Polygonum argyrocoleon
Persian knotweed
(c) Sula Vanderplank, some rights reserved (CC BY) · licence
Family: Polygonaceae · Type: Herb · Not Native
Polygonum argyrocoleon (Persian knotweed) is a non-native California herb in the Polygonaceae family, recognized by blue-green leaves and saline habitat preference are key.
Persian knotweed is a naturalized perennial found in southern California, particularly in disturbed places and saline soils at elevations below 1,000 meters. Flowering from June to October, this plant produces green-white flowers with pink margins in small, crowded clusters. Growing with decumbent to erect stems 15 to 100 centimeters tall, it has distinctive ribbed green branches that typically emerge from the base. Its lance-linear leaves are blue-green, 15 to 50 millimeters long and 2 to 8 millimeters wide, with flat margins and acute tips. The plant has distinctive ocreae that disintegrate into curly or straight fibers, giving it a unique textural appearance in disturbed landscapes.
Identification and appearance
Key characters: 30 sympatric species; blue-green leaves and saline habitat preference are key
Habitat and range
Habitat: Disturbed places, often in saline soils
Elevation: < 1000 m
California counties: Los Angeles, Ventura, San Bernardino, Imperial, Orange, Riverside, San Diego, Kings, Merced, Inyo, Lake, Santa Clara, Fresno, San Luis Obispo, Kern, Siskiyou, Solano, El Dorado, Santa Barbara, San Francisco, Yolo, Marin, Monterey, San Mateo, Lassen, Tulare, Contra Costa, Sierra, Stanislaus
Outside California: southern and western United States, native to southwestern Asia
Bloom period
Polygonum argyrocoleon blooms Jun-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 argyrocoleon native to California?
No. Polygonum argyrocoleon is not native to California (recorded as not native).
When does Polygonum argyrocoleon bloom?
Polygonum argyrocoleon blooms Jun-Oct.
Where in California does Polygonum argyrocoleon grow?
Polygonum argyrocoleon occurs in Los Angeles, Ventura, San Bernardino, Imperial, Orange, Riverside, San Diego, Kings and other counties, at elevations of < 1000 m.
What plant family does Polygonum argyrocoleon belong to?
Polygonum argyrocoleon is in the Polygonaceae family, genus Polygonum.
What habitat does Polygonum argyrocoleon grow in?
Polygonum argyrocoleon grows in Disturbed places, often in saline soils.
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.