{{source}}Washington State county boundaries from Washington Department of Natural Resources. Acres of distribution calculated from following maps published by the Washington State Department of Agriculture in 2011: Knotweed, Bohemian, "Polygonum bohemicum" Distribution 2011. Giant, "Polygonum sachalinense" Distribution 2011. Himalayan, "Polygonum polystachyum" Distribution 2011. Knotweed, Japanese, "Polygonum cuspidatum" Distribution 2011. PRISM projects extracted from PRISM website Project Search @ https://secure.rco.wa.gov/PRISM/search/ProjectSearch.aspx in 2015.ArcGIS FeatureLayerhttps://hub.arcgis.com/datasets/3410e9d7ac3c46efaf7bcfd5eb50e8c6_0engState of Washington Geospatial Open Data PortalPublicKnotweed Projects in PRISM [Washington (State)]Web servicesWashington (State)Last Modified: 2018-12-13