Royal New Zealand Institute of Horticulture: The mission of the RNZIH is to encourage, promote, and improve horticulture in New Zealand.
The Royal Horticultural Society: Britain's Gardening Charity, founded in 1804 to encourage the science, art, and practice of horticulture in all its branches.
The Royal Horticultural Society of Ireland: Member-led society dedicated to promoting the knowledge, skill, and practice of horticulture, arboriculture and floral art. Founded in 1816