The post-fire landscape at Eaton Canyon has brought about a period of change as dramatic as the fire itself. Following the February 2025 flood, the canyon became prime habitat for invasive plant species not native to North America to take over. Although castor bean, short-pod mustard, and tree tobacco often top the list of what comes to mind, County staff and volunteers have also been watching for several other highly invasive species that pose significant long-term ecological threats.
Throughout California, invasive plant species such as Arundo cane, Spanish broom, tamarisk, and Russian thistle have become major ecological problems. At San Gabriel River Park, another Los Angeles County Natural Area acquired and opened to the public in 2024, park staff inherited a well-established infestation of Russian thistle that has proven difficult to control. A quick drive along Highway 126 between Ventura and Santa Clarita reveals the heartbreaking encroachment of Arundo cane in the Santa Clarita Riverbed.
Fortunately, these species have never become firmly established in Eaton Canyon. The exact reason remains unclear, but it may be the result of several factors, including decades without heavy construction equipment capable of spreading seeds, the constant presence of watchdog volunteer naturalists and other regular visitors who quickly dispatch new infestations, and simply the amount of time required for invasive species to gain a foothold.
The fire and flood, however, fundamentally changed those conditions. With the disruption of soil by these natural disasters, these invasive plants have been given the opportunity to establish themselves.
However, the window for those plants to establish themselves has already long ended. Since January 2026, park staff and volunteers have been rigorously dispatching these plants on a weekly, sometimes daily basis. Staff have removed more than 80 individual Arundo cane plants. One plant, which was located below the Pinecrest Gate, required more than 10 hours of labor and the removal of approximately 3 tons of rock and sand (done by shovel) to fully eradicate. Arundo has a rhizome root that must be removed, or else the plant has a 100% chance of regrowing.
In addition, crews have removed 38 newly established tamarisk tree saplings and 12 Russian thistle plants, all before they were able to produce seed. While those numbers may seem small, an unchecked infestation of any one of these species can quickly grow into thousands of plants, making early intervention far less costly than large-scale eradication. No heavy machinery has been required for any of the invasive weed removal.
Although community volunteer events remain within the confines of the County Natural Area portion, staff are doing what they can to get ahead of these species throughout the entire wash ecosystem, and all the way up to the waterfall.
Although castor bean, Maltese star-thistle, tree tobacco, and other invasive grasses remain major ecological challenges in Eaton Canyon, Arundo cane, spanish broom, tamarisk, and Russian thistle are on track to remain absent from that list thanks to the vigilance and early intervention of park staff and volunteers.