The International Code of Nomenclature for Cultivated Plants (ICNCP) regulates the naming of cultivars, cultivar Groups and graft-chimaeras. Examples are
⇒ Clematis alpina 'Ruby' : a cultivar within a species
⇒ Magnolia 'Elizabeth' : a hybrid between at least two species
⇒ Rhododendron boothii Mishmiense Group: a Group name
⇒ Crataegomespilus : a graft-chimaera of Crataegus and Mespilus.
Note that the ICNCP does not regulate trademarks for plants: trademarks are regulated by the law of the land involved. Nor does the ICNCP regulate the naming of plant varieties.
Orchids have a Code of their own that operates within the limits set by the ICNCP.