Pampas Grass Eradicated from Hawai’i Island, BIISC Reports

PC: Big Island Invasive Species Committee

The invasive pampas grass has been uprooted from all known locations on Hawai’i Island.

The Big Island Invasive Species Committee announced the eradication of the grass on Tuesday. Two species of pampas grass occur in Hawai‘i, Cortaderia jubata and Cortaderia selloana; both are on the state’s Noxious Weeds list.

Removal of the plants by BIISC crews took time, as permission from property owners was required for most of the sites, according to a BIISC press release.

“Locating and contacting property owners can pose a significant challenge for control efforts, but overall most homeowners were cooperative and eager to support the removal of an invasive plant from their property,” the release stated.

Hawai‘i Department of Agriculture assisted with securing access for removal where permission was difficult to obtain. When BIISC crews removed the last known plant in 2019, they replanted the area with native mamaki.

Although most of the adult plants were removed early in the eradication timeline, Joel Brunger, the field operations supervisor for BIISC, explains that with a potential seed spread of up to 20 miles, surveying for pampas grass near known locations required a significant investment of time.

“After the adult plants are removed, we have to return and conduct sweeps regularly for new sprouting keiki for as long as the seeds are viable,” Brunger said. “For pampas grass, that’s six years.”

BIISC said pampas grass is still sold throughout the world in the horticultural trade and for landscaping. During the course of the eradication effort, BIISC developed the Plant Pono program, a nursery endorsement and education effort aimed at stopping the sale of invasive plants in Hawai‘i.

Plant Pono-endorsed nurseries voluntarily pledge to sell only non-invasive “pono” plants. There have been no sales of pampas grass in Hawaii for the last several years, although seeds purchased online continue to be a risk for introductions of invasive plants.

“People often look at widespread invasive plants like albizia or clidemia and say, why didn’t anyone do something about it before it became this bad?” asked Franny Brewer, communications director for BIISC. “That’s what we’re trying to do. Identify what has come in that is potentially the next serious problem, and remove it before it has decades to spread.”

Brewer explains that once a harmful species reaches a certain point, complete eradication becomes so expensive — in the tens or even hundreds of millions of dollars — that removal of the species is no longer feasible.

Currently, BIISC is targeting a number of other plants for eradication, including Mollucca raspberry, a thorny, sprawling brush species, and a holly tree that can establish in native forest areas.

As with pampas grass, public reports are a critical tool in efforts to eradicate invasive plants. To learn how to identify and report target species, visit www.biisc.org.