Polygonum fowleri subsp. fowleri
Family: Polygonaceae · Type: Herb · Native
Polygonum fowleri subsp. fowleri is a native California herb in the Polygonaceae family, recognized by maritime habitat, succulent leaves, beaked fruits.
Fowler's knotweed is a California native annual found in northern coastal and San Francisco Bay bioregions on sandy, gravelly seashores at elevations below 10 meters. Flowering from July to October, this plant produces white to pink flowers in small clusters along its prostrate to ascending stems. Growing up to 50 centimeters long with succulent green, ribbed stems that branch from the base, it develops distinctive elliptic to elliptic-obovate leaves 20 to 35 millimeters long. Its leaves have flat margins and obtuse tips, with small ocreae (stipule-like sheaths) 4 to 12 millimeters long that disintegrate into fibers. The fruit is widely ovate, 3 to 3.7 millimeters long, with a shiny brown to dark-brown surface and a distinctive beak-like tip.
Identification and appearance
Key characters: 19 sympatric species; key features are maritime habitat, succulent leaves, beaked fruits
Habitat and range
Habitat: Sandy, gravelly seashores
Elevation: < 10 m
Outside California: to Alaska, eastern Canada, Maine
Bloom period
Polygonum fowleri subsp. fowleri blooms Jul-Oct.
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 fowleri subsp. fowleri native to California?
Yes. Polygonum fowleri subsp. fowleri is native to California (recorded as native).
When does Polygonum fowleri subsp. fowleri bloom?
Polygonum fowleri subsp. fowleri blooms Jul-Oct.
What plant family does Polygonum fowleri subsp. fowleri belong to?
Polygonum fowleri subsp. fowleri is in the Polygonaceae family, genus Polygonum.
What habitat does Polygonum fowleri subsp. fowleri grow in?
Polygonum fowleri subsp. fowleri grows in Sandy, gravelly seashores.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · 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.