Noe Valley Voice July-August 2008

The Roots of Local Tree Troubles

By Josh Brandt

Even in the halcyon enclave of Noe Valley, where the gentle whir of latte machines blends seamlessly with the rhythmic machinations of baby strollers, there are crimes committed daily. These crimes, while not heinous enough to warrant a ticket or jail time, affect living organisms that provide a vital role in any neighborhood.

The perpetrators are vandals, litterbugs, automobiles, and, most egregiously, canines and aphids. The victims? Trees.

"People do weird things to trees--it's a side of humanity you don't like to see," says Debra Niemann, director of the Noe Valley Association, a community benefit district funded by the city of San Francisco and property owners in "Downtown Noe Valley."

One of the main missions of the NVA is to "clean and green" the 24th Street corridor, a task made more complicated by the street's heavy foot traffic.

"I've seen cross-bars, which were meant to stabilize trees, karate-chopped in half," reports Niemann. "You don't want to think that people who walk down the same streets as you do are capable of doing things like that, but that's the reality."

She's also seen people use the tree wells as their personal trash can, tossing shopping bags, coffee cups, and junk left over from garage sales.

Niemann points out that one of the biggest threats to a young tree's survival is dog urine. The urine coagulates around the tree well, contaminating the soil, she says. The trees outside of Walgreen's have had to be removed twice, both times due to an excess of dog urine, Niemann says.

Certain saplings can't stand the abuse. "There is a tipping point for going green," says Niemann, noting that the NVA's annual budget of $225,000 allows for only so much upkeep and tree replacement.

Sharon Korotkin, of the landscape firm Korotkin Associates, which at the NVA's request has been involved in the maintenance of over 100 trees in Noe Valley since the fall of last year, says there are myriad factors impacting a tree's survival. To increase a tree's chances, she recommends a good pedigree.

"There are certain types of trees that are hardier, like ginkgoes, which have been around as long as cockroaches and crocodiles. They've had a long history of adapting to different conditions in order to survive."

Korotkin says the young gingko trees are outside Starbucks at 24th and Noe streets. The vast majority of the other newly planted trees are kwanzan cherry and callery pear trees, she says.

As for the canine problem, Korotkin says the high salt content in dog urine rests on top of the soil, sucking the moisture out and robbing the tree of its natural irrigation system. For that matter, when a human, dog, or any other mammal tramples on the soil bed surrounding a newly planted tree, the pressure pushes oxygen out of the soil and deprives the roots of important nutrients.

"Animals are territorial," Korotkin noted. "If they urinate in one place, they tend to urinate in it time and time again. Any newly planted tree is going to suffer if dog owners allow their pets to treat trees as toilet bowls. People need to curb their dogs."

And then there are the aphids.

Aphids are disastrous for trees. They feed on twigs, branches, and bark. They also secrete a sweet paste called honeydew, which attracts ants. The ants often act as guardians of aphid eggs, transporting them en masse up tree trunks. To combat the tiny scourges, Korotkin introduces an insect larva which lays eggs inside the bodies of the aphids. When the larva hatches, the insect eats the aphid from the inside out.

"It's kind of gross, but that's the insect world for you," Korotkin says with a laugh.

Although she's seen a few trees felled by neighborhood miscreants of various shapes, sizes, and secretions, Korotkin revels in her job protecting Noe Valley's urban groves.

"There's a wonderful aesthetic component to trees that's very obvious," says Korotkin. "But trees are a life-giving entity that's crucial to our survival as a species, and it's wonderful to be a part of that."