American Brugmansia and Datura Society
Offers culture information, searchable plant database, registry and photographs.
American Hibiscus Society
Includes membership information, publications, chapter locations, events, and links.
International Lilac Society
Formed in 1971 to stimulate interest in the genus Syringa and to promote its use in public and private landscaping.
National Chrysanthemum Society
Promotes the propagation and cultivation of the chrysanthemum and increase the bonds of fellowship among growers of the chrysanthemum.