‘It’s a bad weed’: Invasive arundo grass is spotted near La Jolla’s Children’s Pool

A small grouping of invasive, tall arundo grass has been spotted next to Coast Boulevard on a bluff near La Jolla’s Children’s Pool.

Jason Allen, president of San Diego-based Black Sage Environmental, which helped remove arundo grass from the nearby Coast Walk Trail, said the species can grow 20 to 30 feet tall if left unattended in the right conditions.

Arundo originates in Southwest Asia and usually grows in wetland areas, Allen said. “It is considered invasive because it grows quickly and takes a lot of water and can out-compete native vegetation that should grow in that area,” he said. “It’s a bad weed.”

Allen said the plant reproduces through small flowers or portions of the root structure that “break off and aren’t always noticeable” — a process called fragmentation. In such cases, the root structure detaches and flows down a river or another water source, gets stuck in mud and grows from there.

Upon seeing photos shown to him by the La Jolla Light, Allen — who had not seen the site himself — confirmed the plant is arundo but said he didn’t know how the grouping came to be.

Arundo grass is considered invasive because it takes water from native plants.

(Ashley Mackin-Solomon)

Representatives of the city of San Diego did not immediately respond to the Light’s request for comment about the plant or whether it would be removed.

In places where it grows naturally, arundo can be used to slow erosion because “it catches sediment and debris,” Allen said. But in places where it does not grow naturally, “it can grow very heavy, and I would rather see the whole coastal edge be native plants,” he said.

One of the ways to remove it, Allen said, is by digging it out from the root. “There are other ways to kill it, but those ways require follow-up visits,” he said. “Arundo doesn’t die easily.”

The presence of arundo grass in La Jolla isn’t new.

About a dozen years ago, the then-fledgling Friends of Coast Walk Trail formed to remove arundo grass from the trail because it had overgrown native species. Black Sage Environmental removed the arundo in 2011 and worked to replant the space with native species conducive to erosion control.

More recently, as part of an effort to clean up the La Jolla Bike Path, organizer Debbie Adams said removing arundo grass is a priority.

“It’s growing in about four places and spreading like crazy,” Adams said earlier this year. “In our hopes and dreams, we would like to see it gone forever so we can plant some nice trees and native vegetation.” ◆