Persicaria amphibia
Water smartweed
(c) Kevin Krebs, some rights reserved (CC BY), uploaded by Kevin Krebs · licence
Family: Polygonaceae · Type: Perennial · Native
Persicaria amphibia (Water smartweed) is a native California perennial in the Polygonaceae family, recognized by aquatic habitat and showy pink-red flowers are key.
Water smartweed is a California native perennial found in western and central California, excluding the eastern Desert Mountains, growing in shallow lakes, streams, and shores at elevations below 3,000 meters. Flowering from June to November, this plant produces pink to red flowers in terminal clusters 10 to 150 millimeters long. Growing with prostrate to erect stems 20 to 120 centimeters tall that can be glabrous or hairy, it has distinctive rhizomes or stolons. Its leaves are ovate to lance-oblong, 2 to 15 centimeters long with tapered or rounded bases and acute tips, featuring ocrea (leaf-like sheaths) 5 to 50 millimeters long in tan to dark-brown colors. The fruit is a small, lens-shaped, dark-brown structure 2 to 3 millimeters long.
Identification and appearance
Key characters: 8 sympatric species; aquatic habitat and showy pink-red flowers are key
Habitat and range
Habitat: Shallow lakes, streams, shores
Elevation: < 3000 m
California counties: San Diego, San Bernardino, Glenn, Lake, Modoc, Sonoma, Butte, Calaveras, Del Norte, Inyo, Kings, Lassen, Madera, Orange, Riverside, Solano, Stanislaus, Mendocino, Napa, Siskiyou, Ventura, Contra Costa, El Dorado, Humboldt, Kern, Marin, Merced, Monterey, Nevada, Plumas, San Francisco, San Joaquin, San Luis Obispo, San Mateo, Santa Barbara, Santa Clara, Santa Cruz, Shasta, Tulare, Tuolumne, Yolo, Tehama, Mono, Colusa, Sierra, Placer, Sacramento, Alpine, Fresno, Sutter
Outside California: northern hemisphere, naturalized in South America, southern Africa
Bloom period
Persicaria amphibia blooms Jun-Nov.
How to tell it apart
vs Polygonum: Persicaria has opaque stem sheaths; Polygonum has translucent sheaths that split into two lobes.; vs Rumex: Persicaria has spike-like pink/white flower clusters; Rumex has branched greenish flower clusters.; vs Trifolium: Persicaria has spike/head flower clusters and papery stem sheaths; Trifolium has clover heads and no sheaths.; vs Salix: Persicaria is an herb with flower spikes; Salix is a woody shrub with catkins.; vs Phytolacca: Persicaria has small pink/white flowers in spikes; Phytolacca has white-green flowers and dark purple berries.
Frequently asked questions
Is Persicaria amphibia native to California?
Yes. Persicaria amphibia is native to California (recorded as native).
When does Persicaria amphibia bloom?
Persicaria amphibia blooms Jun-Nov.
Where in California does Persicaria amphibia grow?
Persicaria amphibia occurs in San Diego, San Bernardino, Glenn, Lake, Modoc, Sonoma, Butte, Calaveras and other counties, at elevations of < 3000 m.
What plant family does Persicaria amphibia belong to?
Persicaria amphibia is in the Polygonaceae family, genus Persicaria.
What habitat does Persicaria amphibia grow in?
Persicaria amphibia grows in Shallow lakes, streams, shores.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · 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.