Phalaris aquatica
Harding grass, Harding Grass
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Family: Poaceae · Type: Grass · Not Native
Conservation status: Cal-IPC Yes
Phalaris aquatica (Harding grass) is a non-native California grass in the Poaceae family, recognized by large size, swollen stem base, and perennial habit.
Harding grass is a naturalized perennial grass found in northwestern California, the Cascade Range, northern Sierra Nevada, Sacramento Valley, San Francisco Bay Area, southern coastal ranges, southern California, Transverse Ranges, Peninsular Ranges, and Mojave Desert in disturbed areas and roadsides at elevations below 1,700 meters. Flowering from April to August, this grass produces pale green to white flowers in dense, cylindrical clusters 1.5 to 15 centimeters long. Growing in dense, rhizomatous clumps with stems 40 to 200 centimeters tall and swollen at the base, it forms robust, spreading clusters. Its leaves are long and flat, typical of grass species, with characteristic broad blades emerging from the dense, clustered base. The plant occasionally produces bulblets, adding to its ability to spread and colonize disturbed landscapes.
Identification and appearance
Key characters: 10 sympatric species; key features are large size, swollen stem base, and perennial habit
Habitat and range
Habitat: Disturbed areas, roadsides
Elevation: < 1700 m
California counties: Los Angeles, San Bernardino, Mendocino, Humboldt, Santa Barbara, Santa Clara, Orange, Riverside, San Mateo, San Diego, San Francisco, Contra Costa, Ventura, San Luis Obispo, Marin, Napa, Tuolumne, Sonoma, Colusa, Nevada, Calaveras, El Dorado, Fresno, Lake, Solano, Sutter, Tulare, Alameda, Kern, Monterey, Imperial, Trinity, Butte, Yuba, Glenn, Tehama, Sacramento, Shasta, Yolo, Amador, San Joaquin, Santa Cruz, Placer
Outside California: to Oregon, Montana, native to Mediterranean Europe, introduced Africa, America, Australia
Bloom period
Phalaris aquatica blooms Apr-Aug.
Conservation status
Cal-IPC Yes
How to tell it apart
vs Phleum: Phalaris has an ovate to oblong spike-like panicle with keeled, often winged glumes; timothy is a slender cylindric spike with short-awned, stiffly ciliate-keeled glumes.; vs Alopecurus: Phalaris glumes are free and winged and the shiny fertile lemma is flanked by tiny sterile scales; foxtail has glumes joined at the base and a single awned lemma.; vs Anthoxanthum: Both are spike-like, but sweet vernalgrass smells of coumarin and has two awned sterile lemmas; Phalaris is scentless with reduced scale-like sterile florets.; vs Setaria: Phalaris spikes lack bristles entirely; bristlegrass spikelets are each subtended by persistent bristles.; vs Beckmannia: Phalaris spikelets carry prominent winged glumes; sloughgrass has small round, laterally flattened spikelets crowded on one-sided spikes.
Frequently asked questions
Is Phalaris aquatica native to California?
No. Phalaris aquatica is not native to California (recorded as not native).
When does Phalaris aquatica bloom?
Phalaris aquatica blooms Apr-Aug.
Where in California does Phalaris aquatica grow?
Phalaris aquatica occurs in Los Angeles, San Bernardino, Mendocino, Humboldt, Santa Barbara, Santa Clara, Orange, Riverside and other counties, at elevations of < 1700 m.
What plant family does Phalaris aquatica belong to?
Phalaris aquatica is in the Poaceae family, genus Phalaris.
Is Phalaris aquatica invasive in California?
Phalaris aquatica is listed by Cal-IPC with an invasiveness rating of Yes.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-08
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.