Glyceria ×occidentalis
Western manna grass, Western Manna Grass
Family: Poaceae · Type: Perennial · Not Native
Glyceria ×occidentalis (Western manna grass) is a non-native California perennial in the Poaceae family, recognized by hybrid origin, distinctive floating habit and appressed spikelets.
Western manna grass is a naturalized perennial herb found in northwestern California, northern Sierra Nevada, Sacramento Valley, central Coast, and San Francisco Bay Area in freshwater marshes, ponds, and streams at elevations below 1,300 meters. Flowering from June to August, this grass produces small spikelets in narrow inflorescences 15 to 40 centimeters long. Growing 70 to 150 centimeters tall with stems 1.5 to 2 millimeters in diameter, it often forms floating mats in aquatic environments. Its leaves feature ligules 5 to 12 millimeters long and blades 20 to 30 centimeters in length, typically 4 to 13 millimeters wide. Each spikelet contains 6 to 13 florets with lemmas 4.5 to 6 millimeters long, whose tips can be entire, dentate, or crenate.
Identification and appearance
Key characters: 7 sympatric species; hybrid origin, distinctive floating habit and appressed spikelets
Habitat and range
Habitat: Freshwater marshes, ponds and streams
Elevation: < 1300 m
Outside California: British Columbia, Idaho
Bloom period
Glyceria ×occidentalis blooms Jun-Aug.
How to tell it apart
vs Pleuropogon: Glyceria has closed leaf sheaths and 1-veined upper glumes; Pleuropogon has open sheaths and distinctive bumpy, jointed spikelet axes.; vs Oloptum: Glyceria has closed sheaths in wetlands; Oloptum has open sheaths in dry sites with needle-like rolled leaves.; vs Torreyochloa: Glyceria has 1-veined upper glumes; Torreyochloa has 3-veined upper glumes and more prominent lemma veining.; vs Puccinellia: Glyceria has closed leaf sheaths in freshwater; Puccinellia has open sheaths in saline/alkaline sites.; vs Desmazeria: Glyceria is perennial in wetlands with closed sheaths; Desmazeria is annual of dry sites with open sheaths.
Frequently asked questions
Is Glyceria ×occidentalis native to California?
No. Glyceria ×occidentalis is not native to California (recorded as not native).
When does Glyceria ×occidentalis bloom?
Glyceria ×occidentalis blooms Jun-Aug.
What plant family does Glyceria ×occidentalis belong to?
Glyceria ×occidentalis is in the Poaceae family, genus Glyceria.
What habitat does Glyceria ×occidentalis grow in?
Glyceria ×occidentalis grows in Freshwater marshes, ponds and streams.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CalPhotos
Last updated 2026-09-30
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.