Calflora, a 501c3 non-profit
Taxon  Report  
Fallopia japonica  (Houtt.) Ronse Decr.
Japanese knotweed
Fallopia japonica is a perennial herb that is not native to California.
Cal-IPC rating: Moderate
Siskiyou Del Norte Modoc Humboldt Shasta Lassen Trinity Plumas Tehama Butte Mendocino Glenn Sierra Yuba Lake Nevada Colusa Placer Sutter El Dorado Yolo Alpine Napa Sonoma Sacramento Mono Amador Solano Calaveras Tuolumne San Joaquin Marin Contra Costa Alameda Santa Cruz Mariposa Madera San Francisco San Mateo Merced Fresno Stanislaus Santa Clara Inyo San Benito Tulare Kings Monterey San Bernardino San Luis Obispo Kern Santa Barbara Ventura Los Angeles Riverside Orange San Diego Imperial
Observation Search
(509 records)
one or more occurrences
within a 7.5-minute quadrangle

Bloom Period
Genus: Fallopia
Family: Polygonaceae  
Category: angiosperm  
PLANTS group:Dicot
Jepson eFlora section: eudicot

Wetlands: Occurs usually in non wetlands, occasionally in wetlands
Name Status:
Accepted by JEF
Alternate Names:
JEFPolygonum cuspidatum
JEFReynoutria japonica
JEFTiniaria japonica
PLANTSPolygonum cuspidatum
More information about  Fallopia japonica

USFS Fire Effects Information System: Three Asian Knotweeds

The Spruce landscaping journal: Overview of Control Methods.

USDA Species Profile: Japanese Knotweed Resources

Suggested Citation
Calflora: Information on California plants for education, research and conservation, with data contributed by public and private institutions and individuals, including the Consortium of California Herbaria. [web application]. 2022. Berkeley, California: The Calflora Database [a non-profit organization]. Available: https://www.calflora.org/   (Accessed: 09/30/2022).