Vascular Plants of North Carolina
Account for Greater Marsh St. John's-wort - Triadenum walteri   (J.F. Gmelin) Gleason
Members of Hypericaceae:
Members of Triadenum with account distribution info or public map:
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Section 6 » Order Theales » Family Hypericaceae
Author(J.F. Gmelin) Gleason
DistributionPresent over nearly all of the Coastal Plain, and scattered over the Piedmont; seemingly absent in the northwestern Piedmont and nearly all of the Mountains.

This is a Southern species that ranges north to southern NJ and southeastern MO, and south to northern FL and eastern TX. It is mostly absent in the Appalachians.
AbundanceCommon in the northern half of the Coastal Plain, and fairly common in the southern half, except scarce in the Sandhills. Uncommon in the Piedmont, except very rare to absent in the northwestern portion. Very rare in the far southwestern Mountains. For whatever reason, the soil types or habitats in the northern Coastal Plain favor this species, as opposed to the similar T. virginicum.
HabitatThis is a species of a wide array of wetlands, found in more habitats than is T. virginicum. It seems to favor brownwater (or richer) mud and soil than the other species, being found in swamps, pond and lake margins, marshes, floodplain pools, and other wet ground. The fact that is it not widely recorded in Sandhills counties makes it clear that H. walteri is mainly not found in acidic/blackwater habitats very often.
PhenologyBlooms in August and September, and fruits not long after blooming.
IdentificationThis is an herbaceous species and grows to an average of 2 feet tall; it typically is found in colonies. The generally elliptic leaves grow to about 2-2.5 inches long, with a rounded tip and rounded to tapered base, with a distinct petiole that averages about 1/4-inch long. The distinct petiole separates this species from the similar T. virginicum and T. tubulosum. All three have pink, five-petaled flowers in leaf axils and branch tips – not helpful in separation from the others.
Taxonomic CommentsA few older references subsumed this species into T. tubulosum, as T. tubulosum var. walteri. Weakley (2020) has moved the pink-flowered former Hypericum species to Triadenum.

Other Common Name(s)Walter’s Marsh St. John’s-wort
State RankS4 [S5]
Global RankG5
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