Dicerandra christmanii
Encyclopedia
Dicerandra christmanii is a rare species of flowering plant in the mint family
known by the common names Garrett's mint, yellow scrub balm, and Lake Wales balm. It is endemic to Highlands County, Florida
, in the United States, where it is known from only four sites on the Lake Wales Ridge
. All are contained within a tract of land measuring 6 kilometers by 3 kilometers. The plant is steadily declining due to the destruction and degradation of its habitat, and only one of the four occurrences is on protected land. It is a federally listed endangered species
.
The plant was first collected in 1948 by Ray Garrett. Over the years it was included within the description of its close relative, Dicerandra frutescens
. In 1989 it was reexamined and named as a new species on the basis of the color of its anthers
, its scent and certain related chemical compounds in the herbage, and the length of its leaves. D. christmanii has white or cream-colored flowers with yellow anthers, a menthol
scent, and shorter leaves, while D. frutescens has cream flowers that fade to white, and purple or white anthers. The two are otherwise quite similar in appearance. D. christmanii is an aromatic shrub
growing up to 1.3 feet tall. The squared, ridged stem and oppositely arranged leaves have many oil glands. Blooming occurs in summer and fall. Flowers occur singly or in whorls of three. Each is white to cream in color with purple spotting on the lobed lips. The yellow-anthered stamens protrude from the mouth of the corolla and bear white pollen
. The anthers have spurs that trigger the release of pollen, a trait common to genus Dicerandra. The plant is pollinated
most often by Exprosopa fasciata, a species of bee-fly
.
This plant is one of many that is found only on Lake Wales Ridge, an area of very high endemism. The habitat is yellow-sand Florida scrub
dominated by sand pines (Pinus clausa), several species of oak
, and scrub hickory (Carya floridana). It does not occur together with D. frutescens, but slightly to the north of its relative. The habitat is highly fragmented
, with land in the area converted to citrus groves
. Remaining parts are degraded, the wildfire
-adapted habitat having been overgrown with dense vegetation in an era of fire suppression. The mint only grows in open areas in the canopy, space which is rare today as the larger and woody vegetation succeeds
. Fire is also required to clear out leaf litter in the understory
. Furthermore, plants of this species in open habitat are more likely to be visited by pollinator
s than plants under overgrown canopy.
Besides outright habitat loss and lack of a natural fire regime
, threats to the species include drought
and the invasive weed
cogon grass (Imperata cylindrica). The plant has a limited ability to disperse its seeds
, and this is reduced more by the fragmentation of the habitat. Off-road vehicle
s and trash dumping
may affect the area.
Because D. frutescens was already on the endangered species list, D. christmanii was given that status when it was separated and named a new species. It is considered "one of the most critically endangered plant species on the Lake Wales Ridge," among many endangered species.
Lamiaceae
The mints, taxonomically known as Lamiaceae or Labiatae, are a family of flowering plants. They have traditionally been considered closely related to Verbenaceae, but in the 1990s, phylogenetic studies suggested that many genera classified in Verbenaceae belong instead in Lamiaceae...
known by the common names Garrett's mint, yellow scrub balm, and Lake Wales balm. It is endemic to Highlands County, Florida
Highlands County, Florida
Highlands County is a county located in the U.S. state of Florida. The U.S. Census Bureau 2006 estimate for the population was 97,346. Its county seat is Sebring, Florida. The county comprises the Sebring, Florida, Micropolitan Statistical Area.- History :...
, in the United States, where it is known from only four sites on the Lake Wales Ridge
Lake Wales Ridge
The Lake Wales Ridge is a low ridge running for about 150 miles south to north in Central Florida. The greater part of the ridge is in Highlands County and Polk County, but it extends north into Osceola, Orange and Lake Counties. It is named for the city of Lake Wales, roughly at the mid point of...
. All are contained within a tract of land measuring 6 kilometers by 3 kilometers. The plant is steadily declining due to the destruction and degradation of its habitat, and only one of the four occurrences is on protected land. It is a federally listed endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
.
The plant was first collected in 1948 by Ray Garrett. Over the years it was included within the description of its close relative, Dicerandra frutescens
Dicerandra frutescens
Dicerandra frutescens is a rare species of flowering plant in the mint family known by the common names scrub mint and scrub balm. It is endemic to Highlands County, Florida, where it is known only from the Lake Wales Ridge. Its habitat is quickly being lost as it is converted to residential and...
. In 1989 it was reexamined and named as a new species on the basis of the color of its anthers
Stamen
The stamen is the pollen producing reproductive organ of a flower...
, its scent and certain related chemical compounds in the herbage, and the length of its leaves. D. christmanii has white or cream-colored flowers with yellow anthers, a menthol
Menthol
Menthol is an organic compound made synthetically or obtained from peppermint or other mint oils. It is a waxy, crystalline substance, clear or white in color, which is solid at room temperature and melts slightly above. The main form of menthol occurring in nature is -menthol, which is assigned...
scent, and shorter leaves, while D. frutescens has cream flowers that fade to white, and purple or white anthers. The two are otherwise quite similar in appearance. D. christmanii is an aromatic shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
growing up to 1.3 feet tall. The squared, ridged stem and oppositely arranged leaves have many oil glands. Blooming occurs in summer and fall. Flowers occur singly or in whorls of three. Each is white to cream in color with purple spotting on the lobed lips. The yellow-anthered stamens protrude from the mouth of the corolla and bear white pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
. The anthers have spurs that trigger the release of pollen, a trait common to genus Dicerandra. The plant is pollinated
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
most often by Exprosopa fasciata, a species of bee-fly
Bombyliidae
Bombyliidae is a large family of flies with hundreds of genera, although their life cycles are not well known. Adults generally feed on nectar and pollen, thus are pollinators of flowers. They superficially resemble bees, thus are commonly called bee flies, and this may offer the adults some...
.
This plant is one of many that is found only on Lake Wales Ridge, an area of very high endemism. The habitat is yellow-sand Florida scrub
Florida scrub
Florida scrub is an endangered temperate coniferous forest ecoregion of the state of Florida in the United States. It is found on coastal and inland sand ridges and is characterized by a xeromorphic plant community dominated by shrubs and dwarf oaks. Scrub soils, a type of entisol, are derived...
dominated by sand pines (Pinus clausa), several species of oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
, and scrub hickory (Carya floridana). It does not occur together with D. frutescens, but slightly to the north of its relative. The habitat is highly fragmented
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...
, with land in the area converted to citrus groves
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
. Remaining parts are degraded, the wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
-adapted habitat having been overgrown with dense vegetation in an era of fire suppression. The mint only grows in open areas in the canopy, space which is rare today as the larger and woody vegetation succeeds
Ecological succession
Ecological succession, is the phenomenon or process by which a community progressively transforms itself until a stable community is formed. It is a fundamental concept in ecology, and refers to more or less predictable and orderly changes in the composition or structure of an ecological community...
. Fire is also required to clear out leaf litter in the understory
Understory
Understory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...
. Furthermore, plants of this species in open habitat are more likely to be visited by pollinator
Pollinator
A pollinator is the biotic agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain...
s than plants under overgrown canopy.
Besides outright habitat loss and lack of a natural fire regime
Fire regime
A fire regime is the pattern, frequency and intensity of the bushfires and wildfires that prevails in an area. It is an integral part of fire ecology, and renewal for certain types of ecosystems. If fires are too frequent, plants may be killed before they have matured, or before they have set...
, threats to the species include drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
and the invasive weed
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
cogon grass (Imperata cylindrica). The plant has a limited ability to disperse its seeds
Seed dispersal
Seed dispersal is the movement or transport of seeds away from the parent plant. Plants have limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors. Seeds can be dispersed away from the parent plant...
, and this is reduced more by the fragmentation of the habitat. Off-road vehicle
Off-road vehicle
An off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks...
s and trash dumping
Waste
Waste is unwanted or useless materials. In biology, waste is any of the many unwanted substances or toxins that are expelled from living organisms, metabolic waste; such as urea, sweat or feces. Litter is waste which has been disposed of improperly...
may affect the area.
Because D. frutescens was already on the endangered species list, D. christmanii was given that status when it was separated and named a new species. It is considered "one of the most critically endangered plant species on the Lake Wales Ridge," among many endangered species.