Polygonum bolanderi
Bolander's knotweed
(c) Ken-ichi Ueda, some rights reserved (CC BY) · licence
Family: Polygonaceae · Type: Shrub · Native
Polygonum bolanderi (Bolander's knotweed) is a native California shrub in the Polygonaceae family, recognized by perennial woody habit and recurved flower lobes distinctive.
Bolander's knotweed is a California native perennial herb found in northwestern California, especially Napa County, the California Ranges, and northern and central Sierra Nevada in open, dry, gravelly, rocky places at elevations of 300 to 1,500 meters. Flowering from June to November, this plant produces delicate white or pink flowers less than 4 millimeters long, with lobes that are elliptic-oblong and slightly recurved. Growing with erect, wiry stems 20 to 60 centimeters tall that become gnarled with age, it develops a distinctive branching pattern. Its leaves are crowded near the stem tips, extremely narrow and linear, measuring just 3 to 15 millimeters long and less than 2 millimeters wide, with spine-tipped margins. The fruit is a small, shiny light-brown structure that remains enclosed within the flower's perianth.
Identification and appearance
Key characters: 25 sympatric species; perennial woody habit and recurved flower lobes distinctive
Habitat and range
Habitat: Open, dry, gravelly, rocky places
Elevation: 300-1500 m
California counties: Napa, Tehama, Butte, Shasta, Humboldt, Tuolumne, Solano, Sonoma, El Dorado, Placer, Lake, Glenn, Calaveras, Mariposa
Bloom period
Polygonum bolanderi blooms Jun-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 bolanderi native to California?
Yes. Polygonum bolanderi is native to California (recorded as native).
When does Polygonum bolanderi bloom?
Polygonum bolanderi blooms Jun-Nov.
Where in California does Polygonum bolanderi grow?
Polygonum bolanderi occurs in Napa, Tehama, Butte, Shasta, Humboldt, Tuolumne, Solano, Sonoma and other counties, at elevations of 300-1500 m.
What plant family does Polygonum bolanderi belong to?
Polygonum bolanderi is in the Polygonaceae family, genus Polygonum.
What habitat does Polygonum bolanderi grow in?
Polygonum bolanderi grows in Open, dry, gravelly, rocky places.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.