Creeping St. John's-wort / Center For Plant Conservation
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Plant Profile

Creeping St. John's-wort (Hypericum adpressum)

Hypericum adpressum flowers close-up

 Photo Credit: Chase Mathey
  • Global Rank: G3 - Vulnerable
  • Legal Status: N/A
  • Family: Hypericaceae
  • State: AR, CT, DE, GA, IL, IN, KY, MA, MD, MI, MO, NC, NJ, NY, PA, RI, SC, TN, VA, WV
  • Nature Serve ID: 132006
  • Lifeform: Forb/herb
  • Date Inducted in National Collection: 11/07/2022
Description:

Hypericum adpressum is a medium-sized, rhizomatous or stoloniferous forb with erect, sparsely branching stems of 40 - 80 cm in length. Stems are usually slender however; prolonged periods in flooded conditions can cause the stem to become thickened and spongy (Edgin and Mankowski 2013). H. adpressum leaves are narrowly elliptic to lanceolate, pinnately veined, and 3.5 - 7 cm long. The leaves are arranged in whorls with the upper side of the leaf often shiny in appearance. It has 1 - 2 cm wide yellow to orange flowers grown in terminal clusters with revolute sepals. The annual vigor and growth of populations in the wild can vary greatly depending on the hydrologic conditions during the growing season (Enser 2000).

Where is Creeping St. John's-wort (Hypericum adpressum) located in the wild?

Habitat:

This species prefers natural depressions in seasonally saturated freshwater wetlands where it thrives in the area between low and high water. Hypericum adpressum occur on the acidic sand, gravel, or peaty soils of freshwater pond shorelines, swales, wet meadows, marshes, depressions, as well as some anthropogenic habitats like wet railroad & roadside ditches, and the margins of cranberry bogs (Sorrie 1987). This species requires full sun. Although H. adpressum grows best in habitats with fluctuating hydrology, it can survive in areas with more permanent inundation (Edgin and Mankowski 2013).

Distribution:

Hypericum adpressum has a scattered distribution that is confined to isolated wetlands throughout the eastern U.S. The core of its range runs along the Atlantic coastal plain from Georgia to Massachusetts. The number of wild populations is spotty at the southern end of the coastal plain and becomes more abundant from New Jersey and north. There are a number of disjunct populations found west of the Appalachian Mountains, the majority of which are located in northeastern Illinois. In 2006, a population of H. adpressum was discovered in Arkansas (Witsell 2007). In total, there are approximately 75-80 extant occurrences throughout the range and an additional 65 occurrences that are believed to be extirpated. The biggest threat to this rare species is the alteration of hydrology in suitable wetland habitat (Edgin and Mankowski 2013). Only a third of all the known occurrences are located within any sort of managed or protected area.

States & Provinces:

Creeping St. John's-wort can historically be found in Arkansas, Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Michigan, Missouri, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, West Virginia

Which CPC Partners conserve Creeping St. John's-wort (Hypericum adpressum)?

  • Missouri Botanical Garden

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    Gold Sponsor

    Edward K. Love Foundation

    Conservation Actions
    Assigned 11/07/22
    • CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.

    Conservation Actions

    Bradley Delfeld
    • 01/15/2025
      • Propagation Research Orthodox Seed Banking

    In 2023, Missouri Botanical Garden seed bank staff performed a 5-year viability check on the Hypericum adpressum in cold storage. Of the 23 seeds sown in the germination test, 0 germinated, 14 grew moldy, and 9 were found to be empty seeds (0% viability).

    Bradley Delfeld
    • 01/15/2025
      • Propagation Research Orthodox Seed Banking

    In 2021, Missouri Botanical Garden seed bank staff performed a 3-year viability check on the Hypericum adpressum seeds in cold storage. This included a germination test as well as X-ray imaging of the seeds to determine if it is empty or filled. In total, 36 seeds were X-rayed and only 8 appeared to be filled (22.22% filled). In the germination test, 30 seeds were sown onto agar, and only 4 germinated (22.22% viable - 12 were found to be empty seeds and thus excluded from the viability calculation).

    Bradley Delfeld
    • 01/15/2025
      • Seed Collection Orthodox Seed Banking

    The Missouri Botanical Garden holds one accession of approximately 2294 seeds in its seed bank. The seed was collected in Scott County, Missouri on October 4, 2017.

    Tina Stanley
    • 11/07/2022
      • Orthodox Seed Banking

    Missouri Botanical Garden holds this species in conservation seed collection.

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    Nomenclature
    Taxon Hypericum adpressum
    Authority William Paul Crillon Barton (1818)
    Family Hypericaceae
    CPC Number 449697
    ITIS 21424
    USDA HYAD
    Duration Perennial
    Common Names Creeping St. Johnswort | Creeping St. John's-wort
    Associated Scientific Names Hypericum adpressum
    Distribution Hypericum adpressum has a scattered distribution that is confined to isolated wetlands throughout the eastern U.S. The core of its range runs along the Atlantic coastal plain from Georgia to Massachusetts. The number of wild populations is spotty at the southern end of the coastal plain and becomes more abundant from New Jersey and north. There are a number of disjunct populations found west of the Appalachian Mountains, the majority of which are located in northeastern Illinois. In 2006, a population of H. adpressum was discovered in Arkansas (Witsell 2007). In total, there are approximately 75-80 extant occurrences throughout the range and an additional 65 occurrences that are believed to be extirpated. The biggest threat to this rare species is the alteration of hydrology in suitable wetland habitat (Edgin and Mankowski 2013). Only a third of all the known occurrences are located within any sort of managed or protected area.
    State Rank
    State State Rank
    Arkansas S1
    Connecticut SH
    Delaware S2
    Georgia S1
    Illinois S1
    Indiana S1
    Kentucky SNR
    Maryland S1
    Massachusetts S2
    Michigan S1
    Missouri S1
    New Jersey S1
    New York S2
    North Carolina SH
    Pennsylvania SX
    Rhode Island S2
    South Carolina S2
    Tennessee S1
    Virginia S1
    West Virginia SH
    Ecological Relationships

    Photos

    Hypericum adpressum flowers close-up

    Photo Credit: Chase Mathey

    Hypericum adpressum in flower in habitat.

    Photo Credit: Kelly Omand

    Hypericum adpressum in habitat.

    Photo Credit: Kelly Omand

    Hypericum adpressum in flower in Michigan.

    Photo Credit: Nate Martineau

    Hypericum adpressum Capsules

    Photo Credit: Meg Engelhardt

    Hypericum adpressum Seeds

    Photo Credit: Meg Engelhardt

    Bisected Hypericum adpressum Seeds- one empty and one filled

    Photo Credit: Katie Pittman

    X-ray Image of Hypericum adpressum Seeds

    Photo Credit: Katie Pittman

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