Triadenum fraseri (L.) Raf. - Marsh St. John's Wort


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Triadenum fraseri - (image 1 of 4)



Family: Hypericaceae


Synonymous with Hypericum virginicum L. var. fraseri (Spach) Fern.


Bogs, marshes, moist calcareous sand, marly fens.




Newfoundland and Quebec west to MN and IA, south to CT, NY, OH, northern IN, NE, and in mountains to WV and TN.


Rhizomatous, glabrous perennial. Leaves sessile, opposite, ovate-oblong to elliptic, dotted with translucent glands and dark-spotted below. Flowers in terminal cymules; petals pink, 5; sepals 5, obtuse or rounded; ovary trilocular. Fruit ovoid or cylindric, 7-12 mm, rather abruptly narrow to the styles.


Flowers mid July to early September

Wetland indicator: Obligate

This species had me baffled for some time because I had never seen the flowers open. They seem to open for only a few hours of the day.


Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. Second Ed.

The New York Botanical Garden. Bronx, NY


Swink, F. and G. Wilhelm. 1994. Plants of the Chicago Region.
Indiana Academy of Science. The Morton Arboretum. Lisle, Illinois.




 Michael Hough 2005