I have seen the same plant called: Hoya multiflora Centrostemma multiflora and Cyrtoceras floribundum Does anyone know which of these is the correct name or all they all synonyms and can be correctly used.
Hoya multiflora is the most correct as the latter two designations were described in publication after H. multiflora.
Thats not the reason why. Centrostemma and Cyrtoceras are now considered synonymous with Hoya and Hoya floribunda is now considered synonymous with Hoya multiflora.