Polygonum aviculare subsp. depressum
Photo by Chez Brungraber
Family: Polygonaceae · Type: Perennial · Not Native
Polygonum aviculare subsp. depressum is a non-native California perennial in the Polygonaceae family.
Prostrate knotweed is a naturalized annual herb found in disturbed places throughout California at elevations below 2,000 meters. Flowering from May to November, this plant produces small greenish or red-brown flowers with white margins, clustered in dense groups of 2 to 7 blooms. Growing as a low, spreading mat with numerous branches, it forms prostrate stems 10 to 50 centimeters long that creep along the ground. Its leaves are elliptic to narrowly elliptic, 8 to 27 millimeters long and 2 to 7 millimeters wide, with obtuse or acute tips and a longitudinal striped texture. The dark brown fruit is slightly exserted, triangular, and typically 1.5 to 2.7 millimeters long with a striate-tubercled surface.
Habitat and range
Habitat: Disturbed places
Elevation: < 2000 m
California counties: Alpine, San Diego, Santa Barbara, Ventura, Los Angeles, Monterey, San Francisco, Kern, Inyo, San Bernardino, Marin, Alameda, Contra Costa, Fresno, Mendocino, Nevada, Stanislaus, Tehama, Trinity, Tuolumne, Butte, Lake, Mariposa, Plumas, San Luis Obispo, San Mateo, Santa Clara, Santa Cruz, Shasta, Siskiyou, Sonoma, Tulare, Yolo, El Dorado, Lassen, Humboldt, Napa, Mono, Riverside, Modoc, Solano, Placer, Imperial, Sacramento, Merced, Sierra, Amador, Yuba, Sutter, Madera, San Joaquin
Outside California: worldwide
Bloom period
Polygonum aviculare subsp. depressum blooms May-Nov.
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 aviculare subsp. depressum native to California?
No. Polygonum aviculare subsp. depressum is not native to California (recorded as not native).
When does Polygonum aviculare subsp. depressum bloom?
Polygonum aviculare subsp. depressum blooms May-Nov.
Where in California does Polygonum aviculare subsp. depressum grow?
Polygonum aviculare subsp. depressum occurs in Alpine, San Diego, Santa Barbara, Ventura, Los Angeles, Monterey, San Francisco, Kern and other counties, at elevations of < 2000 m.
What plant family does Polygonum aviculare subsp. depressum belong to?
Polygonum aviculare subsp. depressum is in the Polygonaceae family, genus Polygonum.
What habitat does Polygonum aviculare subsp. depressum grow in?
Polygonum aviculare subsp. depressum grows in Disturbed places.
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.