I am currently a personal member of the following societies in the UK. This does not mean that any of the societies I belong to endorse, or have any connection to my business activities.
British Cactus and Succulent Society.
http://www.bcss.org.uk
British Pteridological Society.
https://britishfernsociety.org.uk/
Royal Horticultural Society.
https://www.rhs.org.uk/
National Auricula & Primula Society Northern Section.
https://www.auriculas.org.uk/
British Iris Society.
https://www.britishirissociety.org.uk/
RHS Lily Group.
https://rhslilygroup.org/