Polygonum parryi
Parry's or prickly knotweed
Family: Polygonaceae · Type: Herb · Native
Polygonum parryi (Parry's or prickly knotweed) is a native California herb in the Polygonaceae family, recognized by very small cushion habit and spine-tipped leaves.
Parry's knotweed is a California native annual found in northwestern California, the Cascade Range, Sierra Nevada, San Francisco Bay Area, and Peninsular Ranges in vernally moist, open, sandy, rocky places at elevations of 500 to 2,000 meters. Flowering from May to July, this plant produces tiny flowers with red perianth and white margins, clustered closely in most leaf axils. Growing as a compact, cushion-like plant with erect green-brown stems just 2 to 5 centimeters tall, it forms a dense, low-growing cluster. Its leaves are remarkably narrow, lance-linear or awl-shaped, measuring 5 to 13 millimeters long and less than a millimeter wide, with spine-tipped edges and margins rolled underneath. The small dark-brown, shiny fruits are slightly protruding and approximately 1.2 to 1.6 millimeters long.
Identification and appearance
Key characters: 27 sympatric species; very small cushion habit and spine-tipped leaves
Habitat and range
Habitat: Vernally moist, open, sandy, rocky places
Elevation: 500-2000 m
Outside California: to Washington
Bloom period
Polygonum parryi blooms May-Jul.
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 parryi native to California?
Yes. Polygonum parryi is native to California (recorded as native).
When does Polygonum parryi bloom?
Polygonum parryi blooms May-Jul.
What plant family does Polygonum parryi belong to?
Polygonum parryi is in the Polygonaceae family, genus Polygonum.
What habitat does Polygonum parryi grow in?
Polygonum parryi grows in Vernally moist, open, sandy, rocky places.
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.