|Photo by Bruce Hansen, Atlas of Florida Vascular Plants|
|Division:||Magnoliophyta - Flowering plants|
|Class:||Magnoliopsida - Dicotyledons|
|Family:||Clusiaceae ⁄ Guttiferae|
| Hypericum edisonianum|
(Small) P. Adams & N. Robson
|Natural range of Hypericum edisonianum from USDA NRCS Plants Database.|
Common name: Arcadian St. Johnswort
Synonym: Ascyrum edisonianum Small USDA NRCS Plants Database
H. edisonianum is a multi-branched evergreen shrub that forms extensive thickets. The stems are thin and dark with silvery black bark, and are leafless except for the upper branches. Leaves are opposite, oval, and have abaxial glands. The flowers are composed of 4 yellow petals, 2 large sepals with pointed tips and rounded bases.
This species exhibits traits that are common to rare and geographically limited plant species such as: (a) heavy reliance on clonal propagation to maintain local stands (b) passive seed dispersal resulting in a near-parent seed shadow (c) limited numbers of genetically unique individuals in isolated seasonal pond habitat (d) self-incompatibility.
“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.” 
The range is limited to the scrubs of the central peninsular Florida in Highlands, Polk, Glades, DeSoto, and Collier counties.  Excessive drainage, agriculture, and urban development are locally eliminating the species. 
In the central peninsular counties of Florida, H. edisonianum has been found in ephemeral ponds, flatwood ponds, and wet swales in low pine-palmetto flats, cutthroat grass seeps, and along lake margins.  It tends to form dense thickets of ramets in poorly drained sandy sites that have a low pH, little organic matter, and low nutrient status, such as seasonal ponds.  Associated species include Andropogon brachystachyus, Ascyrum tetrapetalum, and Ascyrum hypericoides. Soils have been recorded as Paola-Basinger (Spodic Quartzipsamments). 
H. edisonianum is self-incompatible. The amount of flowers in anthesis within ramets are limited and independent of one another because individual flowers are short lived and flowering occurs throughout the year. Reproduces by seeds and clonal sprouting from underground rhizomes which is important for demography and genetic structure of populations. 
Seeds are a dark brown, pointed capsule. It exhibits passive seed dispersal resulting in a near-parent seed shadow. In wet areas, seeds sink and become embedded in sand near the parent unless moved by sheetflow during flooding or by wind during dry periods. 
H. edisonianum is found in pyrogenic scrubs of central peninsular Florida and rapidly regenerates ramets following fires (Abrahamson et al. 1984; Menges and Kohfeldt 1995). Fires and other disturbances can reduce competition and the effects of herbivory and diseases. 
The following Hymenoptera families and species were observed visiting flowers of Hypericum edisonianum at Archbold Biological Station: 
Apidae: Apis mellifera, Bombus impatiens, B. pennsylvanicus
Colletidae: Hylaeus confluens, H. schwarzi
Halictidae: Augochloropsis sumptuosa, Lasioglossum miniatulus, L. nymphalis, L. pectoralis, L. placidensis, L. puteulanum
Megachilidae: Anthidiellum perplexum, Megachile brevis pseudobrevis, M. mendica, M. petulans
Conservation and management
It is unable to withstand excessive landscape drainage, agricultural and human development.  Fire suppression can result in population loss. Allowing prescribed fires to burn into wetlands and maintaining the natural hydrology of flatwoods can help manage populations of H. edisonianum. Listed as G2/S2.
Cultivation and restoration
Flowers of Hypericum edisonianum
Photo by Bob Upcavage, Atlas of Florida Vascular Plants
References and notes
Abrahamson, W. G. (1984). "Species Responses to Fire on the Florida Lake Wales Ridge." American Journal of Botany 71(1): 35-43.Menges, E.S. and N. Kohfeldt. 1995. Life history strategies of Florida scrub plants in relation to fire. Bull. Torrey Bot. Club 122:282–297.
- []FNAI. Accessed: January 5, 2015
- Warren G. Abrahamson II and Sam P. Vander Kloet. "The Reproduction and Ecology of Hypericum edisonianum: An Endangered Florida Endemic" Castanea 79.3 (2014): 168-181. Available at: http://works.bepress.com/warren_abrahamson/153
- 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. Print.
- Ward, D.B. 1979. Rare and endangered biota of Florida, Volume 5. Plants. University Presses of Florida, Gainesville, Florida.
- Florida State University Robert K. Godfrey Herbarium database. URL: http://herbarium.bio.fsu.edu. Last accessed: October 2015. Collectors: W.P. Adams, Leonard J. Brass, Edwin L. Bridges, George R. Cooley, R.K. Godfrey, Colleen Hoy, Beverly Judd, Walter S. Judd, Steve L. Orzell, Grady W. Reinert, Joe Testasecca, Daniel B. Ward, Kenneth A. Wilson, Carroll E. Wood. States and Counties: Florida: Glades, Highlands. 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.