• Advisory Council on Historic Preservation 
• America Public Gardens Association
• American Society of Landscape Architects
• Association of Preservation Technology
• Canadian Museums Association
• Canadian Society of Landscape Architects
• Canadian Association of Professional Heritage Consultants
• The Centre for Landscape Research
• Conservation Study Institute
• Cultural Landscape Currents: NPS Historic Landscape Initiative
• The Cultural Landscape Foundation
• Dumbarton Oaks
• Foundation of Landscape Studies
• The Garden Club of America
• The Garden Conservancy
• Garden History Links
• Garden History Society
• Southern Garden History Society
• Heritage Canada Foundation
• ICOMOS
• International Federation of Landscape Architects (IFLA)
• Institute for Cultural Landscape Studies
• Internet Resources for Heritage Conservation, Archaelogy, and Historic Preservation
• IUCN/WCPA for Protected Landscapes
• Library of American Landscape History
• National Center for Preservation Technology and Training
• The National Trust, United Kingdom
• National Trust for Historic Preservation
• Ontario Heritage Trust
• Preservation Directory
• Preserve and Protect, Inc.
• UNESCO World Heritage