- American Public Gardens Association
- The Arnold Arboretum
- Bartram's Gardens
- Blithewold Mansion, Gardens and Arboretum
- Brandywine River Museum
- Buchart Gardens
- Cheekwood Botanical Gardens and Art Museum
- Dumbarton Oaks
- Garden History Links
- Goodell Gardens and Homestead
- Historic New England
- International Lilac Society
- Landis Valley Museum Heirloom Seed Project
- Longwood Gardens
- Massachusetts Horticultural Society
- Master Gardens
- Monticello
- Monticello - Jefferson Center for Historic Plants
- Niagra Parks (Nature and Gardens section)
- NY Botanical Gardens
- Old House Gardens
- Old Sturbridge Village
- Pennsylvania Horticultural Society
- Pennsylvania Native Plant Society
- Penn State Master Gardener Program
- Penn State University Consumer Horticulture Center
- Wintherthur