List of the largest genera of flowering plants


There are 57 genera of flowering plants estimated to contain at least 500 described species. The largest of these is currently the legume genus Astragalus, with over 3,000 species.
The sizes of plant genera vary widely from those containing a single species to genera containing thousands of species, and this disparity became clear early in the history of plant classification. The largest genus in Carl Linnaeus' seminal Species Plantarum was Euphorbia, with 56 species; Linnaeus believed that no genus should contain more than 100 species.
Part of the disparity in genus sizes is attributable to historical factors. According to a hypothesis published by Max Walters in 1961, the size of plant genera is related to the age, not of the taxon itself, but of the concept of the taxon in the minds of taxonomists. Plants which grew in Europe, where most of the early taxonomy was based, were therefore divided into relatively small genera, while those from the tropics were grouped into much larger and more heterogeneous genera. Likewise, plants which shared common medicinal properties, such as the many species of Euphorbia, were united into a single genus, while plants of diverse uses, such as the grasses, were split into many genera. Where there were many classical names for groups of plants, such as in Apiaceae / Umbelliferae or Brassicaceae / Cruciferae, small genera were defined, whereas groups not subdivided by classical authors remained as larger genera, such as Carex. A number of biological factors also influence the number of species. For instance, the occurrence of apomixis allows the recognition of large numbers of agamospecies, and such taxa have helped to bolster genera such as Ranunculus and Potentilla.
The introduction of infrageneric taxa in the 19th century by botanists including Augustin Pyrame de Candolle allowed the retention of large genera that would otherwise have become unwieldy. E. J. H. Corner believed that studying large genera might enable greater insights into evolutionary biology, and he concentrated his efforts on large tropical genera such as Ficus.

Largest genera

A total of 57 genera of flowering plants contain at least 500 species, according to a 2004 analysis by the botanical taxonomist David Frodin. The actual numbers of species are imprecisely known, as many of the genera have not been the subject of recent monographs. For instance, estimates of the number of species in the orchid genus Pleurothallis range from 1,120 to 2,500. Genera from other groups of vascular plants, but which have similarly large numbers of species, include Selaginella, Asplenium and Cyathea.
is the largest flowering plant genus, with more than 3,200 species, including Astragalus agnicidus.|alt=A legume with inflorescences of up to 40 elongated, ivory-coloured flowers, and pinnate leaves with many pairs of leaflets.
 is the second largest flowering plant genus, with more than 2,000 species, including Bulbophyllum guttulatum.|alt=Five orchid flowers, each with spotted tepals and a pink labellum.
is the third largest flowering plant genus, with more than 1,900 species, including Psychotria mariniana.|alt=A shrub with large, leathery, simple leaves, and bearing clusters of round, green fruit.
 is the fourth largest flowering plant genus, with more than 1,800 species, including Euphorbia amygdaloides.|alt=A group of unbranched herbs grow beside a plant label. The upper leaves and bracts grade from green to yellow.
is the fifth largest flowering plant genus, with more than 1,700 species, including Carex pilulifera.|alt=Several small, grass-like plants with thin leaves, each with a stalk bearing a cluster of small round fruits.
RankGenusSpeciesFamilySpecies list
1Astragalus 3,270FabaceaeList of Astragalus species
2Bulbophyllum 2,032OrchidaceaeList of Bulbophyllum species
3Psychotria 1,951RubiaceaeList of Psychotria species
4Euphorbia 1,836EuphorbiaceaeList of Euphorbia species
5Carex 1,795CyperaceaeList of Carex species
6Begonia 1,484BegoniaceaeList of Begonia species
7Dendrobium 1,371OrchidaceaeList of Dendrobium species
8Acacia c. 1,353FabaceaeList of Acacia species
9Solanum c. 1,250SolanaceaeList of Solanum species
10Senecio c. 1,250AsteraceaeList of Senecio species
11Croton 1,223EuphorbiaceaeList of Croton species
12Pleurothallis 1,120+OrchidaceaeList of Pleurothallis species
13Eugenia 1,113MyrtaceaeList of Eugenia species
14Piper 1,055PiperaceaeList of Piper species
15Ardisia 1,046PrimulaceaeList of Ardisia species
16Syzygium 1,041MyrtaceaeList of Syzygium species
17Rhododendron c. 1,000EricaceaeList of Rhododendron species
18Miconia 1,000MelastomataceaeList of Miconia species
19Peperomia 1,000PiperaceaeList of Peperomia species
20Salvia 945LamiaceaeList of Salvia species
21Erica 860EricaceaeList of Erica species
22Impatiens 850BalsaminaceaeList of Impatiens species
23Cyperus 839CyperaceaeList of Cyperus species
24Phyllanthus 833PhyllanthaceaeList of Phyllanthus species
25Allium 815AmaryllidaceaeList of Allium species
26Epidendrum 800OrchidaceaeList of Epidendrum species
27Vernonia 800–1,000AsteraceaeList of Vernonia species
28Lepanthes c. 800OrchidaceaeList of Lepanthes species
29Anthurium 789AraceaeList of Anthurium species
30Diospyros 767EbenaceaeList of Diospyros species
31Ficus 750Moraceae
32Indigofera 700+Fabaceae
33Justicia c. 700AcanthaceaeList of Justicia species
34Silene 700Caryophyllaceae
35Oxalis 700Oxalidaceae
36Crotalaria 699Fabaceae
37Centaurea 695Asteraceae
38Cassia 692Fabaceae
39Eucalyptus 681MyrtaceaeList of Eucalyptus species
40Oncidium 680Orchidaceae
41Galium 661RubiaceaeList of Galium species
42Cousinia 655Asteraceae
43Ipomoea 650Convolvulaceae
44Dioscorea 631Dioscoreaceae
45Cyrtandra 622Gesneriaceae
46Helichrysum 600Asteraceae
47Ranunculus 600RanunculaceaeList of Ranunculus species
48Habenaria 600OrchidaceaeList of Habenaria species
49Schefflera 584AraliaceaeList of Schefflera species
50Ixora 561RubiaceaeList of Ixora species
51Berberis 556BerberidaceaeList of Berberis species
52Quercus 531FagaceaeList of Quercus species
53Pandanus c. 520PandanaceaeList of Pandanus species
54Panicum 500+PoaceaeList of Panicum species
55Eria 500Orchidaceae
56Polygala 500Polygalaceae
57Potentilla 500RosaceaeList of Potentilla'' species