Limnobium spongia
American frogbit, American Frogbit
(c) Sindupa De Silva, some rights reserved (CC BY) · licence
Family: Hydrocharitaceae · Type: Herb · Not Native
Conservation status: Cal-IPC Yes
Limnobium spongia (American frogbit) is a non-native California herb in the Hydrocharitaceae family, recognized by Southeastern US species naturalized in California; specialized aquatic habitat.
American frogbit is a naturalized aquatic perennial found in northern California coastal and San Francisco Bay bioregions in streams, ponds, and lagoons at elevations below 200 meters. Flowering from June to September, this plant produces white flowers with three petals and three sepals. Growing as a floating aquatic plant with leaves 1 to 10 centimeters long and 0.9 to 7.8 centimeters wide, it spreads through water habitats with petioles up to 15 centimeters long. Its leaves are distinctively ovate to nearly round, with bases that are kidney-shaped or heart-shaped. The plant produces small fruits approximately 4 to 12 millimeters in diameter.
Identification and appearance
Key characters: Southeastern US species naturalized in California; specialized aquatic habitat
Habitat and range
Habitat: Streams, ponds, lagoons
Elevation: < 200 m
Outside California: southeastern United States, northern to New York
Bloom period
Limnobium spongia blooms Jun-Sep.
Conservation status
Cal-IPC Yes
How to tell it apart
vs Pontederia: Limnobium has small round floating leaves; Pontederia has large upright arrow-shaped leaves emerging above water.; vs Najas: Limnobium floats with round leaves; Najas is fully submerged with narrow leaves on branching stems.; vs Hydrilla: Limnobium floats on surface; Hydrilla grows entirely underwater with whorled narrow leaves.; vs Elodea: Limnobium has floating round leaves; Elodea is submerged with whorled narrow leaves on stems.; vs Egeria: Limnobium floats with heart-shaped leaves; Egeria grows submerged with whorled narrow leaves on stems.
Frequently asked questions
Is Limnobium spongia native to California?
No. Limnobium spongia is not native to California (recorded as not native).
When does Limnobium spongia bloom?
Limnobium spongia blooms Jun-Sep.
What plant family does Limnobium spongia belong to?
Limnobium spongia is in the Hydrocharitaceae family, genus Limnobium.
Is Limnobium spongia invasive in California?
Limnobium spongia is listed by Cal-IPC with an invasiveness rating of Yes.
What habitat does Limnobium spongia grow in?
Limnobium spongia grows in Streams, ponds, lagoons.
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.