Polygonum aviculare subsp. buxiforme
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Family: Polygonaceae · Type: Annual · Not Native
Polygonum aviculare subsp. buxiforme is a non-native California annual in the Polygonaceae family.
Knotweed is a naturalized annual found in California in disturbed places, nondrifting sands, borders of marshes, and dunes at elevations below 3,000 meters. Flowering from July to November, this plant produces small green flowers with white margins in tight clusters. Growing with prostrate to ascending stems that form dense mats 20 to 70 centimeters long, it has multiple branching stems that spread across the ground. Its leaves are lanceolate to elliptic, 6 to 30 millimeters long, with distinctive silvery ocreae (stipule-like sheaths) that persist especially on upper stems. The plant produces light-brown to brown fruits that are 2 to 2.8 millimeters long, typically hidden within the flower clusters.
Habitat and range
Habitat: Disturbed places, nondrifting sands, borders of marshes, dunes
Elevation: < 3000 m
Outside California: North America
Bloom period
Polygonum aviculare subsp. buxiforme blooms Jul-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. buxiforme native to California?
No. Polygonum aviculare subsp. buxiforme is not native to California (recorded as not native).
When does Polygonum aviculare subsp. buxiforme bloom?
Polygonum aviculare subsp. buxiforme blooms Jul-Nov.
What plant family does Polygonum aviculare subsp. buxiforme belong to?
Polygonum aviculare subsp. buxiforme is in the Polygonaceae family, genus Polygonum.
What habitat does Polygonum aviculare subsp. buxiforme grow in?
Polygonum aviculare subsp. buxiforme grows in Disturbed places, nondrifting sands, borders of marshes, dunes.
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.