Branches to Roots: Preparing Pittsburgh's Urban Forest for Future Storms

By Meg Cerveny

A fallen tree on top of a parked car along Forbes Avenue in Squirrel Hill.
Photo Credit: KDKA-TV’s Chris Hoffman

On the afternoon of Tuesday, April 29th, our region experienced a storm unlike any other. The swift moving storm produced a wall of strong wind and affected the entire region within a matter of minutes, catching many communities off guard. Some areas reported gusts from 70 – 90 miles per hour. For reference, Category 1 hurricanes have sustained winds between 74 and 95 miles per hour. This unprecedented storm could become more commonplace in our area and I’d like to inform you about some approaches to managing our urban forest for resilience.

I’m Meg Cerveny, Senior Arborist at Tree Pittsburgh and a Pittsburgh transplant, born and raised in Miami, Florida. I hold a certified arborist distinction and I am eager to share my knowledge about trees and storms. Having directly experienced multiple hurricanes, including the strongest to hit the U.S. (Andrew, 1992), and worked through numerous aftermath cleanups (including the four hurricanes that crossed Florida in six weeks in 2004 while I was in utility forestry), I witnessed firsthand the impact of storms on trees and infrastructure. I want to share the lessons from that intense period.

Because this topic is near and dear to me and requires multiple pages of writing, I will touch on some overarching themes for this post:

Uprooted trees during strong storms can be minimized.
Limb failure during strong storms can be minimized.
Trunk breakage during strong storms can be minimized.
Trees and powerline conflicts are unavoidable.
The goal: Proactively plan and make tree care decisions with storm resilience in mind to minimize damage.

How? That’s the hard part.

First, let’s visualize a tree’s full extent by imagining a stemmed wine glass on a plate. The wine vessel represents the “canopy,” the stem the “trunk,” and the flared base the “root flare.” The plate around the base illustrates the “feeder root” system, which extends 2–3 times the root flare. The root flare is mostly within the top 6–12 inches of soil and is crucial for nutrient uptake, carbon storage, and stability. Picture this structure for all established and establishing trees.

All trees must adapt to their surroundings. Forest trees have the benefit of growing together, like the buddy system. Other tree branches and roots will feel and respond to the same wind and buffer it all the way down to the forest floor, thus slowing the wind speed as it hits lower branches and understory trees and shrubs. Forest trees also have the benefit of root systems that overlap and extend far distances from the trunk. Trees have evolved to live in communities, and this factor is one way they have adapted to withstand storms.

Urban trees are often more isolated, lacking these canopy and root system interactions. They also face underground limitations and human-induced stresses like small planting spaces, compacted soil under sidewalks and roads, root and trunk damage from construction and maintenance equipment, and overall soil compaction that restricts air and water for feeder roots. These factors combined create weaknesses during major storms, far removed from the conditions trees have evolved to thrive in. Therefore, urban trees need our help to overcome these challenges and stand strong

Some lessons learned from ten strong storms (mostly hurricanes) that toppled trees include:

Age of tree: Older trees have a higher failure rate, though not all do, depending on various factors and historical management.
Species of tree: Some species are incompatible to some planting locations, are naturally prone to decay, or have poor branch attachments. We should plant fewer of these near roads and powerlines.
Site history and cultural practices: Human activities and site conditions can weaken trees.
Storm strength and wetness: Saturated soils reduce a tree’s ability to grip the ground, leading to toppling even in healthy trees. Manage canopies and root systems in windy locations.
Planting in groups (3–5 or more): Group plantings allow canopies and root systems to work together to reduce wind force on individual trees.Understory trees/shrubs should be included in this strategy.
Proper structural pruning (max. 30% canopy/year): This promotes strong branch attachments, allows interior wind movement to encourage reaction wood, reduces over-extended limbs, and develops a central leader with smaller attached branches. Avoid “lion’s tailing,” topping/heading/”hatracking,” and over-lifting.
Limit trunk pruning cuts: Trunk pruning cuts can create decay columns. Multiple wounds can coalesce into large cavities. Avoid removing too many branches close together.
Maximize non-compacted root area: Healthy root development follows favorable environmental conditions. Apply 1–3 inches of mulch to help rebuild compacted soil and keep it away from the trunk so the bark stays dry
Limit root flare and surface root damage.
- Do: check for, and remove, girdling roots on trees when they’re still young.
- Avoid: cutting roots within 10’ from the trunk, cutting more than 50% of the roots, volcano mulching, hitting trunks with mowers, string trimmers,cars and heavy machinery

While we can’t change the past for our mature urban forest, this knowledge helps us prepare for inevitable future storms. Even if major storms here aren’t as frequent as they are in the southeast United States, taking proactive steps now can protect our future forests. And we have the power to grow our younger urban forest with proven methodologies that are shown to limit tree mortality and property damage during storms.

If more follow-up is requested, consider joining the CONNECT Canopy Alliance Cohort! Sign up at this link. We are a group of staff and volunteers from local governments, shade tree committees, and nonprofits coordinating across jurisdictions to grow and maintain Allegheny County’s tree canopy. Meet the partners, discuss your community’s priorities, and talk about storm response at our upcoming meeting on May 29, 9:00 AM to 11:30 AM at Tree Pittsburgh (32 62nd St, Pittsburgh, PA 15201).

Meg Cerveny will be available to answer questions at the May 29th meeting and is reachable via email at meg.cerveny@treepittsburgh.org.