|Photo by Shirley Denton (Copyrighted, use by photographer’s permission only), Atlas of Florida Vascular Plants|
|Division:||Magnoliophyta - Flowering plants|
|Class:||Magnoliopsida - Dicotyledons|
|Family:||Lamiaceae ⁄ Labiatae|
|Natural range of Dicerandra frutescens from USDA NRCS Plants Database.|
Common names: Scrub balm; Lloyd's mint
D. frutescens is a short-lived perennial, suffruticose species with a shallow tap root. There are two types of shoots: one is leafy and perennial, the other is flowering and annual. Species of Dicerandra contain essential oils and terpenoid mixtures that gives each species an unique odor (McCormick et al. 1993).
It can be distinguished from D. christmanii, another scrub mint found narrowly distributed along the Lake Wales Ridge, by having a minty aroma, longer leaves, and deep purple anthers.
Distribution is limited to the excessively yellow drained sand of the southern portion of the Lake Wales Ridge.
The Dicerandra genera is endemic to the longleaf pine range from southeastern Virginia to central Florida and west to southeast Texas.
D. frutescens occupies a small range in the southern portion of the Lake Wales ridge in xerophytic scrub oak communities on excessively drained yellow sands. Specific sand types include Astatula, Paola and Orsino. It often can be seen growing in gaps due to the high soil water availability, light levels, and low leaf litter accumulation (Weedley et al. 2007). Populations have been observed in disked areas such as fire lanes. Associated species include Lyonia ferruginea, Persea humilis, Carya floridana and Quercus laevis.
The flowers of D. frutescens are perfect and reproduce without crossing and are self compatible (Evans et al. 2003). The upper lip of the flower is marked internally with a purple trellis pattern of lines and dots, the lower lip is maculate with larger spots from lobe bases to the base of the lip. It has two pairs of stamen, with one pair being slightly longer and spurred anthers for insect pollination (Kral 1983). Flowers generally occur through August, with fruits present in September through winter.
Seed dispersal mechanisms are unclear.
Seed bank and germination
In a pyrogenic habitat such as the scrub habitat, it is predicted that endemic species show a positive germination response to smoke exposure. Populations of D. frutescens have been observed to flourish shortly after fire; however, smoke has been observed to not stimulate seed germination. This phenomenon could be due to germination from a persistent soil seed bank. Scrub fires have a tendency to be patchy and some reproductive individuals might avoid the fire, these survivors may be the reason populations flourish shortly after fire instead of a persistent seed bank.
The xerophytic scrubs of the Lake Wales Ridge rely on fire to maintain species composition and health. Optimum fire return interval for reducing extinction risk for D. frutescens is 6 to 12 years (Menges 2006). With fire suppression, there is a negative effect on fecundity and recruitment; however, there is a positive effect on seedling survival (Evans et al. 2010). There is a loss of medium and large flowering plants with fire suppression. D. frutescens is often found in open gaps; with an increase in time since fire, there is a decrease in the amount of gaps found in the scrub habitat. This causes a decrease in soil moisture availability and sunlight, along with an accumulation of litter, which can prove unfavorable conditions (Evans et al. 2010). Increasing the time since fire also suppresses flowering, either by increasing the chances of the individual changing from a reproductive state to the vegetative state, or by decreasing the chances an individuals will change from the vegetative state to a reproductive state (Evans et al. 2008).
If above ground tissue is removed by disturbances such as burning and clipping, the individual will die. This suggest that the heat of fire does not necessarily kill the individual; however, tissue removal alone is sufficient for mortality (Menges 1992).
Scrub fires have a tendency to be patchy, causing some individuals to be unaffected by fire, these survivors may be important in recolonizing site by seed dispersal (Menges 1992).
It has spurred anthers that require triggering by insects to release and disperse the pollen. It is mainly pollinated by bee-flies (Exoprosopa fasciata) (Evans et al. 2003). Pollinators have been observed to visit flowers in the sun more than flowers occurring in the shade (Deyrup and Menges 1997). Reproduction has been shown to have a positive correlation with population size and density (Evans et al. 2003). Dicerandra frutescens was observed at the Archbold Biological Station to host bees from the Apidae family such as Apis mellifera, Bombus impatiens and B. pennsylvanicus, sweat bees from the Halictidae family such as Augochlorella aurata and Lasioglossum placidensis, and leafcutting bees such as Megachile petulans (family Megachilidae).
Herbivory and toxicology
In order to protect itself from herbivory, D. frutescens has essential oils and terpenoid mixtures (McCormick et al. 1993). Cut leaves have been shown to repel ants. Only caterpillars of Pyralid moths are known to feed on this species (Eisner et al. 1990). Seed predators include Cynoides ciliates ssp. orientis (Evans 2004).
Conservation, cultivation, and restoration
D. frutescens is an endangered species that is endemic to a narrow range in the southern extent of the Lake Wales Ridge. Much of this area is being converted to agriculture and residential communities, limiting the ideal conditions for D. frutescens to grow. Many of the populations occur on unprotected private land that is fire suppressed.
FNAI rank: G1/S1. Currently is under cultivation at the Center for Plant Conservation as part of the permanent rare plant collection at Bok Tower Gardens, Lake Wales, Florida. Archbold Biological Station is conducting research on breeding, pollinators, demographic patterns and genetic variability.
References and notes
Deyrup, M.A. and N.D. 2015. Database of observations of Hymenoptera visitations to flowers of plants on Archbold Biological Station, Florida, USA.
Deyrup, M., and E.S. Menges. 1997. Pollination ecology of the rare scrub mint Dicerandra frutescens (Lamiaceae). Fla. Sci. 60:143-157.
Eisner, T., D. McCormick, M. Sakaino, M. Eisner, S.R. Smedley, D.J. Aneshansley, M. Deyrup, R.L. Myers, and J. Meinwald. 1990. Chemical defense of a rare mint plant. Chemoecology 1 (1990):30-37.
Evans, M. E. K., E. S. Menges, et al. (2004). "Mating systems and limits to seed production in two Dicerandra mints endemic to Florida scrub." Biodiversity and Conservation 13(10): 1819-1832.
Evans, Margaret E. K., Kent E. Holsinger, and Eric S. Menges. “Fire, Vital Rates, and Population Viability: A Hierarchical Bayesian Analysis of the Endangered Florida Scrub Mint”. Ecological Monographs 80.4 (2010): 627–649.
Huck, R.B. 1981. Dicerandra cornutissima, a new woody labiate from Florida. Phytologia 47:313-315.
McCormick, K.D., M. Deyrup, E.S. Menges, S.R. Wallace, J. Meinwald, and T. Eisner. 1993. Relevance of chemistry to conservation of isolated populations: The case of volatile leaf components of Dicerandra mints. Proceedings of the National Academy of Science, volume 90, pp. 7701-7705.
U.S. Fish and Wildlife Service. 1987. Recovery plan for three Florida mints. U.S. Fish and Wildlife Service; Atlanta, Georgia.
- Huck, R.B., W.S. Judd, W.M. Whitten, J.D. Skean Jr., R.P. Wunderlin, K.R. Delaney. 1989. A new Dicerandra (Labiatae) from the Lake Wales Ridge of Florida, with a cladistic analysis and discussion of endemism. Systematic Botany 14(2):197-213.
- Menges, E. S. 1992. Habitat preferences and response to disturbance for Dicerandra frutescens, a Lake Wales Ridge (Florida) endemic plant. Bulletin of the Torrey Botanical Club 119(3): 308-313.
- [FWS]Accessed: December 9, 2015
- Sorrie, B. A. and A. S. Weakley 2001. Coastal Plain valcular plant endemics: Phytogeographic patterns. Castanea 66: 50-82.
- Florida State University Robert K. Godfrey Herbarium database. URL: http://herbarium.bio.fsu.edu. Last accessed: October 2015. Collectors: P. Alcorn, Steven P. Christman, Robert K. Godfrey, Walter S. Judd, J.D. Skean. States and Counties: Florida: Highlands. Compiled by Tall Timbers Research Station and Land Conservancy.
- Menges, Eric S. et al.. “Microhabitat of the Narrow Florida Scrub Endemic Dicerandra Christmanii, with Comparisons to Its Congener D. Frutescens”. Journal of the Torrey Botanical Society 126.1 (1999): 24–31.
- Menges, Eric S.. “Demography of the Endemic Mint Dicerandra Frutescens in Florida Scrub: Ecological Archives E089-088”. Ecology 89.5 (2008): 1474–1474.
- Nelson, G. PanFlora: Plant data for the eastern United States with emphasis on the Southeastern Coastal Plains, Florida, and the Florida Panhandle. www.gilnelson.com/PanFlora/ Accessed: 19 MAY 2021
- Lindon, Heather Lynn, and Eric Menges. “Scientific Note: Effects of Smoke on Seed Germination of Twenty Species of Fire-prone Habitats in Florida”. Castanea 73.2 (2008): 106–110.
- Lang, N. L. 2011. Soil seed bank dynamics of southern Lake Wales Ridge sandhill communities. Archbold Biological Station, Venus, Florida,15 pg.
- Deyrup, M.A. and N.D. 2015. Database of observations of Hymenoptera visitations to flowers of plants on Archbold Biological Station, Florida, USA.
- [Center for Plant Conservation] Accessed: December 9, 2015
- [Archbold Biological Station]Accessed: December 7, 2015
- [FNAI]Accessed: December 7, 2015