Master Gardeners
Canada, United States, American Horticultural Society Master Gardener Web, International Master Gardener Committee, Junior Master Gardener Program, MasterGardeners.com Your Link To Master Gardener P, State Coordinators, The Master Gardener Show, Tom Robb's Master Gardener Page
Regional
Australia, Canada, United States, Royal New Zealand Institute of Horticulture, The Royal Horticultural Society, The Royal Horticultural Society of Ireland
Wildflowers and Natives
Alberta Native Plant Council, Arizona Native Plant Society, Arkansas Native Plant Society, Association of Societies for Growing Australian Pl, Australian Plants Society - New South Wales Region, Australian Plants Society Sutherland Group, California Native Plant Society, Cartersville Garden Club - Wildflowers, Connecticut Botanical Society, Delaware Native Plant Society
Canadian Botanical Conservation Network
A registered charitable organization which helps conserve biological diversity through networking tools and conservation programs for botanical gardens and arboreta.
International Code of Nomenclature for Cultivated
An extensive list of worldwide contacts of associations organised in taxonomic order.
Lesbian Gardens
Special thoughts on growing plants, various links and member information.
The Brown Lawn Society
Organization encouraging environmentally friendly methods for lawn care such as the reuse of rainwater and natural pest collectors.
The Gardeners Club
A directory of all local and national gardening related clubs, societies and organisations in the UK.
The Mediterranean Garden Society
Resources for gardeners in the Mediterranean basin and similar climate regions.
The Professional Gardeners Guild
An organisation for gardeners employed in private gardens and estates. Based in the UK with members in European countries and the United States.