- American Association of Amateur Arborists - A loose association of individuals and groups interested in learning more about trees and other woody plants.
- American Conifer Society - Association for the development, conservation, and propagation of conifers, with an emphasis on those that are dwarf or unusual. Photo gallery, database, information about membership and journal.
- British Conifer Society - Organization for gardeners and collectors of ornamental, dwarf and rare conifers, owners and managers of arboreta and nurseries, and professional botanists. Photo gallery and database, excerpts from the journal.
- Magnolia Society International - A worldwide organization of gardeners, nurserymen and other people who are devoted to the appreciation and study of magnolias.
