For immediate Release — November 27, 2019

Cleaning Up the Arroyo Stream

More than 120 students from Maranatha High School came to the Arroyo Seco in Pasadena this week as part of the Arroyo Seco Foundation's (ASF) Stream Team volunteer program. The two-day event was part of Maranatha's annual Thanksgiving community service program. An energetic crew of students and teachers removed invasive species from the stream just north of the mouth of the Arroyo Seco as it comes out of the San Gabriel Mountains.

The species they hauled out of the canyon included cape ivy, vinca, eupathory, castor bean, tree tobacco and common fig, all non-native species that are categorized as "invasive" because of the way they degrade and dominate the vital native vegetation that provides habitat for fish and wildlife and cleanses the water for local residents. The volunteers removed approximately 400 cubic feet of eupatory (Ageratina adenophora), cape ivy (Delairea odorata), and blue periwinckle (Vinca major) from the stream corridor in the northern portion of Hahamongna Watershed Park. The City of Pasadena Public Works Department provided tools and hauled away the waste.

"This is the third year that Maranatha students and teachers have come to care for the Arroyo stream," said Tim Brick, ASF Managing Director, "and the results of their past efforts are very apparent. Areas that had been overwhelmed in the past by the persistent vines and other weed species were much cleaner and healthier this year." The appropriate native riparian woodland species, including white alder (Alnus rhombifolia), California sycamore (Platanus racemosa), coast live oak (Quercus agrifolia), and holly leaf cherry (Prunus ilicifolia), are recovering . Several seedlings of each sprouted as witnesses to the success of the previous work. During the activity, volunteers also observed two Pacific tree frogs (Pseudacris regilla) and a toe-biter or Giant Water Bug (Family Belostomatidae).

The students also took on a scenic mesa along the nearby trail into the Arroyo on the east from Altadena Drive near Pasadena Water & Power Department's former Behner Treatment Plant. That area is a mix of high quality alluvial sage scrub habitat, such as buckwheat and sagebrush, along with aggressive invasive species such as horehound, mustard, and castor bean. The goal is to make that site a showcase of high quality native habitat.

The habitat restoration and invasive species eradication activity is part of ASF's Stream Team program, a volunteer-based program that includes education and activities aimed at protecting and upgrading the quality of habitat and water conditions along the Arroyo Seco, a major tributary of the Los Angeles River. Restoring precious habitat like these two sites is critical to the long-term success of the program and to the health of the Arroyo Seco Watershed.

If you would like to get involved in the Stream Team, please send an email to


Getting Ready to Work

Piling up the Weeds

Eupatory - One of the Most Prominent Invasives

Cape Ivy - A Persistent Vine in the Streamzone