Polygonum minimum
Broadleaf knotweed
(c) Ken-ichi Ueda, some rights reserved (CC BY), uploaded by Ken-ichi Ueda · licence
Family: Polygonaceae · Type: Herb · Native
Polygonum minimum (Broadleaf knotweed) is a native California herb in the Polygonaceae family, recognized by distinctive broad ovate to round leaves.
Broadleaf knotweed is a California native annual found in northwestern California, the California Cascades, and the Sierra Nevada in meadows and open rocky areas at elevations of 700 to 3,500 meters. Flowering from July to September, this plant produces small white or pink flowers near the stem base and along the branches. Growing with wiry, often zigzagged red-brown stems 2 to 30 centimeters tall that are papillate-scabrous and angular, it spreads in a low, prostrate to erect form. Its leaves are densely clustered, narrowly elliptic to round, 6 to 27 millimeters long with flat margins that are irregularly thickened or finely toothed. The fruit is a small, shiny black elliptic to ovate structure 1.8 to 2.3 millimeters long.
Identification and appearance
Key characters: 26 sympatric species; distinctive broad ovate to round leaves
Habitat and range
Habitat: Meadows, open rocky or +- barren soil
Elevation: 700-3500 m
California counties: Plumas, Tehama, Fresno, Mariposa, Inyo, Siskiyou, Trinity, Tulare, Monterey, El Dorado, Butte, Madera, Mono, Alpine, Humboldt, Nevada, Shasta, Calaveras, Mendocino, Sierra, Glenn, Lassen, Yuba, Placer, Tuolumne, Del Norte, Colusa, Amador, Lake
Outside California: western North America
Bloom period
Polygonum minimum blooms Jul-Sep.
How to tell it apart
vs Euphorbia: Polygonum has swollen stem joints with papery sheaths; Euphorbia has milky sap when broken.; vs Persicaria: Hold node sheaths to light—Polygonum's are translucent and split; Persicaria's are opaque and intact.; vs Eriogonum: Polygonum has papery sheaths at nodes; Eriogonum has flowers in cup-like involucres.; vs Acmispon: Polygonum has swollen stem nodes; Acmispon has compound leaves with 3-5 leaflets.; vs Atriplex: Polygonum has papery stem sheaths; Atriplex has mealy or scurfy coating on leaves.
Frequently asked questions
Is Polygonum minimum native to California?
Yes. Polygonum minimum is native to California (recorded as native).
When does Polygonum minimum bloom?
Polygonum minimum blooms Jul-Sep.
Where in California does Polygonum minimum grow?
Polygonum minimum occurs in Plumas, Tehama, Fresno, Mariposa, Inyo, Siskiyou, Trinity, Tulare and other counties, at elevations of 700-3500 m.
What plant family does Polygonum minimum belong to?
Polygonum minimum is in the Polygonaceae family, genus Polygonum.
What habitat does Polygonum minimum grow in?
Polygonum minimum grows in Meadows, open rocky or +- barren soil.
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.