California Sycamores that line our parkways are in danger

NON-NATIVE TREES grace the 200 S. block of Irving Boulevard.

By Adam G. Schiller
Growing up on McCadden Place launched my fascination with our native tree, Platanus racemosa, often called the California sycamore. Though not colorful, the gnarled trunks, white bark and soft leaves of these trees tower over sidewalks of our streets here in the neigborhood with gentle grandeur.
But the California sycamore is increasingly in danger of widespread death due to disease and the genetic hybridization with trees foreign to the region.

Several illnesses pose serious threats. The most pervasive is a fungus caused by an invasive beetle species that harmed a California sycamore in front of my home years ago. Since appearing in the U.S. in the 2010s, the insect has increasingly threatened native sycamores, and therefore the many species that rely on them as well. We treated that fungus, and the tree survived.

The California sycamore is more than a majestic tree. It is a foundational component of the ecosystem that continues to coexist with us after more than a century of development in the Mid-Wilshire area. If we allow it to disappear, so will the creatures that rely on this species and enrich our neighborhoods. In order to preserve this ecosystem, we need to protect the California sycamore. The process starts on our sidewalks.

Genetic issue

Another issue is genetic, as I learned from my mother, a molecular biologist of plants. The dominant genes of other sycamore varieties, such as the London plane, can spread to nearby local trees through airborne pollination to produce variants that lack the critical California sycamore properties local species depend on for survival.

Genetic hybridization becomes relevant locally when considering how sycamores in Mid-Wilshire are replaced. The Hancock Park Home Owners Association is offering to replace sick or dead native sycamores with non-native trees such as jacarandas and elms. This has been encouraged by claims that the California sycamore has high water needs, though its demands are equal to each of these options in the local climate conditions of Los Angeles. If one were to receive approval to plant a California sycamore, the tree that a homeowner might receive could be hybridized such that it would not support the local ecosystem.

Admittedly, there is little residents can do to directly stop the hybridization of the California sycamore beyond raising awareness. This challenge to its survival may be addressed through greater care on the part of the wildlife restoration groups and local government organizations that impact breeding of the species.

But protecting the California sycamores that tower over our streets is an effort that anyone can pursue. Checking for disease symptoms and beetle infestation is the first step. Residents may then enlist treatment for those on parkways adjacent to their properties. Though not inexpensive, it is a worthy investment, in that mature trees contribute to increasing property values; reduce energy costs; and require less water than saplings. The lifespan of California sycamores, upwards of 400 years, provides benefits far into the future. Additionally, saving existing trees avoids the need to plant non-native trees or hybridized sycamores.

Leafy alternatives to stately sycamore can grow, thrive here

By Chronicle staff

Chris Shogren, an environmental horticulture advisor for UC Cooperative Extension, told us the Sycamore is still recovering from the beetle that came about 10 years ago.

“They are looking better, but last year a resurgence of the beetle population occurred. Many of the sycamores are just aging out as they’ve been in the landscape for 60 years or so.”

When asked about what trees he thought would be good for our sidewalk areas, he said it’s a difficult choice because people like big trees with large canopies, but they demand a larger space around them.

“Crape Myrtle, the most common planted tree in parkways right now, is hardy, and has fewer root issues than sycamores.” It’s also smaller, with colorful and long-lasting flowers in summer. Shogren explained, “The coast live oak, a Los Angeles native, needs a big, wide area and doesn’t like to be watered much in the summer (when Angelenos water most).”

Being a native, it follows our normal weather system where it receives most of its water in winter. Casual summer watering nearby for other landscape is not healthy.

Another interesting point Shogren shared: “There is another tree — the native island oak, which comes from the islands off Southern and Baja California” — which Shogren suggested to the city of Santa Monica “to try because it’s a little bit smaller than an oak, and being in a city near the coast with similar moisture, it might fare well.”

In our area, with less moisture, he spoke of the southwest oak; “It’s smaller and has a much less invasive root system. It is commonly seen in Arizona, which does get some summer rain, so it works with the way we tend to water in our landscapes here in Southern California.”
For recommendations in choosing trees and what sort of space they ought to be in, visit Selectree.calpoly.edu.

Category: Real Estate