|Photo by Keith Bradley, Atlas of Florida Vascular Plants|
|Division:||Magnoliophyta - Flowering plants|
|Class:||Magnoliopsida - Dicotyledons|
|Family:||Clusiaceae ⁄ Guttiferae|
| Hypericum tenuifolium|
|Natural range of Hypericum tenuifolium from USDA NRCS Plants Database.|
Common name: Atlantic St. Johnswort
Synonyms: Hypericum reductum (Svenson) W.P. Adams; H. aspalathoides Willdenow
H. tenuifolium is a short lived perennial herb that can reach heights of 12 to 18 inches. Stems are reddish brown and are covered with short needle-like shiny deep green leaves. The flowers have 5 yellow petals, 5 persistent sepals, a superior ovary, and are bisexual and radially symmetrical. A distinctive characteristic of this species is a long seed capsule, ranging from 6 to 9 mmm long.
“Usually glabrous herbs or shrubs. Leaves usually punctate, simple, opposite, entire, usually sessile or subsessile, exstipulate. Inflorescence basically cymose; flowers perfect, regular, bracteates, subsessile or short-pedicellate, sepals 2, 4, or 5, persistent; petals 4 or 5, usually marcescent, yellow or pink; stamens 5-numerous, separate or connate basally forming 3-5 clusters or fascicles, filaments usually persistent; carpels 2-5, stigmas and styles separate or fused, ovary superior, 1-locular or partly or wholly 2-5 locular, placentation axile or parietal. Capsules basically ovoid, longitudinally dehiscent, styles usually persistent; seeds numerous, lustrous, areolate, cylindric or oblong. In general our species form a polymorphic complex with many intergrading taxa.” 
"Decumbent, matted shrub, 1-5 dm tall, stems usually angled. Leaves linear-subulate, the largest 5-13 mm long, 0.5-1 mm wide, acute, slightly revolute, base notched, sessile. Cymules or dichasia terminal and axillary, or flower solitary, axillary. Sepals 5, similar to leaves, usually less than4.5 mm long; petals 5, 4-10 mm long; styles 3, united or usually separate in fruit, 0.8-3 mm long, ovary 3-locular. Capsules subcylindric, 6-9 mm long, 1.5-2 mm broad; seeds blackish, ca. 0.5 mm long." 
This species is found in dry, sandy, open sites with good drainage such as sandy woods, dunes and dune hollows, lowland and coastal areas. It is drought tolerant, however does not favor well in soils that remain wet for extended periods. Associated species include Polygonella polygama, Pinus palustris and Paronychia chartacea.
The following Hymenoptera families and species were observed visiting flowers of Hypericum tenuifolium at Archbold Biological Station: 
Apidae: Apis mellifera, Bombus griseocollis, B. impatiens
Colletidae: Colletes distinctus, C. productus, C. sp. A, Hylaeus confluens
Halictidae: Augochlorella aurata, A. gratiosa, Augochloropsis anonyma, A. metallica, A. sumptuosa, Lasioglossum miniatulus, L. nymphalis, L. placidensis, L. tamiamensis
Megachilidae: Anthidiellum perplexum, Dianthidium floridiense, Megachile albitarsis, M. brevis pseudobrevis, M. rugifrons
Conservation and management
Cultivation and restoration
References and notes
- []UGA Extension Accessed: January 6, 2016
- [] Name that Plant. Accessed: January 6, 2016
- [] Accessed: January 6, 2016
- Radford, Albert E., Harry E. Ahles, and C. Ritchie Bell. Manual of the Vascular Flora of the Carolinas. 1964, 1968. The University of North Carolina Press. 709-712. Print.
- [] Hypericum online. Accessed: January 6, 2016
- Florida State University Robert K. Godfrey Herbarium database. URL: http://herbarium.bio.fsu.edu. Last accessed: October 2015. Collectors: Loran C. Anderson, Wilson Baker, Ann Johnson. States and Counties: Florida: Bay. Compiled by Tall Timbers Research Station and Land Conservancy.
- Deyrup, M.A. and N.D. 2015. Database of observations of Hymenoptera visitations to flowers of plants on Archbold Biological Station, Florida, USA.