Triadenum

Triadenum, known as marsh St. John's worts,^[2] is a small genus of flowering plants in the family Hypericaceae. The genus is characterized by opposite, blunt-tipped leaves and pink flowers with 9 stamens. They are distributed in North America and eastern Asia.

Triadenum
Triadenum virginicum
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Malpighiales
Family:	Hypericaceae
Tribe:	Cratoxyleae
Genus:	Triadenum Raf.
Type species
T. fraseri (Spach) Gleason
Synonyms[1]
Gardenia Colden Hypericum L. sect. Elodea Choisy

Acceptance of this genus is varied. Kew's Plants of the World Online^[3] and the Database of Vascular Plants of Canada (VASCAN)^[4] treat it as a junior synonym of Hypericum and the Flora of North America^[1] and Flora of China^[5] 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.^[6] Under Hypericum, the species are mostly treated as the section Hypericum sect. Elodea.^[7]

Species

Triadenum contains the following 6 species according to Flora of North America and Flora of China:^[1][5]

• Triadenum breviflorum (Wall.)
• Triadenum fraseri (Spach) Gleason
• Triadenum japonicum (Thunb.)
• Triadenum tubulosum (Walter) Gleason
• Triadenum virginicum (L.) Raf.
• Triadenum walteri (J.F.Gmel.) Gleason