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.
Leaving them on the ground made it difficult to tell who had been pulled and who hadn’t