for the Trees

written by
Mohammed Nuru

Since San Francisco resumed
responsibility for street trees, the city is well on its way to reaching maintenance goals. The next step—according to
Director of Public Works Mohammed Nuru—is planting more trees.

It was just a few years ago that the fourth-floor City Hall hearing rooms were packed every month with angry property owners, miffed after getting a notice from San Francisco Public Works that the street tree in front of their buildings now would be their responsibility to maintain—no longer the city’s—handing them a financial burden they never wanted.

They showed up at public hearings to appeal the notices, but rarely were their protests upheld. At the end of the day, Public Works did not have the resources to properly care for San Francisco’s 125,000-plus street trees, nor fix the sidewalk damage caused by tree roots.

The city’s last-resort relinquishment policy was a hail-Mary attempt to give the trees a fighting chance: if Public Works couldn’t take care of the trees, hopefully the adjacent property owners could.

Ideally, trees should be pruned every three to five years, depending on the species. Instead, they were put on a 10- to 12-year pruning schedule because the hard-pressed crew of arborists, reduced in size due to budget cuts over the years, didn’t have the staffing resources to do better. They were forced to spend most of their time responding to emergencies, giving routine tree maintenance short shrift. As a result, the health of San Francisco’s urban forest began to decline, creating a stigma for a city that takes great pride in its green credentials.

But given the myriad benefits of trees—among them sequestering carbon emissions to fight global warming, absorbing rainwater to reduce localized flooding, providing habitat for birds and butterflies and beautifying neighborhoods—we knew we had to do something.

In partnership with Friends of the Urban Forest and then-Supervisor Scott Wiener, Public Works began to build the case for the need for a sustainable funding stream to take care of the street trees.

What that should look like, however, took time to develop. First, the Planning Department led efforts to craft San Francisco’s Urban Forest Plan, a well-researched, data-packed document that laid out in stark terms the precarious state of San Francisco’s street tree population largely caused by insufficient funding to care for them. It showcased proven best practices to protect, maintain and manage the urban forest and decisively concluded that steady funding was key.

While the plan detailed how to have a thriving tree population in San Francisco, Friends of the Urban Forest and Wiener went to work building political support to secure the needed funding. Polling, focus groups, and a lot of people-to-people outreach took place, as advocates tried to figure out how best to secure funding for proper tree maintenance over the long term.

A number of financing tools were considered, including a special assessment district, a parcel tax and general obligation bonds. In the end, consensus was reached at City Hall to put before voters in 2016 a proposal to set-aside $19 million a year from the General Fund to pay for tree maintenance and sidewalk repairs to fix damage caused by trees. The big selling point: taxes would not be raised to pay for the services. Voters gave overwhelmingly support, with 79 percent in favor.

With that, StreetTreeSF was born. The program, which effectively quadrupled the Public Works’s tree maintenance and sidewalk repair budget, took effect on
July 1, 2017. 

Passage of the ballot measure was San Francisco voters’ Loraxian moment. “I am the Lorax,” Dr. Seuss wrote in his book, The Lorax. “I speak for the trees, I speak for the trees for the trees have no tongues.”

The ballot-box decision gave Public Works full responsibility for street tree maintenance and tree-related sidewalk damage in the public right of way.

No longer do private property owners have to bear the associated costs of taking care of the trees fronting their apartment buildings, homes and businesses; they don’t have to worry about the liability of tree-related trip and falls or pay for associated sidewalk repairs; and they won’t be hit with hefty fines for improper pruning if they let the city’s professional tree-care crews get the job done the right way.

A major benefit of StreetTreeSF is that, barring an economic catastrophe, funding for proper street tree care is guaranteed year after year—not subject to the uncertainties that come with shifting budget priorities at City Hall.

Now, nearly two years into the program, I can report that a lot of good work has been done. Consider that:

  • More than 33,000 street trees, or roughly 37% of the population, have been pruned.
  • Some 3,000 dead, diseased and dangerous street trees have been removed, including many ficus trees that have posed dangers to people and property.
  • Approximately 1,000 street trees are inspected each month.
  • More than 280,000 square feet of hazardous sidewalk has been removed and replaced and made safe.
  • More than 9,000 tree-related tripping hazards have been abated by fixing the existing sidewalk concrete.
  • StreetTreeSF staff attended nearly a dozen community meetings to let people know about the program.


One of the big challenges we face is building public understanding as StreetTreeSF continues to roll out. When will my tree be pruned? is a frequent question we get.

Our work is informed by a StreetTreeSF census we have with details on every tree: species, location and condition. San Francisco boasts more than 600 species of trees, with the London planetree most prevalent, followed by the Indian laurel fig and the New Zealand Christmas tree.

With that information, we were able to prioritize needs and created a pruning schedule (organized by city blocks and not individual trees). This is the most efficient and cost-effective system that minimizes disruptions to a neighborhood.

We knew from the start that we would prioritize the “worst first”—trees and sidewalks that pose a safety risk and are located near bus stops, schools and senior centers where there’s a lot of foot traffic.

As we’re still playing catch up after years of deferred maintenance, we figure it will be another two to three years before we get into the desired routine pruning cycle. We have an online pruning map that serves as a guide to when and where current work is happening and where it is planned over the next several years. You can plug in your address and get a rough estimate of when the trees on your block will be pruned. The map and other information on StreetTreeSF can be found at

Our crews will quickly pivot from the scheduled work plan to deal with urgent needs: damaged or dead limbs; fallen trees or limbs that block streets, sidewalks and bike lanes; those that block visibility of stop signs and traffic lights or other risks. Public safety is the city’s number one priority.

San Franciscans who want to care for their street trees and not take advantage of the city’s free program are welcome to, as long as they say so in writing and commit to following city pruning standards.

So what’s next for StreetTreeSF? Finding funding to plant trees. The General Fund set-aside and approved by local voters can only be used for maintenance. We want to replace trees we’ve lost to storms and poor condition, and we desire to grow the urban canopy. 

And so do a lot of San Franciscans. While people are no longer livid over the city transferring tree care responsibility to private property owners, there are a lot of folks now who fume to their elected officials that the city isn’t planting more trees. The Board of Supervisors held a hearing on the matter:

San Francisco has one of the smallest tree canopies among major cities in the United States, with just under 14 percent coverage when viewed from above. Compare that to Chicago at 17 percent; New York at 24 percent; and Los Angeles at 21 percent.

The Urban Forest Plan calls for planting 2,500 new street trees a year to get us to a total of 155,000 by 2034. The $19 million annual allocation for StreetTreeSF takes that expansion into consideration when looking at future maintenance costs. But adding more trees to our cityscape takes money. Planting a typical street costs around $500. The three-year establishment period, when regular watering is required to keep it healthy and strong, can add another $1,500 to the cost.

The cost to reach the city’s tree-planting goal would run approximately $12 million, given that about 4 percent of the street trees die naturally in San Francisco every year.

The Public Works Bureau of Urban Forestry and Friends of the Urban Forest are researching options and talking to residents, property owners, elected officials and others about potential funding so we not only make sure our street trees are cared for and thriving but also so San Francisco can boast of having one of the most robust urban forests in the nation.

Mohammed Nuru is director of San Francisco Public Works, the municipal agency in San Francisco that runs the StreetTreeSF program.