A newly completed risk assessment has found that more than two-thirds of a sample of coral trees in the San Vicente Boulevard median are in poor health and pose a "high" risk of failure within the next two years, adding to a wave of tree losses that has already claimed roughly 32 coral trees along the corridor over the past four years.
The assessment, conducted for the city by arborist Jonathan Flournoy of Jonathan Flournoy Consulting LLC, evaluated 13 South African coral trees (Erythrina caffra) growing in the median between the 100 and 1900 blocks of San Vicente. Nine of the 13 trees were rated "high" risk, three were rated "moderate," and one was rated "low," according to the report, dated July 1 and addressed to Madeleine Rauhe, the city's urban forester.
"All 13 coral trees that I evaluated were in poor condition, with very little or no green foliage on the trees," Flournoy wrote in the report. Most of the trees also had large areas of dead or rotting bark on their lower trunks, and all 13 showed significant root damage or decay, some more advanced than others.
Flournoy, an International Society of Arboriculture board-certified master arborist and a registered consulting arborist, inspected the trees on June 23 and June 30. His report notes that the city had already marked multiple coral trees in the median for removal because of wood decay and poor health before commissioning the broader assessment.
The likely culprit behind the bark damage, Flournoy wrote, is banana moth, an insect that attacks coral trees already under stress. The pest can follow damage from the invasive shot hole borer, though it also attacks stressed coral trees independently. Flournoy said he suspects drought stress is the primary factor weakening the trees but noted that identifying the root cause of the decline was outside the scope of his assignment.
Compounding the problem, Flournoy wrote, is that coral trees are poor at compartmentalizing decay — meaning they struggle to wall off rot once it takes hold — and decay tends to spread rapidly even in otherwise healthy specimens. Healthy coral trees can typically grow new wood fast enough to offset the loss of structural stability, he wrote, but the trees he examined showed little evidence of that kind of recovery.
Given the trees' condition, Flournoy said he does not see viable options short of removal. Reducing a tree's height to ease the load on a decayed trunk and root system, he wrote, would require cuts large enough to constitute topping — a practice that creates its own decay-prone wounds — and would further stress trees already in poor health.
Several individual trees illustrated the severity of the damage. One tree in the 400 block had 23% of its trunk circumference dead on the side that bears the most structural load, along with a root plate that Flournoy said has been slowly uplifting for at least seven years, based on a comparison with 2019 street-level imagery; he also found fruiting bodies from Ganoderma fungus at its base. A tree in the 700 block had roughly 55% of its trunk circumference dead at the base, with most of its anchor roots also dead on the upper surface. A tree in the 1700 block showed evidence of a past trunk failure, with 60% of its trunk circumference dead and a large cavity at the base.
Risk ratings combine the likelihood a tree or tree part will fail, the likelihood it would strike something if it did, and the severity of the consequences. For most of the high-risk trees, Flournoy rated the likelihood of failure as "probable" within two years and found a "high" likelihood that a falling tree or limb would strike a vehicle, given the steady traffic on San Vicente. He rated the combined likelihood of failure and impact as "likely," with "severe" potential consequences — a combination that produced the "high" overall risk rating.
Flournoy said trees near the western end of San Vicente, closer to Ocean Avenue, generally posed less risk to vehicles because of lighter traffic in that stretch. The lowest-rated tree in the assessment, near the 100 block, was found to have significant root damage but retained many intact anchor roots close to the trunk.
The report recommends monitoring the moderate- and low-risk trees at least every six months, warning that their risk ratings could climb to "high" if their condition continues to deteriorate. Flournoy's report does not set a timeline for removal of the high-risk trees; that decision rests with the city as the trees' owner. "The tree owner ultimately decides whether to keep the trees based on their risk tolerance and other factors," Flournoy wrote. "If the tree owner does not accept the risk posed by the trees, then the trees should be removed."
The San Vicente findings arrive against the backdrop of a citywide urban forest that is itself showing signs of strain. Santa Monica's Public Landscape Division, part of the Public Works Department, oversees more than 35,000 public trees across more than 250 species, guided by a 50-year Urban Forest Master Plan adopted in 2011 and updated in 2017. The city has held Tree City USA status for more than 40 years and estimates its street trees provide about $5.1 million a year in ecosystem benefits.
But roughly 42% of the city's public trees are mature and nearing the end of their useful life, according to the city, and the broader region has seen disease and pest pressures similar to what Flournoy documented on San Vicente. The invasive shot hole borer and associated Fusarium dieback complex, first identified in Los Angeles County in 2012, now affects more than 50 hardwood species across seven Southern California counties. City crews have also flagged other trees for removal in recent years due to ganoderma fungal infections and irreversible decline.
Questions about how the city irrigates its street trees and medians remain only partly answered. Back in 2015 officials said Santa Monica had begun hand-watering trees and using slow-release watering bags, while halting irrigation of grassy street medians altogether to conserve water. No information was available at press time as to the current status of watering for the San Vicente trees in specific or the overall city policy on watering trees in the public right of way.