Xyris tennesseensis
Encyclopedia
Xyris tennesseensis is a rare species of flowering plant in the family Xyridaceae
known by the common name Tennessee yellow-eyed grass. It is native to a small section of the Southeastern United States, where it is known from the states of Alabama
, Georgia
, and Tennessee
. It is threatened by the loss and degradation of its habitat. It is a federally listed endangered species
of the United States.
This is a perennial herb growing 30 to 70 cm (11.8 to 27.6 in) tall. The branching stem is bulbous and fleshy at the base. The leaves are long and narrow and originate at the swollen stem base. They are up to 45 centimeters long and not more than a centimeter wide. They are flat but sometimes twisted, and green in color with reddish or pink bases. The inflorescence
at the tip of the stem is a cone-like spike covered in tough brown scales. The flowers within are pale yellow in color. Each spike generally produces one flower per day, or sometimes two. The flower opens for a short time in the late morning and closes by mid-afternoon. Blooming occurs in August and September. The plants are pollinated
by insects, especially the sweat bee
Lasioglossum zephyrum
, which has been observed opening the buds to remove pollen before the flower opens, as to ensure it has first and exclusive access to the pollen.
This plant grows in open areas in wet habitat types such as streambanks, seeps
, fen
s, and wet meadows. The soils are thin and cover calcareous
rock. The plant grows in neutral to basic soils
, unlike other Xyris
species, which usually occur in acidic soils.
There are 16 to 25 populations of the plant in three US states. Some have been recently extirpated
, others are declining, and several others are in danger of destruction. Threats to the species include habitat destruction during timber
operations, including clearcutting
. Timber companies own much of the land occupied by the plant in Tennessee. Removal of stands of trees causes the soil to dry, making it inhospitable for this wetland endemic plant. Road construction and maintenance, including herbicide
application, is a threat.
The plant requires open, sunny habitat for germination
and growth, and it is threatened by the encroachment of large and woody vegetation in some areas. Proper land management
includes the clearing of brush and the removal of exotic plant species
such as Nepal grass
(Microstegium vimineum).
Xyridaceae
Xyridaceae is the botanical name of a family of flowering plants. Such a family has been recognized by many taxonomists and is known as the Yellow-eyed-grass Family....
known by the common name Tennessee yellow-eyed grass. It is native to a small section of the Southeastern United States, where it is known from the states of Alabama
Alabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
, Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
, and Tennessee
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
. It is threatened by the loss and degradation of its habitat. 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...
of the United States.
This is a perennial herb growing 30 to 70 cm (11.8 to 27.6 in) tall. The branching stem is bulbous and fleshy at the base. The leaves are long and narrow and originate at the swollen stem base. They are up to 45 centimeters long and not more than a centimeter wide. They are flat but sometimes twisted, and green in color with reddish or pink bases. The inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
at the tip of the stem is a cone-like spike covered in tough brown scales. The flowers within are pale yellow in color. Each spike generally produces one flower per day, or sometimes two. The flower opens for a short time in the late morning and closes by mid-afternoon. Blooming occurs in August and September. The plants are 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...
by insects, especially the sweat bee
Sweat bee
Sweat bee is the common name for any bees that are attracted to the salt in human sweat. In its strict application, the name refers to members of the Halictidae, a large family of bees that are common in most of the world except Australia and Southeast Asia, where they are only a minor faunistic...
Lasioglossum zephyrum
Lasioglossum zephyrum
Lasioglossum zephyrum is a sweat bee of the family Halictidae, found in the U.S. and Canada. It is known to be a somewhat antisocial species, and it has been shown to have a tendency to remain solitary. The species nests in underground burrows...
, which has been observed opening the buds to remove pollen before the flower opens, as to ensure it has first and exclusive access to the pollen.
This plant grows in open areas in wet habitat types such as streambanks, seeps
Seep (hydrology)
A Seep is a moist or wet place where water, usually groundwater, reaches the earth's surface from an underground aquifer.-Description:Seeps are usually not of sufficient volume to be flowing beyond their above-ground location. They are part of the limnology-geomorphology system...
, fen
Fen
A fen is a type of wetland fed by mineral-rich surface water or groundwater. Fens are characterised by their water chemistry, which is neutral or alkaline, with relatively high dissolved mineral levels but few other plant nutrients...
s, and wet meadows. The soils are thin and cover calcareous
Calcareous
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
rock. The plant grows in neutral to basic soils
Alkali soils
Alkali, or alkaline, soils are clay soils with high pH , a poor soil structure and a low infiltration capacity. Often they have a hard calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable physico-chemical properties mainly to the dominating presence of sodium carbonate...
, unlike other Xyris
Xyris
Xyris is the botanical name of a genus of flowering plants in the Yellow-eyed-grass family. The genus counts over two hundred fifty species, with the center of distribution in the Guianas....
species, which usually occur in acidic soils.
There are 16 to 25 populations of the plant in three US states. Some have been recently extirpated
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...
, others are declining, and several others are in danger of destruction. Threats to the species include habitat destruction during timber
Lumber
Lumber or timber is wood in any of its stages from felling through readiness for use as structural material for construction, or wood pulp for paper production....
operations, including clearcutting
Clearcutting
Clearcutting, or clearfelling, is a controversial forestry/logging practice in which most or all trees in an area are uniformly cut down. Clearcutting, along with shelterwood and seed tree harvests, is used by foresters to create certain types of forest ecosystems and to promote select species that...
. Timber companies own much of the land occupied by the plant in Tennessee. Removal of stands of trees causes the soil to dry, making it inhospitable for this wetland endemic plant. Road construction and maintenance, including herbicide
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...
application, is a threat.
The plant requires open, sunny habitat for germination
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...
and growth, and it is threatened by the encroachment of large and woody vegetation in some areas. Proper land management
Land management
Land management is the process of managing the use and development of land resources. Land resources are used for a variety of purposes which may include organic agriculture, reforestation, water resource management and eco-tourism projects.-See also:*Sustainable land management*Acreage...
includes the clearing of brush and the removal of exotic plant species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
such as Nepal grass
Microstegium vimineum
Microstegium vimineum, commonly known as Japanese stiltgrass or Nepalese browntop, is an annual grass that is common in a wide variety of habitats and is well adapted to low light levels.-Geographic range:...
(Microstegium vimineum).