This list of systems of plant taxonomy presents "taxonomic systems" used in plant classification.
A taxonomic system is a coherent whole of taxonomic judgments on circumscription and placement of the considered taxa. It is only a "system" if it is applied to a large group of such taxa (for example, all the flowering plants).
The Cronquist system is a taxonomic classification system of flowering plants. It was developed by Arthur Cronquist in a series of monographs and texts, including The Evolution and Classification of Flowering Plants (1968; 2nd edition, 1988) and An Integrated System of Classification of Flowering Plants (1981) (see Bibliography).
Cronquist's system places flowering plants into two broad classes, Magnoliopsida (dicotyledons) and Liliopsida (monocotyledons). Within these classes, related orders are grouped into subclasses. While the scheme was widely used, in either the original form or in adapted versions, many botanists now use the Angiosperm Phylogeny Group classification for the orders and families of flowering plants, first developed in 1998. The system as laid out in Cronquist's An Integrated System of Classification of Flowering Plants (1981) counts 64 orders and 321 families in class Magnoliopsida and 19 orders and 65 families in class Liliopsida.
The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was published in 2016, seven years after its predecessor the APG III system was published in 2009, and 18 years after the first APG system was published in 1998. In 2009, a linear arrangement of the system was published separately; the APG IV paper includes such an arrangement, cross-referenced to the 2009 one.
Compared to the APG III system, the APG IV system recognizes five new orders (Boraginales, Dilleniales, Icacinales, Metteniusales and Vahliales), along with some new families, making a total of 64 angiosperm orders and 416 families. In general, the authors describe their philosophy as "conservative", based on making changes from APG III only where "a well-supported need" has been demonstrated. This has sometimes resulted in placements that are not compatible with published studies, but where further research is needed before the classification can be changed.
The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy being developed by the Angiosperm Phylogeny Group (APG). Published in 2009, it was superseded in 2016 by a further revision, the APG IV system.
Along with the publication outlining the new system, there were two accompanying publications in the same issue of the Botanical Journal of the Linnean Society:
The APG system (Angiosperm Phylogeny Group system) of plant classification is the first version of a modern, mostly molecular-based, system of plant taxonomy. Published in 1998 by the Angiosperm Phylogeny Group, it was replaced by the improved APG II in 2003, APG III system in 2009 and APG IV system in 2016.
A taxonomic system for seed plants was published in Bentham and Hooker's Genera plantarum ad exemplaria imprimis in herbariis kewensibus servata definita in three volumes between 1862 and 1883.
George Bentham (1800–1884) and Joseph Dalton Hooker (1817–1911) were British botanists who were closely affiliated to the Royal Botanic Gardens, Kew, in England. Their system of botanical taxonomy was based on the principle of natural affinities and is considered as pre-Darwinian as it does not take evolution into account. The Genera plantarum classified an estimated 97,205 species into 202 families and 7,569 genera.
Abietoideae is a subfamily of the conifer family Pinaceae. The name is from the genus Abies (firs), which contains most of the species in the genus. Six genera are currently assigned to this subfamily: Abies, Cedrus, Keteleeria, Nothotsuga, Pseudolarix, and Tsuga. The group was formerly treated as a separate family, the Abietaceae, by some plant taxonomy systems, such as the Wettstein system.