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Slender St. John's-wort (Hypericum mutilum)

Life history

Species overview

Slender St. John's-wort (Hypericum mutilum), a Wisconsin Special Concern plant, is found in mesic meadows, marshes, and along streams. Blooming occurs from July through September. The optimal identification period for this species is mid summer through fall.



  • Distinguishing characteristics: Erect stem with much upper branching, up to .8 m tall. Of other similar Hypericums, Northern St. John's-wort (H. boreale) has wider bracts of .5 to 2 mm wide, Larger Canada St. John's-wort (H. majus) has 5-nerved lanceolate leaves, and Canadian St. John's-wort (H. canadense) has linear-oblanceolate to lanceolate leaves with 1 to 3 nerves.
  • Flower characteristics: Flowers yellow and 5-parted in a branched cluster, with very reduced bracts up to .2 mm wide. Individual flowers are 3 to 4 mm wide.
  • Fruit characteristics: Dark purple, ellipsoid capsule 2.5 - 4 mm in length.
  • Leaf characteristics: Leaves are stalkless, oval to elliptical and rounded on both ends and 1 to 4 cm long.


  • Blooming phenology: July through September
  • Fruiting phenology:
  • Optimum time to identify: The optimal identification period for this species is mid summer through fall


  • Growth form: Herb or shrub
  • Vegetative reproduction:
  • Life cycle: Annual or Perennial
  • Comments: This plant can be propogated via sprigs.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - state and federal - and the rank (S and G Ranks) for Slender St. John's-wort (Hypericum mutilum). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.

Documented locations of Hypericum mutilum in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusSC
Federal Status in Wisconsinnone
State RankS2
Global RankG5
Tracked by NHIY

Habitats and landscapes

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

General habitat information

  • Habitat description: Found in mesic meadows, marshes, and along streams.
  • Soils: Acidic, rocky or sandy soils.

Natural communities

This table lists the natural communities that are associated with Slender St. John's-wort. Scores for natural community associations are: "significant" association (score=3), "moderate association" (score=2) or the species can be present but is only weakly associated with the community (score=1).

Ecological landscapes

This table lists the ecological landscape association scores for Slender St. John's-wort. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Map of the Ecological Landscapes of Wisconsin.

Ecological landscape score
Central Sand Plains 1
Western Coulee and Ridges 3

Species guidance

The Endangered Resources Program has developed avoidance measures and management guidelines for plants on the Natural Heritage Working List. These are a work in progress, and we welcome your suggestions and feedback. Sources used in developing this information can be found here.

Avoidance measures

These are specific actions designed to avoid "take" (mortality) of this species.

  • No avoidance measures have been developed for this species.

Management guidance

Management guidelines are additional considerations that may help maintain or enhance habitat for this species

  • No guidance has been developed for this species.


Slender St. John's-wort Photo.

Photo © Merel R. Black.

Support for Wisconsin's rare plant information has been provided by the Division of Forestry, the Endangered Resources Fund and the Wisconsin Rare Plant Preservation Fund. To donate, visit the Natural Resources Foundation of Wisconsin [exit DNR].

Last revised: Wednesday, May 05, 2021
Southwest Savanna Southern Lake Michigan Coastal Western Coulees and Ridges Southeast Glacial Plains Central Sand Hills Central Lake Michigan Coastal Central Sand Plains Northern Lake Michigan Coastal Northern Lake Michigan Coastal Northeast Sands Western Prairie North Central Forest Northern Highlands Northwest Lowlands Northwest Sands Northwest Lowlands Superior Coastal Plains Forest Transition