Calflora, a 501c3 non-profit
Distribution by County   6756    
Polygonum lapathifolium  L.

(not an active name)
Common knotweed,   Curlytop knotweed,   Willow smartweed,   Willow weed
Polygonum lapathifolium is an annual herb that is native to California, and also found elsewhere in North America and beyond.
also called Persicaria lapathifolia
Record Count by County

Alameda: 16 Los Angeles: 67 Riverside: 57 Solano: 39
Amador: 1 Madera: 3 Sacramento: 18 Sonoma: 10
Butte: 59 Marin: 9 San Bernardino: 63 Stanislaus: 5
Colusa: 14 Mariposa: 7 San Diego: 128 Sutter: 18
Contra Costa: 6 Mendocino: 2 San Francisco: 11 Tehama: 15
El Dorado: 8 Merced: 16 San Joaquin: 18 Trinity: 1
Fresno: 14 Modoc: 1 San Luis Obispo: 25 Tulare: 9
Glenn: 21 Mono: 6 San Mateo: 16 Tuolumne: 2
Humboldt: 5 Monterey: 19 Santa Barbara: 60 Ventura: 59
Imperial: 6 Napa: 22 Santa Clara: 28 Yolo: 13
Inyo: 11 Nevada: 6 Santa Cruz: 11 Yuba: 4
Kern: 18 Orange: 50 Shasta: 8
Lake: 7 Placer: 8 Sierra: 1
Lassen: 3 Plumas: 18 Siskiyou: 1

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]. 2024. Berkeley, California: The Calflora Database [a non-profit organization]. Available: https://www.calflora.org/   (Accessed: 12/22/2024).