Prior to the first International Botanical Congress, local congresses concerned with natural sciences generally had grown to be very large, and a more specialized but also international meeting was considered desirable.[{{cite book|author=Stafleu, F.A. |year=1970 |title= XI International Botanical Congress, University of Washington, Seattle, U.S.A., August 24–September 2, 1969. Proceedings |chapter= A century of botanical congresses |publisher=XI International Botanical Congress, Inc. |location=NC]
The fourth congress, which had as one of its principal purposes to establish laws of botanical nomenclature, was organized by la Société botanique de France, and took place in Paris in August 1867.[{{cite book |url=https://archive.org/stream/actesducongrsi1867inte#page/n9/mode/2up |title=Actes du Congrés international de botanique tenu a Paris en août 1867, sous les auspices de la Société botanique de France (1867)|author=Alphonse de Candolle |year=1867|publisher=Paris, G. Bailliére }}] The laws adopted were based on those prepared by Alphonse de Candolle. Regular international botanical and/or horticultural congresses were held but made no further changes to nomenclature until the 1892 meeting in Genoa,[ which made some small changes to the laws of nomenclature.][{{Cite web|url=https://archive.org/details/attidelcongress00penzgoog|title=Atti del Congresso botanico internazionale di Genova 1892|last=International Botanical Congress|location=Genoa|date=February 11, 1893|publisher=Genova, Tip. del R. Istituto sordo-muti|via=Internet Archive}}] Subsequent meetings are as follows in the table below. The "Code" column shows whether a code of nomenclature was adopted.
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! [{{cite web |url=http://www.biologie.uni-hamburg.de/b-online/ibc99/ibc/history.html |title=History of IBC |access-date=2006-08-10 |url-status=dead |archive-url=https://web.archive.org/web/20061011020629/http://www.biologie.uni-hamburg.de/b-online/ibc99/ibc/history.html |archive-date=2006-10-11 }}][{{cite journal|last=Nicolson |first=D.H.|year=1991|title=A History of Botanical Nomenclature|journal=Annals of the Missouri Botanical Garden|volume=78|issue=1|pages=33–56 |jstor=2399589 |doi=10.2307/2399589|url=https://www.biodiversitylibrary.org/part/35570 }}] !! Year !! City !! Country !! Code !! Major actions concerning nomenclature |
| I | 1900 | Paris | {{FRA}} | | Decisions on nomenclature deferred. |
| II | 1905 | Vienna | {{AUT}} | Yes | First binding Rules of Nomenclature; French became the official language of the meeting; requirement for Latin plant descriptions from 1908 onwards (not enforced); end of the Kew Rule. |
| III | 1910 | Brussels | {{BEL}} | Yes | Separate starting dates for nomenclature of fungi established. |
| IV | 1926 | Ithaca | {{USA}} | | Decisions on nomenclature deferred. |
| V | 1930 | Cambridge | {{UK}} | Yes | The type method incorporated; Latin requirement deferred until 1932; "absolute homonym rule" accepted, or "once a later homonym always illegitimate (unless conserved)", which altered the status of many names, including many that had previously been conserved.[{{cite journal|author1=Rickett, H.W. |author2=Stafleu, F.A. |year=1959|title=Nomina generica conservanda et rejicienda spermatophytorum|journal=Taxon|volume=8|issue=7|pages=213–243 |doi=10.2307/1217883|jstor=1217883 |url=http://www.repository.naturalis.nl/document/572525 }}] The Cambridge Code was not published until 1935.[ This code was accepted by previous proponents of the American Code, ending a period of schism.][{{cite journal |author=Weatherby, C.A. |year=1949|title=Botanical Nomenclature Since 1867|journal=American Journal of Botany |volume=36 |issue=1|pages=5–7|jstor=2438113|doi=10.2307/2438113 |pmid=18124191}}] |
| VI | 1935 | Amsterdam | {{NED}} | | English became the official language of the Congress, replacing French. No formal Code was published. |
| VII | 1950 | Stockholm | {{SWE}} | Yes | Adoption of the first International Code of Nomenclature for Cultivated Plants;[ arbitrary dates defined for some foundational works; decision to hold future congresses every five years (except four years for the next one). For fossil plants, organ genera and form genera were introduced.] |
| VIII | 1954 | Paris | {{FRA}} | Yes | Two additional principles added, II and III, dealing with types and with priority. Proposals to conserve or reject specific names were rejected, but a committee was established to find ways to improve the stability of names.[{{cite journal |author=Stafleu, F.A. |year=1954 |title=Nomenclature at the Paris Congress |journal=Taxon |volume=3 |issue=8 |pages=217–225 |doi=10.2307/1216598 |jstor=1216598}}] |
| IX | 1959 | Montreal | {{CAN}} | Yes | Presentation of a completely reworked list of conserved and rejected names necessitated by changes made at the 1930 congress,[ but the list for species was not accepted.{{refn|group=nb|"The proposals concerning the question of possible nomina specifica conservanda c.q. rejicienda did not result in any legislative action but were followed by an attempt to assess first the real scope of the problem before changing the rules. This may seem a minor step forward. In fact I believe it is the first real progress that has been made towards solving this difficult problem.][{{citation |author1=Lanjouw, J. |author2=Baehni, C. |author3=Robyns, W. |author4=Ross, R. |author5=Rousseau, J. |author6=Schopf, J.M. |author7=Schulze, G.M. |author8=Smith, A.C. |author9=Vilmorin, R.d. |author10=Stafleu, F.A. |year=1961 |title=Code International de la Nomenclature Botanique/International Code of Botanical Nomenclature/Internationaler Code der botanischen Nomenklatur |publisher=International Bureau for Plant Taxonomy and Nomenclature of the International Association for Plant Taxonomy |location=Utrecht |display-authors=etal}}] Preface by J. Lanjouw}} Decision that rules of priority do not apply above the rank of family.[ Starting point for family names to be Antoine Laurent de Jussieu's Genera Plantarum 1789.][ Choice among French, English, and German official codes of English as the standard in case of discrepancy.{{refn|group=nb|"As before, the Nomenclature Section decided that the Code should be published in English, French and German languages. The three texts are all official, but, should there be any inconsistency between the versions, it is agree to regard the English one arbitrarily as correct."][ Preface by J. Lanjouw}}] |
| X | 1964 | Edinburgh | {{UK}} | Yes | No major changes to the code.[{{cite journal |author=Stafleu, F.A. |year=1964 |title=Nomenclature at Edinburgh |journal=Taxon |volume=13 |issue=8 |pages=273–282 |doi=10.2307/1216194 |jstor=1216194}}] |
| XI | 1969 | Seattle | {{USA}} | Yes | Established the International Association of Bryologists. |
| XII | 1975 | Leningrad | {{USSR}} | Yes | Official versions of the code in English, French, and German (the English version to take precedence in case of discrepancy); rejection of species names allowed in a few special cases; organ-genera for fossil plants are eliminated, replaced by form-genera. |
| XIII | 1981 | Sydney | {{AUS}} | Yes | Official versions of the code in English, French, and German (the English version to take precedence in case of discrepancy); conservation procedure (and rejection) extended to species names "of major economic importance"; fungi starting date restored to 1753 with sanctioned name status established; the types of genera and higher categories become the types of species (i.e., the taxa themselves are no longer types,[This is a contrast to the ICZN.] only specimens or illustrations). |
| XIV | 1987 | Berlin | {{GER}} | Yes | Official version of the code only in (British) English; later translations in French, German, and Japanese; conservation extended to species names that represent the type of a conserved generic name. |
| XV | 1993 | Tokyo | {{JPN}} | Yes | Moves towards registration of plant names; extensive re-arrangement of the nomenclature code; official version of the code only in (British) English; later translations in Chinese, French, German, Italian, Japanese, Russian, and Slovak; conservation extended to all species names; rejection permitted for any name that would cause a disadvantageous nomenclatural change; epitype concept introduced. |
| XVI | 1999 | St. Louis | {{USA}} | Yes | Refinement of type requirements; illustrations as types mostly forbidden from 1958; morphotaxa for fossils. Proposals defeated included the BioCode and registration of plant names. |
| XVII | 2005 | Vienna | {{AUT}} | Yes | Morphotaxa and regular taxa for fossils; illustrations as types mostly forbidden from 2007; glossary added to the code of nomenclature. |
| XVIII | 2011 | Melbourne | {{AUS}} | Yes | Electronic publication permitted; registration of fungal names; English or Latin descriptions (or diagnoses) from 2012; the concepts of anamorph and teleomorph (for fungi) and morphotaxa (for fossils) eliminated. |
| XIX | 2017 | Shenzhen | {{CHN}} | Yes | |
| XX | 2024 | Madrid | {{SPN}} | Yes | The 2023 IBC in Brazil was cancelled due to COVID-19 pandemic, combined with the serious economic impact and social disruption. The XX IBC was rescheduled to Madrid in 2024.[{{cite journal |author=Knapp, S. & Wen, J. |year=2021|title=INTERNATIONAL BOTANICAL CONGRESS MOVING TO MADRID IN 2024|journal=Taxon |volume=70 |issue=3|pages=690–698|doi=10.1002/tax.12522}}] Hundreds of kaffir-related species names were voted to be changed.[{{Cite web |author=Rodrigo Pérez Ortega, Erik Stokstad |date=2024-07-24 |title=In a first, botanists vote to remove offensive plant names from hundreds of species |url=https://www.science.org/content/article/botanists-vote-to-remove-offensive-plant-names-from-hundreds-of-species |website=Science |language=en |doi=10.1126/science.z3dptab}}] |
| XXI | 2029 | Cape Town | {{RSA}} | |
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