In New Orleans, live oak trees are as important to the city’s identity as its distinct architecture, unique culture, and vibrant history. Maintaining the health of thousands of trees scattered throughout New Orleans falls to the city’s Parks and Parkways Department. And that’s a big responsibility according to Hailey Bowen, PLA, ASLA the city’s chief landscape architect.

“We have many historic trees, particularly our live oak trees, and we’ve actually been involved in a lot of restoration projects,” says Bowen. “We have an urban forestry division here at Parks and Parkways and they’re focused entirely on working with the city’s canopy. We have over 500,000 trees that we manage in the city.”

Bowen entered the field of landscape architecture in 1998 and has been with the City of New Orleans since 2009. She joined the Parks and Parkways Department during the years following the massive rebuild after Hurricane Katrina. After the storm surge, many of the city’s live oaks were damaged or dying, and more than a decade later, repairing the scars of that storm remains ongoing.

Since Hurricane Katrina in 2005, the city has sought funds to restore various corridors. The destruction wasn’t limited to buildings—it included trees, neutral grounds, green spaces, and parks. The historic live oak canopy was showing serious signs of decline. Historic Esplanade Avenue was particularly hard hit. Without the grand live oaks, Bowen notes, “Esplanade Avenue would lose much of what makes it special. It’s the Creole version of St. Charles Avenue.”

In the months after the storm, trees planted along the neutral ground (a New Orleans term for a median) were damaged by floodwaters and debris from destroyed 19th-century homes. Heavy machinery rolled over the roots during cleanup efforts, and subsequent road work and pedestrian compaction further stressed the trees. “The canopies were dying back,” Bowen says. “Our arborist evaluated the trees and we were very concerned for the future of Esplanade Avenue.”

Constraints for Restoration

Restoring the grounds presented several challenges. The roots of live oaks extend close to the surface, making excavation impossible. Soil tests indicated high alkalinity, so chemical changes to the environment would risk plant health. Adding a walking path could lead to further soil compaction.

“Another one of our problems was that we wanted to restore Esplanade Avenue back to its original turf and trees,” says Bowen. “Over the years neighbors had placed house plants and garden species along the neutral ground. But the historic character was what we wanted to preserve. People have always walked down the center of the neutral ground, and we knew sod alone wouldn’t survive the foot traffic.”

Finding a Solution

To aid in the restoration project, Bowen consulted with urban forestry experts at Louisiana State University’s AgCenter in Baton Rouge, including Dr. Hallie Dozier, Assistant Professor of Forestry Extension Natural Resources at LSU. “She pointed me towards James Urban’s books,” Bowen recalls. “He’s a landscape architect, world-renowned for his work in keeping urban trees that have had a lot of human interaction stay healthy and live longer lives.”

The solution to Esplanade Avenue’s challenges was found in one of those books: expanded shale and clay. “I started reading about how the product is used in areas with root compaction,” Bowen says. “We needed something that could be applied on the surface, that wouldn’t alter pH, and that would provide structure without adding more compaction. Expanded shale and clay fit perfectly.”

Implementation on Esplanade Avenue

After two years of planning, work along Esplanade Avenue began. Crews cleared dead trees, invasive plants, and debris. Arcosa’s lightweight aggregate was specially blended to ensure good plant health and to create a structural surface for the pedestrian pathway.

“We really liked that it’s pH neutral,” Bowen says. “Our soil tests showed high alkalinity, which is a citywide issue, and we didn’t want to make that worse. Expanded shale and clay are structural—they support pedestrian activity while keeping openings for tree roots and preventing further soil compaction.”

Additional lightweight material was placed in trenches dug radially around the tree roots. Using “grow guns,” or air tools, crews opened the soil in patterns that improved oxygen and rainwater access. “No matter how much pedestrian compaction occurs, the structural qualities of the expanded shale and clay will help protect the roots,” Bowen explains.

Results

Today, a winding path made of lightweight aggregate meanders through the restored neutral ground. The health of the historic live oaks is protected, while neighbors along Esplanade Avenue enjoy a welcoming new walkway.

“It worked out well,” says Bowen. “Green infrastructure is so important. Everyone knows the value trees bring—environmentally and aesthetically. They make people happy. My personal mission on this job is to reforest the city as much as possible and protect our heritage trees, because that’s what this job is about for me.”