Potamogeton zosteriformis
Eel-grass pondweed
(c) aarongunnar, some rights reserved (CC BY), uploaded by aarongunnar · licence
Family: Potamogetonaceae · Type: Herb · Native
Conservation status: CNPS 2B.2
Potamogeton zosteriformis (Eel-grass pondweed) is a native California herb in the Potamogetonaceae family, recognized by flattened winged stems and many-veined rigid leaves distinctive.
Eel-grass pondweed is a California native annual aquatic plant found in southern North Coast Interior Ranges including Clear Lake, the Great Valley, and Mountain Provinces in ponds, lakes, and streams at elevations below 1,300 meters. Flowering from June to July, this plant produces small, inconspicuous flowers in compact inflorescences less than 3 centimeters long. Growing with compressed, winged stems up to 60 centimeters tall and rarely 4 millimeters wide, it spreads through few branches and winter buds. Its submerged leaves are linear, rigid, 5 to 20 centimeters long and 2 to 5 millimeters wide, with 15 to 35 fine veins and an obtuse to abruptly pointed tip. The fruit is approximately 5 millimeters long with a single prominent keel and convex sides.
Identification and appearance
Key characters: 14 sympatric species; flattened winged stems and many-veined rigid leaves distinctive
Habitat and range
Habitat: Ponds, lakes, streams
Elevation: < 1300 m
Outside California: to British Columbia, eastern North America
Bloom period
Potamogeton zosteriformis blooms Jun-Jul.
Conservation status
CNPS 2B.2
How to tell it apart
vs Persicaria: Potamogeton flowers float on water; Persicaria has terrestrial pink/white flower spikes above solid ground.; vs Stuckenia: Potamogeton flowers emerge above water on stiff stalks; Stuckenia flowers stay underwater on flexible stalks.; vs Alisma: Potamogeton has inconspicuous spike flowers; Alisma has showy white three-petaled flowers in branched clusters.; vs Ranunculus: Potamogeton has tiny greenish spike flowers; Ranunculus has bright yellow buttercup flowers with visible petals.; vs Myriophyllum: Potamogeton has broad or ribbon-like leaves; Myriophyllum has feathery, finely divided leaves like a bottlebrush.
Frequently asked questions
Is Potamogeton zosteriformis native to California?
Yes. Potamogeton zosteriformis is native to California (recorded as native).
When does Potamogeton zosteriformis bloom?
Potamogeton zosteriformis blooms Jun-Jul.
What plant family does Potamogeton zosteriformis belong to?
Potamogeton zosteriformis is in the Potamogetonaceae family, genus Potamogeton.
Is Potamogeton zosteriformis rare or endangered?
Potamogeton zosteriformis carries California Rare Plant Rank 2B.2, state rank S3.
What habitat does Potamogeton zosteriformis grow in?
Potamogeton zosteriformis grows in Ponds, lakes, streams.
Related species
Other California species in the same genus, family, or bioregion.
- Potamogeton alpinus — Alpine pondweed
- Potamogeton amplifolius — Broad-leaved pondweed
- Potamogeton berchtoldii — Narrow leaved pondweed
- Potamogeton crispus — Crisp-leaved pondweed
- Potamogeton diversifolius — Diverse-leaved pondweed
- Potamogeton epihydrus — Nuttall's ribbon-leaved pondweed
- Potamogetonaceae sp. — Pondweed family
- Stuckenia filiformis subsp. alpina — Slender-leaved pondweed
- Stuckenia pectinata — Fennel-leaf pondweed
- Stuckenia sp. — Pondweed
Sources: Jepson eFlora · CalPhotos · CDFW CNDDB
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.