''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 extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

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 Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

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

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filame ...

s. 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 ...

Plants of the World Online Plants of the World Online (POWO) is an online database published by the Royal Botanic Gardens, Kew. It was launched in March 2017 with the ultimate aim being "to enable users to access information on all the world's known seed-bearing plants by ...

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 ''Hype ...

'' and the ''

Flora of North America The ''Flora of North America North of Mexico'' (usually referred to as ''FNA'') is a multivolume work describing the native plants and naturalized plants of North America, including the United States, Canada, St. Pierre and Miquelon, and Greenla ...

'' 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). Sc ...

'' 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 fraseri'', commonly known as bog St. John's wort, Fraser's St. John's wort, and Fraser's marsh St. John's wort, is a perennial flowering plant in the family Hypericaceae that grows in wetlands of Canada and the northern United States. ...

'' * '' 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 {{Triadenum-stub