Zostera japonica
Dwarf eelgrass
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Family: Zosteraceae · Type: Herb · Not Native
Conservation status: Cal-IPC Yes
Zostera japonica (Dwarf eelgrass) is a non-native California herb in the Zosteraceae family, recognized by leaf width, depth, and sheath structure.
Dwarf eelgrass is a naturalized perennial herb found in northern California coastal areas, occurring in shallow bays and estuaries rooted generally 0 to 1 meters below mean low tide. Flowering from April to August, this marine plant produces small, inconspicuous flowers within its slender green leaves. Growing with thin, ribbon-like leaves up to 20 centimeters long and 1 to 2 millimeters wide, it develops two roots at each node along its underwater stems. Its leaf sheaths are distinctive, featuring open structures with two delicate membranous flaps that help distinguish it from native eelgrass species. This non-native aquatic plant has adapted efficiently to marine environments, spreading through its ability to root and grow in shallow coastal waters.
Identification and appearance
Key characters: 2 sympatric species; key features are leaf width, depth, and sheath structure
Habitat and range
Habitat: Occ. Shallow water, bays, estuaries
Elevation: rooted generally 0-1 m below mean low tide
Outside California: to British Columbia, native to Pacific Asia
Bloom period
Zostera japonica blooms Apr-Aug.
Conservation status
Cal-IPC Yes
How to tell it apart
vs Phyllospadix: Zostera grows in calm bay mud/sand; Phyllospadix grows on wave-swept rocks.; vs Vallisneria: Zostera is marine in saltwater bays; Vallisneria is freshwater in lakes/streams.; vs Ulva: Zostera has narrow ribbon leaves; Ulva is broad sheet-like or lettuce-like green algae.
Frequently asked questions
Is Zostera japonica native to California?
No. Zostera japonica is not native to California (recorded as not native).
When does Zostera japonica bloom?
Zostera japonica blooms Apr-Aug.
What plant family does Zostera japonica belong to?
Zostera japonica is in the Zosteraceae family, genus Zostera.
Is Zostera japonica invasive in California?
Zostera japonica is listed by Cal-IPC with an invasiveness rating of Yes.
What habitat does Zostera japonica grow in?
Zostera japonica grows in Occ. Shallow water, bays, estuaries.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.