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Over the past year, the Eaton Canyon Habitat Care Team has battled several invasive plant species that have taken over portions of the park in the post-fire landscape. One of these is castor bean (Ricinus communis), a highly invasive plant not native to Southern California that has proved particularly difficult to control. It has also become a favorite for volunteers to remove because of its large size and the immediately visible transformation of the landscape once mature plants are gone.

Properly removing castor bean is a surprisingly involved process. All seed heads must first be clipped off and disposed of properly, with care taken to prevent seeds from falling back onto the ground. The plant must then be cut down with a saw before its roots are dug out of the soil. The process requires several tools, including clippers, a saw, and an Extractigator. If the root system is not removed, the plant can resprout and regain much of its former size within weeks. But the biggest mistake many environmental restoration groups make comes later: failing to return after the first heavy rain to pull the seedlings that emerge from seeds already deposited in the soil. Recent outings at Eaton Canyon have shown that these seedlings can outnumber their parent generation by more than 20-to-1. If they are allowed to mature, months of previous work can effectively be undone, with treated areas becoming even more densely covered in castor than they were before.

Following a rare late-summer deluge that dropped nearly 1.00 inch of rain two weeks ago, the Eaton Canyon Habitat Care Team anticipated exactly this problem and returned to target the new generation of seedlings, having no idea how many they would find. The answer was thousands. Across several acres of the canyon, recently cleared areas were suddenly covered in young castor plants. Because the team returned while the seedlings were still small, however, the work moved dramatically faster than during the original removal effort. Areas that had taken weeks to clear when occupied by mature plants could now be covered in a matter of hours.

Well over 5,000 seedlings were pulled from the canyon in just three hours this past Friday morning by roughly 30 volunteers, significantly reducing the species’ ability to reestablish in the treated area and beginning the long process of depleting its seed bank. Additional work in the same areas will be necessary over the coming months and years as remaining seeds continue to germinate, but each successful outing gives native vegetation more time and space to become established. Over time, the group hopes to eradicate castor bean from the Natural Area entirely. Reaching that goal will not come from one enormous cleanup or from brute force, but rather from returning again and again, catching each new generation before it has the opportunity to produce the next one.

 

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.