Polygonum austiniae
Mrs. austin's knotweed, Mrs. Austin's Knotweed
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Family: Polygonaceae · Type: Annual · Native
Polygonum austiniae (Mrs. austin's knotweed) is a native California annual in the Polygonaceae family, recognized by distinctive ovate to elliptic leaves and montane habitat.
Mrs. austin's knotweed is a California native annual found in the Modoc Plateau bioregion in dry to moist flats on banks, sagebrush plains, and ponderosa-pine forest at elevations of 1,300 to 1,600 meters. Flowering from June to September, this plant produces small green to purple flowers with narrow white-margined perianth segments in spike-like clusters. Growing with ascending to erect stems 5 to 10 centimeters tall, often branching from the base and having a slightly purple-green coloration. Its leaves are small and ovate to elliptic, 5 to 15 millimeters long with papillate-toothed margins and acute tips. The fruit is a shiny black, elliptic to obovate seed approximately 2 to 2.5 millimeters long.
Identification and appearance
Key characters: 16 sympatric species; distinctive ovate to elliptic leaves and montane habitat
Habitat and range
Habitat: dry to moist flats on banks, sagebrush plains, ponderosa-pine forest
Elevation: 1300-1600 m
Outside California: to British Columbia, Montana, Wyoming
Bloom period
Polygonum austiniae blooms Jun-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 austiniae native to California?
Yes. Polygonum austiniae is native to California (recorded as native).
When does Polygonum austiniae bloom?
Polygonum austiniae blooms Jun-Sep.
What plant family does Polygonum austiniae belong to?
Polygonum austiniae is in the Polygonaceae family, genus Polygonum.
What habitat does Polygonum austiniae grow in?
Polygonum austiniae grows in dry to moist flats on banks, sagebrush plains, ponderosa-pine forest.
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.