''Triadenum'', known as marsh St. John's worts, is a small
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of
flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
s in the
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Hypericaceae
Hypericaceae is a plant family in the order Malpighiales, comprising six to nine genera and up to 700 species, and commonly known as the St. John's wort family. Members are found throughout the world apart from extremely cold or dry habitats. '' ...
. The genus is characterized by opposite, blunt-tipped leaves and pink flowers with 9
stamens. They are distributed in North America and eastern Asia.
Acceptance of this genus is varied.
Kew
Kew () is a district in the London Borough of Richmond upon Thames. Its population at the 2011 census was 11,436. Kew is the location of the Royal Botanic Gardens ("Kew Gardens"), now a World Heritage Site, which includes Kew Palace. Kew is a ...
's
Plants of the World Online and the Database of Vascular Plants of Canada (VASCAN) treat it as a junior synonym of ''
Hypericum
''Hypericum'' is a genus of flowering plants in the family Hypericaceae (formerly considered a subfamily of Clusiaceae). The genus has a nearly worldwide distribution, missing only from tropical lowlands, deserts and polar regions. Many ''Hy ...
'' and the ''
Flora of North America'' and ''
Flora of China
The flora of China consists of a diverse range of plant species including over 39,000 vascular plants, 27,000 species of fungi and 3000 species of bryophytes.Wu, Z. Y., P. H. Raven & D. Y. Hong, eds. 2006. Flora of China. Vol. 22 (Poaceae). S ...
'' treat it as separate. The situation arises from B. R. Ruhfel et al. (2011)'s genetic study describing ''Triadenum'' as subsumed under ''Hypericum'' and later genetic results disagreeing with this assessment. Under ''Hypericum'', the species are mostly treated as the section ''Hypericum'' sect. ''Elodea''.
Species
''Triadenum'' contains the following 6 species according to ''Flora of North America'' and ''Flora of China'':
* ''
Triadenum breviflorum''
(Wall.)
* ''
Triadenum fraseri''
* ''
Triadenum japonicum''
(Thunb.)
* ''
Triadenum tubulosum''
* ''
Triadenum virginicum
''Hypericum virginicum'' (''Triadenum virginicum''), the marsh St. Johns-wort or Virginia marsh St. Johnswort, is a species of flowering plant in the family Hypericaceae. It is native to the central and eastern United States and eastern Canada.
...
''
* ''
Triadenum walteri''
References
Malpighiales genera
Hypericaceae
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