The deaths of dozens of coral trees along San Vicente Boulevard's median over the past four years have prompted the city to reevaluate its irrigation policies, as a new risk assessment finds most of the corridor's remaining trees are in poor health and at risk of failing within two years.
A risk assessment by arborist Jonathan Flournoy, dated July 1, evaluated 13 South African coral trees between the 100 and 1900 blocks of San Vicente Boulevard. Nine were rated "high" risk, three "moderate" and one "low." All 13 showed poor foliage, trunk decay and significant root damage, according to the report.
The assessment continues a troubling trend for the corridor, which has lost roughly 32 coral trees over the past four years.
Flournoy identified banana moth infestation, likely following drought stress, as a key factor in the trees' decline, noting that coral trees compartmentalize decay poorly, allowing rot to spread quickly once it takes hold.
Some individual cases documented in the report were severe. One tree in the 400 block had 23% dead trunk circumference and a root plate that has been uplifting for at least seven years. A tree in the 700 block had 55% dead trunk circumference. A third tree in the 1700 block showed signs of past structural failure, including a large basal cavity.
Flournoy said removal, rather than pruning, is the only viable option for trees rated high risk, though the city will determine the timing of any removals.
The findings reflect broader strain on Santa Monica's urban forest, which includes about 35,000 public trees. Roughly 42% of those trees are now mature and nearing the end of their expected lifespan, according to the city.
The tree deaths have drawn scrutiny to how the median has been irrigated over the past decade.
Around 2016, the city retrofitted the median's overhead irrigation system, replacing it with bubblers that watered only the trees rather than the surrounding turf. The change came in response to drought regulations at the time that prohibited watering turf in medians. Depending on their size, the mature coral trees were each fitted with six to eight bubblers, and that system has remained in place since.
For the past 10 years, the bubblers have run for 30 minutes twice a week.
City officials said the tree watering system has functioned well over that period, with one recent exception: a section of the median between 7th and 11th streets has gone without power needed to run the irrigation system. The city has ordered a solar-powered controller for that section and plans to install it upon arrival. In the meantime, the city's landscape contractor has been hand-watering the affected trees weekly.
The city is now working to reinstate the median's overhead irrigation system, officials said. In addition to providing supplemental water to the trees, the restored system is intended to help revive the turf in the median.