Potamogeton illinoensis
Shining pondweed, Shining Pondweed
(c) Samuel A. Schmid, Ph.D., some rights reserved (CC BY), uploaded by Samuel A. Schmid, Ph.D. · licence
Family: Potamogetonaceae · Type: Herb · Native
Potamogeton illinoensis (Shining pondweed) is a native California herb in the Potamogetonaceae family, recognized by paddle-shaped leaves widest near tip with mucro distinctive.
Shining pondweed is a California native perennial found in northern and central California regions including the Cascade Range, Sierra Nevada, Central Valley, Coast Ranges, and Great Basin, inhabiting lakes, ponds, and streams at elevations of 400 to 2,350 meters. Flowering from June to August, this aquatic plant produces small greenish flowers in slender underwater inflorescences less than 6 centimeters long. Growing with multiple branching stems up to 150 centimeters long, it spreads through rhizomes and develops both underwater and floating leaves. Its underwater leaves are elliptic to oblanceolate, 6 to 20 centimeters long with 7 to 19 fine veins, while floating leaves are wider and more rounded, with 13 to 29 veins. The plant produces small fruits 2.5 to 3.6 millimeters long with three distinct keels and a short erect beak.
Identification and appearance
Key characters: 15 sympatric species; paddle-shaped leaves widest near tip with mucro distinctive
Habitat and range
Habitat: Lakes, ponds, streams
Elevation: 400-2350 m
California counties: San Bernardino, Lake, Butte, Los Angeles, Sonoma, Siskiyou, San Francisco, Monterey, Mono, Mendocino, Modoc, Inyo, Alameda, San Mateo, San Diego, San Luis Obispo, Plumas, Santa Clara, Santa Cruz, Yuba, Lassen, Merced, San Joaquin, Stanislaus, Placer
Outside California: to British Columbia, eastern Canada, Texas, Baja California, also Central America, South America, Caribbean
Bloom period
Potamogeton illinoensis blooms Jun-Aug.
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 illinoensis native to California?
Yes. Potamogeton illinoensis is native to California (recorded as native).
When does Potamogeton illinoensis bloom?
Potamogeton illinoensis blooms Jun-Aug.
Where in California does Potamogeton illinoensis grow?
Potamogeton illinoensis occurs in San Bernardino, Lake, Butte, Los Angeles, Sonoma, Siskiyou, San Francisco, Monterey and other counties, at elevations of 400-2350 m.
What plant family does Potamogeton illinoensis belong to?
Potamogeton illinoensis is in the Potamogetonaceae family, genus Potamogeton.
What habitat does Potamogeton illinoensis grow in?
Potamogeton illinoensis grows in Lakes, ponds, streams.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.