Polygonum shastense
Shasta knotweed
no rights reserved · CC0
Family: Polygonaceae · Type: Shrub · Native
Polygonum shastense (Shasta knotweed) is a native California shrub in the Polygonaceae family, recognized by unique as the only perennial shrubby species with large flowers.
Shasta knotweed is a California native perennial found in the Sierra Nevada and High Cascade Mountains on rocky, gravelly slopes at elevations of 2,100 to 3,400 meters. Flowering from July to September, this plant produces delicate pink or white flowers in small clusters of 2 to 6 blooms. Growing with prostrate to ascending gnarled stems 5 to 40 centimeters long, the plant has a distinctive branched structure with brown, slightly angled stems. Its leaves are crowded toward the stem tips, with leathery lanceolate to elliptic blades 5 to 25 millimeters long, having margins rolled under and acute tips. The plant produces small, shiny brown fruits 3 to 4 millimeters long that are nestled among its densely clustered foliage.
Identification and appearance
Key characters: 24 sympatric species; unique as the only perennial shrubby species with large flowers
Habitat and range
Habitat: Rocky, gravelly slopes
Elevation: 2100-3400 m
California counties: Fresno, Shasta, Alpine, Tulare, Kern, Mono, Siskiyou, Madera, Trinity, Nevada, Lassen, Sierra, Placer, Amador, Mariposa, Plumas, Butte, Tehama, El Dorado, Tuolumne, Solano
Outside California: Oregon, Nevada
Bloom period
Polygonum shastense blooms Jul-Sep.
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 shastense native to California?
Yes. Polygonum shastense is native to California (recorded as native).
When does Polygonum shastense bloom?
Polygonum shastense blooms Jul-Sep.
Where in California does Polygonum shastense grow?
Polygonum shastense occurs in Fresno, Shasta, Alpine, Tulare, Kern, Mono, Siskiyou, Madera and other counties, at elevations of 2100-3400 m.
What plant family does Polygonum shastense belong to?
Polygonum shastense is in the Polygonaceae family, genus Polygonum.
What habitat does Polygonum shastense grow in?
Polygonum shastense grows in Rocky, gravelly slopes.
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.