In the Urban Forest of San Jose there are many street trees, many problems

By Bruce Newman
San Jose, CA (February 2, 2010)- The two sycamore trees stand like faithful old sentries in the middle of a quiet block on East Mission Street, near San Jose’s Bernal Park, and at first glance they appear to be identical. Probably planted at the same time, they are about the same size and have a similar wintry grandeur even unadorned by leaves.


But one of these trees is in trouble- as are many trees in San Jose’s urban forest. This one could someday become a danger to the neighborhood, and to Christian Bonner, an arborist at San Jose nonprofit Our City Forest, the difference could not be more obvious. One of the trees has been “topped,” a now discredited method of pruning that has opened the tree to decay, and possible ruin. Bonner suspects the tree’s owner isn’t even aware that it’s in peril.
“People see large canopy trees and they think it’s a potential hazard,” Bonner said. “Then somebody knocks on their door and says, ‘I can prune your tree and make it smaller.’ But when they make those large pruning cuts, they’re actually making the tree less safe.”
The Mercury News asked Bonner, an arborist for nine years, to survey several San Jose neighborhoods to gauge the health of San Jose’s urban forest after a 10-ton silver maple last month suddenly toppled on a pickup truck killing 2-year-old Mateo Ortiz. Mateo’s death- and the debate in its aftermath over who is responsible for San Jose’s street trees – has raised questions about the safety of the trees planted decades ago along the city’s sidewalks.
“It’s not natural to have as many problems as you see around San Jose,” said Rhonda Berry, CEO of Our City Forest, which plants many of the trees in San Jose. “We have a very neglected urban forest.”
The city’s Department of Transportation is considering a proposal to tax homeowners for the upkeep of street trees. But for now, homeowners are responsible.
Bonner was asked to discuss problems homeowners might encounter and to suggest ways to get San Jose’s wooded parking strips thriving again. Hiring professionals doesn’t always produce a better result. “There are many unscrupulous landscapers, and some unscrupulous arborists, as well,” Bonner said. “If you have an arborist come out to do an assessment on the trees at your home, I’d be willing to wager that nine out of 10 would say, ‘Prune your tree,’ regardless of whether it’s needed or not. They’re businessmen and they’re trying to make a buck.”
Rooting out problems
Tree people like to refer to it as the “urban forest,” a slightly dramatic name for a lush landscape of fruit trees radically changed by development in San Jose over the past century. Willow trees no longer line the streets of Willow Glen, and oak trees have become scarce in Oak Grove. What’s left is a stand of street trees in a concrete jungle “filled with subdivisions and malls that are named after the trees that were cut down to build them,” Bonner said.
The most visible swath of any urban forest is its street trees. They float next to parked cars and give shade to kids riding skateboards. A small fraction of the urban forest is planted in grass strips usually no more than 3 or 4 feet wide.
Bonner found an array of bad choices that had been made about the types of trees planted in those fateful park strips. And he pointed out many “missed opportunities” by the city to improve the health of its estimated 242,000 curbside trees. And though he never criticized City Arborist Ralph Mize, Bonner noted the futility of the office as it’s currently constituted. “The city arborist’s office doesn’t have the resources it needs to enforce what’s on the code,” he said. “There’s all kinds of illegal removal, topping and pruning that’s done that they can’t even begin to look at because they have two inspectors for the entire city.”
Every neighborhood is dominated by different types of trees, each with their own advantages and challenges. Bonner’s tour took in only a small percentage of the city’s treescape, which means he also only rooted out a few of the problems homeowners confront. Cruising down the 300 block of Gifford Avenue, Bonner spotted a sycamore- the second-most often planted tree in San Jose, after the Chinese Pistache- whose branches had been crudely shorn, and its canopy “topped.” That technique of removing large branches within the canopy of a tree was a prominent feature of the Yellow Pages advertising of virtually every tree service company in Silicon Valley as recently as a decade ago. Now certified arborists conform to a nationwide pruning standard that forbids topping.
But that hasn’t stopped determined homeowners from firing up their chain saws, trying to maintain the 14-foot vertical clearance above the street mandated by city ordinance. “It costs a couple of hundred dollars to hire a tree care company, so they do what they can, and that’s what they can reach when they get on a ladder,” said Bonner, pointing to a huge gap in the branches that was undermining the structural stability of the tree.
Mushrooming decay
Homeowners sometimes mistakenly assume their large canopy trees are at risk to topple. But trimming them back assures there will be problems. “When they make those large pruning cuts, they’re actually making the tree less safe,” Bonner said. He found an obvious example of this on East Mission Street, where a topped sycamore had opened wounds in its bark, opening the tree to decay. Mushrooms were sprouting from the grass above the roots. “Those mushrooms are a clear indicator that extensive decay exists within the trunk of the tree, and probably in the roots themselves,” he said. “If they had left the tree alone, it would have been fine with a five- or 10-year pruning cycle, and it would have cost them a lot less money.”
The Rose Garden and Willow Glen, among the city’s highest median-income neighborhoods, also have the most mature tree canopies. That’s no accident. “The nicer neighborhoods have really nice trees,” Bonner said. “There’s a direct correlation, and it’s been proven that a house on a tree-lined street is worth more than the same-size house on a street where there are no trees.”
There were other cases of “weed whipper blight,” where exposed tree roots had been damaged by lawn crews. And at one point, a large branch appeared ready to fall on Bonner’s head as he stood in a park strip next to his car. “That’s definitely an imminent hazard,” he said. “If that thing came down on your car, it would probably take the windshield out.” And with that, he put the key in the ignition and quickly drove away.
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In the Urban Forest of San Jose there are many street trees, many problems