed to distinguish between immediate responses and fully developed recovery plans that evaluate damage, assess community needs, and ensure best practices for replanting.
Trees + Storms
“Storm helps turn Minneapolis into a lab for why trees fall,” Minneapolis Star Tribune