- Scientific name: Hypericum adpressum Barton
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
- Threatened (MA Endangered Species Act)
Description
Creeping St. John's-wort, Hypericum adpressum, is a stoloniferous (spreading by runners) herbaceous perennial belonging to the St. John's-wort family (Hypericaceae). It produces erect, sparsely branched stems 30-80 cm (12-30 in) tall which are terminated by open heads (cymes) of many bright yellow flowers. Each flower is 1.5-2 cm (0.6-0.8 in) wide with five petals surrounding a prominent cluster of 20 to 100 yellow stamens. The glossy green leaves are variably linear to oblong-elliptic, 3-6 cm (1.2-2.4 in) long, tapered at both ends, and distinguished by rolled-under (revolute) margins. They are arranged in whorls of two or three leaves which often support several bundles of smaller leaves. The stem bases have a tendency to become thickened and spongy when the plants are submerged for extended periods. The fruit is an oval- or globe-shaped capsule with a long, narrow tip.
Two related species closely resemble creeping St. John's-wort. Greater St. John's-wort (H. majus) differs by its smaller flowers, fewer stamens, and a narrower capsule. Pale St. John's-wort (H. ellipticum) has smaller, more elliptical leaves without revolute margins. Also sharing the same habitats are the Canadian, marsh, and northern dwarf St. John’s-worts, (Hypericum canadense, Triadenum virginicum, and H. boreale). Each differs sufficiently from creeping St. John's-wort to be easily distinguished without detailed examination.
Life cycle and behavior
This is a perennial species. Flowering occurs from late July to early September.
Population status
This species is listed as threatened under the Massachusetts Endangered Species Act. There are 7 populations verified since 1999 of this species which occur in Barnstable and Nantucket Counties. There are an additional 5 populations that have not been relocated in the past 25 years.
Distribution and abundance
Creeping St. John's-wort is primarily a southern and midwestern species that reaches its northernmost range limit in Massachusetts. It is locally distributed from eastern Massachusetts south along the coastal plain to Georgia, and inland to Tennessee, Kentucky, Indiana and Illinois. It is considered a rare species in every state where it is known to occur. In New England, creeping St. John's-wort is possibly extirpated from Connecticut and imperiled in Massachusetts and Rhode Island. It is not known to have occurred in Maine, New Hampshire or Vermont. It is considered a globally rare species due to only 75 to 80 widely scattered populations in the world (NatureServe 2025).
Distribution in Massachusetts. 2000-2025. Based on records in the Natural Heritage Database.
Habitat
In Massachusetts, creeping St. John's-wort is a coastal plain species, primarily found on the shores of freshwater ponds and "pondlets" that are permanent bodies of water, but which undergo pronounced seasonal fluctuations in water level. It also occurs in two other atypical habitats, a seasonally wet dirt road near a shrubby wetland, and at the edge of a cranberry bog. All of these sites are open, relatively flat, and free of tree and shrub competition. Composed of nutrient-poor, sandy-peaty soils, they are subject to intervals of drought alternating with flooding and saturation. Creeping St. John's-wort has adapted to these stresses by synchronizing its growth and flowering periods with the changing water levels. The predominant vegetation of grasses, sedges and herbs includes common shore species such as: slender-leaved flat-topped goldenrod (Euthamia caroliniana, formerly E. tenuifolia), meadow beauty (Rhexia virginianum), brown beak-rush (Rhynchospora capitellata), and several common rushes (Juncus spp.). In favorable situations, creeping St. John's-wort may be a dominant species, growing in large stands of several hundred or more plants. In spite of this, it is unpredictable in its occurrence, and absent from much apparently suitable habitat, indicating that other unknown factors must influence its distribution.
Healthy habitats are vital for supporting native wildlife and plants. Explore habitats and learn about conservation and restoration in Massachusetts.
Threats
The threats to creeping St. John’s-wort are similar to those to the coastal plain habitat where it occurs. With sea level rise, there is an expected coastal plain pond water level rise as well (Staudinger et al. 2024). With higher water levels in the ponds, the species may get flooded and the stems that aren’t flooded may be pushed into shaded forested edges where it can grow but not thrive. Other threats include trampling by people as it grows on or near the open areas of beaches on coastal plain ponds, invasive species, particularly common reed (Phragmites australis), and browsing by deer and other mammals (rabbits, etc.).
Conservation
Regular monitoring of creeping St. John’s-wort is important to maintain protection of this species in its habitats. Its population numbers sometimes fluctuate wildly and should be re-surveyed within a year if not found at a location. The best time to survey for the species is when it is flowering from late July into early September.
The exact ecological needs of creeping St. John’s-wort are not fully understood. Management might include reducing deer and other browsing animal populations near populations of creeping St. John’s-wort, cutting vegetation along southern shorelines to allow more light to reach plants growing higher on the shore, and removal of invasive plant species. Signage at beaches and boat launches to prevent trampling of plants may be helpful as well. . All active management of rare plant populations (including invasive species removal) is subject to review under the Massachusetts Endangered Species Act and should be planned in close consultation with the MassWildlife's Natural Heritage & Endangered Species Program.
Research is needed to determine whether this plant can be grown in a nursery or garden setting for purposes of reintroductions. Questions about seed germination and seed storage over winter will need to be answered. As sea-level rise may destroy current populations, this strategy for reintroductions could prove useful to long-term conservation of this species.
References
Gleason, Henry A., and Arthur Cronquist. Manual of Vascular Plants of Northeastern United States
and Adjacent Canada, Second Edition. Bronx, NY: The New York Botanical Garden, 1991.
Haines, A. 2011. Flora Novae Angliae – a Manual for the Identification of Native and Naturalized Higher Vascular Plants of New England. New England Wildflower Society, Yale Univ. Press, New Haven, CT.
Native Plant Trust. 2014. NORM Phenology Information.
NatureServe. 2025. NatureServe Network Biodiversity Location Data accessed through NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org/. Accessed: 5/23/2025.
POWO (2025). Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; https://powo.science.kew.org/ Accessed: 3/4/2025.
Staudinger, M.D., A.V. Karmalkar, K. Terwilliger, K. Burgio, A. Lubeck, H. Higgins, T. Rice, T.L. Morelli, A. D'Amato. 2024. A regional synthesis of climate data to inform the 2025 State Wildlife Action Plans in the Northeast U.S. DOI Northeast Climate Adaptation Science Center Cooperator Report. 406 p. https://doi.org/10.21429/t352-9q86
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| Date published: | April 29, 2025 |
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