When word got out last month that someone had drilled holes in the trunks of eight Chinese pistache trees on Baronne Street and poisoned them with herbicide, many wondered who could do such a thing … and why.

Architect and neighborhood property owner Peter Trapolin says he has no idea who killed the trees, but he is hardly baffled as to the likely motive.

“They are extremely aggressive growers,” he said of the trees. “They’re a totally inappropriate tree for an urban setting, and they’re causing damage to every (older) building they’re planted next to.”

Trapolin said the Chinese pistache needs a lot of water to support its broad, dense foliage, and it has an aggressive root system to find it. As the water drains from the clay soil under the often historic buildings just feet away, the ground subsides, foundations shift and façades crack, he said.

Trapolin sued the city in 2011 over the damage he said the Chinese pistache trees along Julia Street are doing to the building he owns at the southeast corner of Julia and St. Charles Avenue.

“Apparently, someone on Baronne Street thought, ‘I won’t go through the trouble (of suing). I’ll just kill the trees,’ ” he said.

Poisoned pistachio trees map _lowres

Map showing block of poisoned pistachio trees

While it’s common to hear them called pistachio trees, Pistacia chinensis is distinct from its relative Pistacia vera , the species that produces the popular nut.

According to the Urban Tree Foundation, the pistache tree is commonly planted in cities because it is drought-resistant.

Trapolin said the city has been planting the Chinese pistache throughout the Central Business District and Warehouse District beginning before the 1984 World’s Fair and, in recent years, seems to be favoring it over other options, like the ginkgo.

While he understands the decision aesthetically, Trapolin said, the city is turning a deaf ear to the owners of older buildings who are paying the price. He has a photograph of an inch-thick Chinese pistache tree root growing through the brick foundation of a building that had to have shoring work done.

“They’re tearing these buildings apart,” he said.

Trapolin said he wrote to the city and sent pictures of the damage to the Julia Street property, which he rents to FedEx. The building has cracks in the façade and has sunk about an inch compared with the adjacent sidewalk. The alley between the building and its neighbor narrows as it goes up because the building has started to lean.

“The only change in the environment since that building has been built is the introduction of these trees,” Trapolin said.

He said the city’s position is essentially that trees do not cause subsidence, and he was left with the impression that he had no other choice but to sue. The suit is pending.

The city refused to make anyone with the Parks and Parkways Department available to discuss what goes into the decision on what trees to plant where, or to talk about Chinese pistache trees and complaints about them.

“We are aware of complaints regarding trees in the (CBD) adversely impacting building foundations, but so far, those claims have not been proven,” a spokesman wrote, declining to comment further.

Trapolin said he finds the argument that trees don’t cause subsidence ludicrous.

“To me, it’s very clearly documented, and it’s been written about all over the world that trees cause subsidence,” he said.

According to an arborist’s report commissioned by Trapolin as part of his lawsuit, the Chinese pistache near his building released five times as much moisture through its leaves — water that came from the ground through a process known as transpiration — as a nearby red oak of similar size.

Brian Kempf, director of the Urban Tree Project, said there are a lot of variables that make it difficult for an outsider to evaluate the local situation, with the makeup of the soil chief among them.

Speaking broadly, however, Kempf said “all trees are going to take water out of the soil. That’s how they live. And if the soil is an expansive clay, any tree taking water from it can create movement.”

David O’Reilly, a geotechnical engineer with New Orleans-based O’Reilly Engineering, said that while he hasn’t done any work relating to tree damage in the CBD, he has dealt with the issue before and that the idea of tree-related subsidence is hardly controversial.

He said the clay soil in the area has large chunks of organic matter, and as trees suck the water out of the ground and lower the water table, it exposes that organic matter to oxygen, causing it to rot.

Trapolin said it could be that the city doesn’t want to admit any liability for fear of exposing itself to more lawsuits.

In 2009, the owner of 812 Baronne St., Lawrence Weidermann, sued the city and the Downtown Development District over property damage he said was caused by Chinese pistache trees. According to court records, the suit was settled two years later; the terms were not disclosed.

While some Baronne Street property owners said to be upset about the trees on their street declined to comment on the record, Trapolin doesn’t seem worried anyone will assume his opinions make him a suspect in the deaths of the eight trees there, particularly because the property he owns is two blocks away.

Asked if he poisoned the trees, he laughed.

“If I was going to poison trees, I wouldn’t poison the ones on Baronne Street,” he said. “I would have poisoned the ones on Julia Street.”

Trapolin said he is generally supportive of trees in urban areas and agrees they bring benefits. But he said he’d like to see better execution, including proper irrigation, better spacing and fewer Chinese pistaches.

“Everybody likes trees,” he said. “I don’t know what the right one is, but it’s not these.”

Follow Chad Calder on Twitter, @Chad_Calder.