Ailanthus Control on the East Edge of Arroyo Seco

Los Angeles County is seeking to chemically destroy a grove of invasive Ailanthus altissima located on a steep slope at the Pasadena City limit, specifically between the Gabrieleno Trail and the west end of Mariposa Street in Altadena, California. This project aims to eradicate a state-recognized noxious weed to protect the native plant community and improve the area for the public. Because the grove is not situated near sensitive species or natural water sources and has not had previous control work, it is a prime candidate for this eradication effort to prevent indefinite expansion. The project is currently listed as a forecast with a posted date of September 2, 2026. Following the initial chemical destruction, the site will be subject to continuous monitoring for several years to ensure the weed does not return. Primary coordination for this effort is managed by Geoff Burch, the Deputy Agricultural Commissioner for Los Angeles County.