Both these principles are regulated and limited. To avoid undesirable effects of priority, conservation of a name is possible. Above the taxonomic rank of family very few hard rules apply (e.g. see descriptive botanical names).
The ICBN can only be changed by an International Botanical Congress (IBC), with the International Association for Plant Taxonomy providing the supporting infrastructure. The present edition is the Vienna Code (2006), based on the decisions of the XVII IBC at Vienna 2005. This was preceded by the St Louis Code (2000) and the Tokyo Code (1994), both available online. Each new edition supersedes the earlier editions and is retroactive back to 1753, except where expressly limited.
Botanical nomenclature is independent of zoological and bacteriological nomenclature, which are governed by their own Codes (see Nomenclature Codes).
The ICBN applies not only to plants, as they are now defined, but also to other organisms traditionally studied by botanists. This includes blue-green algae (Cyanobacteria); fungi, including chytrids, oomycetes, and slime moulds; photosynthetic protists and taxonomically related non-photosynthetic groups. There are special provisions in the ICBN for some of these groups, as there are for fossils.
For the naming of cultivated plants there is a separate code, the International Code of Nomenclature for Cultivated Plants. This gives supplementary rules and recommendations.