When luxury homebuilder, Toll Brothers, proposed turning the historic U.S. Naval Academy in Philadelphia into a condo and townhouse complex called Naval Square, nearby neighbors and historic preservationists put the pressure on to keep the native 75-year-old trees in place.

Toll Brothers Project Manager Alex Saltzman agreed there was value in saving the native trees and called in Bartlett Tree Experts to develop a Tree Preservation Plan. The Bartlett team conducted a tree survey and inspection and then developed a strategy to protect them during the construction process. They also proposed a plan for providing the specimens proper maintenance following the lengthy construction process.

Over 85 London plane, oak, maple, magnolia, and linden trees are showcased in front of, and along the borders of, Naval Square. These stately trees provide a park-like setting for residents and the community to enjoy. It was these woody plants that everyone involved would be working to protect and preserve.

“While it’s still early to predict the 10 year outcome, the trees are doing really well, given what they’ve been through. They look healthy and beautiful and continued care will help keep them that way,” said John Studdy, the International Society of Arboriculture (ISA) arborist assigned to oversee work at the complex, in the densely populated Gray’s Ferry neighborhood.

Toll Brothers realized that keeping the stand of trees to incorporate with new plantings would be very aesthetically pleasing, worth the effort, and increase the property values at Naval Square.

“Everyone who visits this community is in awe of the front lawn. The trees are overwhelmingly majestic and unusual in this urban environment,” said Christine Andrews, Naval Square Sales Manager. “The trees clearly add value to the property.”

Protecting mature trees can be a challenge on construction sites, which is why a Tree Preservation Plan was crafted to reduce the loss of valuable trees. Under Studdy’s direction, the plan established tree protection zones, as well as pruning of tree crowns for safety, health and aesthetics.

“The leading cause of tree loss is damage to roots,” said Studdy. “During construction, the most important thing is preserving the critical root zone.”

Roots provide nearly all of the nutritional needs of trees. However, when trees are planted between parking areas, buildings and sidewalks, roots sometimes can’t get enough nourishment to support the crown.

“To ensure proper tree growth and nourishment, you really need to outline root zones on the blueprints before the bulldozers start rolling,” said Studdy.

“What we’ve learned is that you can’t get started early enough,” Saltzman added.

Implementation of the Tree Preservation Plan began with the Bartlett crews establishing the necessary tree protection zones with construction fencing and wood chips. These zones are important for keeping heavy construction vehicles out of key root areas where they can cause soil compaction as well as root and trunk injuries.

“Compacted soils, low organic matter and high salinity levels generally found on construction sites contribute to root decline,” said Hal Rosner, another arborist who worked on the project and has dealt with issues facing trees in urban settings for 25 years. “To protect trees, there are some more porous paving materials that can be used and stepping stones can be used instead of cement sidewalks.”

Arborists with Bartlett Tree Experts also advise clients that underground utility lines don’t necessarily have to be designed and installed in a straight line.

“It’s really important to work around the critical root zones that are outlined,” said Rosner.

Using a pneumatic device called an Air Spade™, workers excavate soil from around the base of a tree to determine how far the roots extend and then work to install barriers so that any potentially damaging construction work is kept well away from the zones.

“Anything that can compact the soil, even putting a dumpster under a tree, can cause real problems,” Studdy noted.

Bartlett Tree Experts is one of the few tree care companies that have a research laboratory staffed with Ph.D.s and other scientists. At their labs, they continually test for better ways to preserve trees during construction. One area of research is artificial soils that allow for root growth but can also support a pavement. These soils include stone or aggregate for structural base. Loam and organic matter are mixed to fill voids and encourage growth of fine roots.

“We are conducting experiments at our research facility to determine the best way to grow trees in highly developed urban areas. What we are looking for is a system that will allow roots to prosper under pavement so that we can have healthy trees and streets, sidewalks and buildings all coexisting,” said Dr. E. Thomas Smiley, who works at The Bartlett Tree Research Laboratories. “We are continually looking for better techniques to grow and protect trees in the urban environment.”

While construction was underway on the Toll Brothers project, the crowns of the trees were pruned and will continue to be monitored and trimmed as necessary. Pruning is another important part of plant health and safety as it helps keep a tree’s structure and branches sound. It also improves light flow for enhanced growth of trees and turf and adds to the beauty of the tree.

In general, after construction is complete, the arborists recommend placing a mulch buffer around trees so that mowers, weed trimmers and pedestrians are kept at bay. Wounds caused from these items can interrupt the flow of water and nutrients, making trees more susceptible to pest problems.

“Bark beetles and borers feed on bark and sapwood of stems and branches. This feeding interrupts the sap flow and can spread disease. Canker and fungi then invade the stressed trees and can girdle or kill stems and roots. It doesn’t happen overnight, so the trees should be monitored over the long haul. There’s no use spending a lot of money preserving mature trees and then letting your guard down. Treat the trees as an investment to the property,” said Studdy.

At Naval Square, the team also conditioned the soil for enhanced growth and health. Studdy and his team used Bartlett’s patented Root-Rx™ Root Invigoration process to promote healthy tree roots. This process leverages a supersonic Air Spade™ to break up soil compaction, and then incorporates organic matter and nutrients, resulting in a root growth medium similar to potting soil. Trees were also irrigated to stimulate root growth and maintain health in difficult environments.

Studdy stresses the need for proper aftercare. “This doesn’t mean loving your trees to death. Too much water, too much fertilizer and too much mulch will kill the tree. An arborist can help you put the proper balance in place.”

Rosner’s pet peeve is trying to educate landscapers and property managers about the misuse of mulch or “volcano mulching.”

“They think that this volcano of mulch placed up and around the base of the tree is good for it or somehow aesthetically pleasing to look at. It’s just plain wrong,” said Rosner. “Ideally, mulch should be applied in a two-inch layer from the base of the tree out as far as the widest branch extends or what we call the drip line, or as far as the site will allow.”

The team also used Integrated Pest Management (IPM) technologies to monitor for pests and cultural problems. Innovative treatments

including the introduction of beneficial insects and other sound cultural practices are now available to help maintain healthy landscapes.

“We’re using ladybugs in the downtown area to control aphids and other pests in an urban area where spraying is difficult,” Rosner added.

“We are experimenting with products in our labs that deer don’t like the taste of, enabling new and mature plantings to live out their full life cycle,” added Dr. Smiley. “It’s a very exciting development.”

Throughout the entire Toll Brothers project, the Bartlett team worked with Saltzman and the construction crews to provide education and understanding about how construction activities and trees can co-exist, benefiting the site long after the bulldozers have gone. Periodic monitoring continues and discussions are held as needed to address any unforeseen events and develop plans to keep the job on time and the trees healthy.   SLDT

Five Steps to Tree Preservation:

Call In A Professional Arborist
The International Society of Arboriculture (ISA) has developed various levels of certification for arborists. The first level is that of a Certified Arborist (CA). At this level the arborist has demonstrated a basic knowledge of the art and science of tree care.  The second and highest level is that of the Board Certified Master Arborist (BCMA). An arborist at this level has an extensive history of working in arboriculture and has demonstrated a high level of knowledge. Go to www.isa-arbor.com to learn more about certification and to see if your tree care provider is an ISA Certified Arborist.

Schedule A Site Visit Before The Blueprints Are Drafted
Have the Certified Arborist assess or inventory the trees on site and evaluate them to decide which trees need to be removed and which can be saved. The earlier an arborist is called in, the less need for a redesign and the more successful you will ultimately be in saving trees and saving money.

Communicate Goals To The Entire Construction Crew
A simple brown bag lunch and brief presentation can go a long way toward seeing that tree preservation plans are communicated to all workers. Effective communication early on will ensure that tree preservation costs don’t skyrocket due to an error.

Plan On-Site Visits During The Construction Process
Steering heavy machinery and equipment away from the critical root zones is key. Also, burning, grading, chemical use and dumping rubble on site contaminate the soil and puts trees at risk. This damage isn’t always apparent to the untrained eye. An arborist should visit the site twice a week or more often if necessary. Make sure you have his or her cell phone number in your emergency contact information.

Establish A Proactive Post-Construction Tree Care Program
Put a plan and budget in place that includes follow up pruning, fertilization, root invigoration and possibly lightning protection systems. When tree preservation is not planned for, the bulk of tree care dollars are spent dealing with tree hazards, dead, declining and replacement trees.