California Invasive Plant Council

Phalaris aquatica

Synonyms: Phalaris commutata, Phalaris stenoptera, Phalaris tuberosa

Common names: harding grass; bulbous canarygrass; phalaris; toowoomba grass

Phalaris aquatica (harding grass) is a perennial grass (family Poaceae) found throughout California. Harding grass is widespread in California because it has been used as a forage species and for revegetating after fires. It is most common in coastal valley and foothill grasslands from Oregon to the Mexican border. It is also found in the Sacramento and San Joaquin valleys at elevations below 4,000 feet (1,200 m). Harding grass is typically found along roadsides that are seldom mowed, allowing this tall, erect, leafy plant to dominate neighboring vegetation. In wildland habitats, harding grass can out-compete and displace native plant species. Tall stands of its dry foliage can present a fire hazard in summer.

Cal-IPC Rating: Moderate?

Explanation of Cal-IPC ratings

• High – These species have severe ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal and establishment. Most are widely distributed ecologically.
• Moderate – These species have substantial and apparent-but generally not severe-ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal, though establishment is generally dependent upon ecological disturbance. Ecological amplitude and distribution may range from limited to widespread.
• Limited – These species are invasive but their ecological impacts are minor on a statewide level or there was not enough information to justify a higher score. Their reproductive biology and other attributes result in low to moderate rates of invasiveness. Ecological amplitude and distribution are generally limited, but these species may be locally persistent and problematic.
• Alert – An Alert is listed on species with High or Moderate impacts that have limited distribution in California, but may have the potential to spread much further.
• Watch – These species have been assessed as posing a high risk of becoming invasive in the future in California.

CDFA Rating: None?

Explanation of CDFA ratings

• A – A pest of known economic or environmental detriment and is either not known to be established in California or it is present in a limited distribution that allows for the possibility of eradication or successful containment.
• B – A pest of known economic or environmental detriment and, if present in California, it is of limited distribution.
• C – A pest of known economic or environmental detriment and, if present in California, it is usually widespread.
• D – An organism known to be of little or no economic or environmental detriment, to have an extremely low likelihood of weediness, or is known to be a parasite or predator.
• Q – An organism or disorder suspected to be of economic or environmental detriment, but whose status is uncertain because of incomplete identification or inadequate information.
• * – An asterisk next to the rating indicates that a plant is included in the CCR Section 4500 list of California State Noxious Weeds.
• -* – This plant is included in the CCR Section 4500 list of California State Noxious Weeds, but is otherwise not rated.

More details

Assessment(s)

Phalaris aquatica Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.

Weed Management Notes

• Management Notes - Information on management techniques and effectiveness from the University of California Cooperative Extension’s Weed Research & Information Center.

Cal-IPC Newsletter Articles

• Prescribed grazing for invasive plant control on rangelands. Davy, Josh; Tate, Kenneth; Roche, Leslie. Vol 21, Issue 3

Cal-IPC Symposium Presentations

Presentations are linked where available. Where a presentation is not available, find more information by reading the abstract in the Cal-IPC Symposia Archive.

• Riding the invasion curve: Invasive plant management on Santa Catalina Island. Kreisberg, Aaron (2024)
• Control of invasive plants after the Scorpion Fire on Santa Cruz Island. Woolsey, Jay; Parker, Mike; Carter, Katy; Little, Annie; Cowan, Clark (2022)
• Two years after the fire: accomplishments in invasive plant control following the 2018 Woolsey Fire. Algiers, Joey (2020)
• Weeds after Woolsey. Algiers, Joseph (2019)
• Controlling Harding grass (Phalaris aquatica) in a grassland setting _ an interim report. Samuels, Stassia; Julian, Laura S. (2012)
• Control of Phalaris aquatica on lowland coastal terrace prairie in Richmond, CA. Stafford, Monica; Farrell, Sharon; Beyer, Claire (2006)
• Grasses working group. Clines, Joanna; DiTomaso, Joe; Meyer, Tanya (2004)
• Out of the frying pan: Invasion of exotic perennial grasses in coastal prairies. Corbin, Jeffrey D.; Thomsen, Meredith; Alexander, Janice; D_Antonio, Carla M. (2004)
• Annual grasses: Status of biology and control. D'Antonio, Carla; Gerlach, John (2003)

Other Phalaris aquatica Information

• Bugwood - National database from the Center for Invasive Species and Ecosystem Health at the University of Georgia.
• CalPhotos - Images of plants taken mostly in California.
• Calflora - Distribution map and records of this species in California.
• CalWeedMapper - Distribution map of this species in California with ability to determine regional priorities.
• EDDMapS - Distribution of this species in North America.
• Jepson Interchange - Information on this plant's taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
• USDA PLANTS Database - Information on identification and distribution, with links to websites in individual states.

Additional photos