The RHS is part of a world-wide network of International Cultivar Registration Authorities (ICRAs), which play a vital role in promoting uniformity, accuracy and stability in the naming of cultivated plants. It is a non-statutory, voluntary process that benefits the whole horticultural community. ICRAs are appointed by the International Society for Horticultural Science through its Commission for Nomenclature and Registration.

Most important horticultural genera are covered by an ICRA and a full list of these can be found as Appendix I of the International Code of Nomenclature for Cultivated Plants 2004. Updated details are also available online.

The RHS is ICRA for nine major groups, currently processing well over 4,000 names a year in the areas listed below. The Society publishes annual plant registers relating to these groups. Regular supplements detailing new registrations are published for all these groups and, from time to time, new comprehensive International Registers are offered for sale.