Polygonum aviculare subsp. aviculare
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Family: Polygonaceae · Type: Annual · Not Native
Polygonum aviculare subsp. aviculare is a non-native California annual in the Polygonaceae family.
Knotweed is a naturalized annual plant found in California in disturbed places, roadsides, and cultivated fields at elevations below 2,000 meters. Flowering from May to November, this plant produces small green flowers with white to red margins. Growing with ascending or erect stems 10 to 75 centimeters tall that have widely spreading basal branches, it forms low-spreading patches in open areas. Its leaves are elliptic to oblanceolate, 18 to 50 millimeters long and 10 to 20 millimeters wide, with acute or obtuse tips. The fruit is dark brown, three-angled, and approximately 3 millimeters long.
Habitat and range
Habitat: Disturbed places, roadsides, cultivated fields
Elevation: < 2000 m
Outside California: worldwide
Bloom period
Polygonum aviculare subsp. aviculare 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. aviculare native to California?
No. Polygonum aviculare subsp. aviculare is not native to California (recorded as not native).
When does Polygonum aviculare subsp. aviculare bloom?
Polygonum aviculare subsp. aviculare blooms May-Nov.
What plant family does Polygonum aviculare subsp. aviculare belong to?
Polygonum aviculare subsp. aviculare is in the Polygonaceae family, genus Polygonum.
What habitat does Polygonum aviculare subsp. aviculare grow in?
Polygonum aviculare subsp. aviculare grows in Disturbed places, roadsides, cultivated fields.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · 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.