CPC Plant Profile: Tennessee Yellow-eyed-grass
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Plant Profile

Tennessee Yellow-eyed-grass (Xyris tennesseensis)

Flower heads Photo Credit: Mincy Moffett
Description
  • Global Rank: G2 - Imperiled
  • Legal Status: Federally Endangered
  • Family: Xyridaceae
  • State: AL, GA, TN
  • Nature Serve ID: 148370
  • Date Inducted in National Collection: 12/01/2021

Tennessee yellow-eyed grass (Xyris tennesseensis) is a perennial herb with a fleshy, bulbous base, usually occurring in small clumps. Leaves are 5 - 18 inches (14 - 45 cm) long, - ⅜ inch (0.5 - 1 cm) wide, erect, flat or slightly twisted with swollen, pink or purple leaf bases overlapping up to one-third the length of the blade. The flower stalk is 12 - 28 inches (30 - 70 cm) tall, straight, unbranched, ribbed, and slightly flattened in cross-section; the upper stalk is angled or winged; a reddish-brown sheath, shorter than the leaves, encircles the base of the stalk. A single, cone-like flower spike, ⅜ - ⅝ inch (1 - 1.5 cm) long and bluntly oval, is held at the top of the flower stalk; it is composed of many tan, rounded, overlapping bracts; spikes usually produce only 1 flower per day, which emerges from beneath the rounded tip of a bract. The flower has 3 oblong, yellow petals; sepals do not show above the tip of the bract. Tennessee yellow-eyed grass often occurs with two similar Xyris species. Carolina yellow-eyed grass (X. difformis) has rough leaf surfaces and flat leaf bases. Twisted yellow-eyed grass (X. torta) has swollen leaf bases but its leaves are less than inch (0.5 cm) wide, twisted, with strongly raised veins.

Updates
  • 10/02/2020
  • Reproductive Research

Boyd and Moffett (2003) established test plots to determine the effect of removing a dense shrub layer of St. Johns-wort (Hypericum densiflorum) from a population of Tennessee yellow-eyed grass that occurs on a Georgia Department of Transportation right-of-way. They also studied soil cores to determine the presence of a seed bank. Removal of the shrub layer significantly increased flower production for two consecutive years; however, by the third year, the St. Johns-wort and other shrubby and herbaceous species were again shading the Tennessee yellow-eyed grass and suppressing flowering. Seedling production was increased in the second and third years following shrub removal but there was no significant increase in the total number of plants. They found that pollinator visits to Xyris were significantly more frequent in plots where the shrub layer had been removed. There was no seed bank for this species at the site. Boyd and Moffett also removed shrubs from plots adjacent to the Tennessee yellow-eyed grass stands but concluded that there were no benefits. Boyd et al. (2000) found that Xyris tennesseensis flowers that were cross-pollinated had the greatest seed set but that self-pollinated flowers produced seeds with higher rates of germination.

  • 10/02/2020
  • Propagation Research

Baskin and Baskin (2003) studied seed dormancy and germination requirements of Tennessee yellow-eyed grass. They concluded that: (1) seeds do not require a dormancy-breaking treatment (cold stratification) in order to germinate in late springsummer, implying that under natural conditions seeds would not germinate until warm, summer temperatures were reached; (2) seeds require light to germinate; (3) seeds will germinate under flooded conditions if light is not limited but do not require inundation; and (4) this species forms a small, short-lived (up to 4 years) seed bank which may be stimulated by removing leaf litter and disturbing the soil to a shallow depth. Conditions for growth and establishment of seedlings were less clear, with plants grown in non-native soil failing to thrive. Plants grown in pots of native soil thrived and flowered the summer following germination. The authors recommend that seeds be sown in situ in late spring or summer (when soil moisture levels are high), in full sun, on the surface of undisturbed organic soil from which litter has been removed. Boyd et al. (2000) found that Xyris tennesseensis flowers that were cross-pollinated had the greatest seed set but that self-pollinated flowers produced seeds with higher rates of germination.

Nature Serve Biotics
  • 05/02/2017

Despite extensive surveys, only 16 populations are known to be extant. These extant populations are in highly localized areas of Alabama (4 counties), Georgia (3 counties), and Tennessee (one county). Each site (or occurrence) occupies less than half a hectare. Most of the sites in all 3 states are located on private land and support a few hundred plants. Three (possibly 4) occurrences have been extirpated (2 sites on National Park Service land in Tennessee) in the last few years. At least 4 occurrences are declining due to highway construction and maintenance and one of the largest and newest sites in Alabama is threatened by development (Schotz, pers. comm.).

Linda G. Chafin
  • 01/01/2010

logging use of herbicides in roadside vegetation management road construction gravel quarrying logging and clearcutting soil disturbances exotic pest plants draining and filling habitat for conversion to agriculture or residential development stre

Linda G. Chafin
  • 01/01/2010

Approximately 25 populations are known: 10 in Alabama, 9 in Georgia, 6 in Tennessee.

Linda G. Chafin
  • 01/01/2010

Boyd and Moffett (2003) established test plots to determine the effect of removing a dense shrub layer of St. Johns-wort (Hypericum densiflorum) from a population of Tennessee yellow-eyed grass that occurs on a Georgia Department of Transportation right-of-way. They also studied soil cores to determine the presence of a seed bank. Removal of the shrub layer significantly increased flower production for two consecutive years; however, by the third year, the St. Johns-wort and other shrubby and herbaceous species were again shading the Tennessee yellow-eyed grass and suppressing flowering. Seedling production was increased in the second and third years following shrub removal but there was no significant increase in the total number of plants. They found that pollinator visits to Xyris were significantly more frequent in plots where the shrub layer had been removed. There was no seed bank for this species at the site. Boyd and Moffett also removed shrubs from plots adjacent to the Tennessee yellow-eyed grass stands but concluded that there were no benefits. Baskin and Baskin (2003) studied seed dormancy and germination requirements of Tennessee yellow-eyed grass. They concluded that: (1) seeds do not require a dormancy-breaking treatment (cold stratification) in order to germinate in late springsummer, implying that under natural conditions seeds would not germinate until warm, summer temperatures were reached; (2) seeds require light to germinate; (3) seeds will germinate under flooded conditions if light is not limited but do not require inundation; and (4) this species forms a small, short-lived (up to 4 years) seed bank which may be stimulated by removing leaf litter and disturbing the soil to a shallow depth. Conditions for growth and establishment of seedlings were less clear, with plants grown in non-native soil failing to thrive. Plants grown in pots of native soil thrived and flowered the summer following germination. The authors recommend that seeds be sown in situ in late spring or summer (when soil moisture levels are high), in full sun, on the surface of undisturbed organic soil from which litter has been removed. Boyd et al. (2000) found that Xyris tennesseensis flowers that were cross-pollinated had the greatest seed set but that self-pollinated flowers produced seeds with higher rates of germination.

Linda G. Chafin
  • 01/01/2010

Boyd and Moffett (2003) stress the importance of removing woody competition (in their case, Hypericum densiflorum) from Xyris tennesseensis sites, but point out that shrub removal alone is not sufficient to insure long-term survival of X. tennesseensis and that the presence of a dense shrub layer may offer some benefit to Xyris, which persists in robust vegetative state under the shrubs. After shrub removal, Xyris blooms more vigorously for 2 - 3 years but other herbs also quickly exploit the opened areas and begin to suppress the Xyris. Therefore, for Xyris to persist in an area, there must be suitable nearby microsites into which Xyris can seed and establish plants. A suitable microsite is characterized as a sunny, continually wet, disturbed/exposed patch of mineral soil. Benefits derived from the dense shrub layer include shading and suppression of herbaceous competitors, which allows Xyris to persist until a natural disturbance such as flooding or rock slide opens up appropriate microsites. Management recommendations derived from these observations are: (1) manually cut back Hypericum densiflorum once every three years in mid-March, each time in a different management zone so that a rotation is established for the overall site, (2) manually (no herbicides) remove other woody species annually in September, (3) manually create small, exposed areas of mineral soil next to Xyris plants and spread Xyris seeds in these patches; soil patches should be small (less than a quarter of a square meter) to avoid erosion and not concave to avoid ponding; Xyris spikes can be held over these patches and rolled between the palms of the hands to expel seeds. Other current recommendations include: protect sites from disturbances such as road construction, quarrying, and mechanical clearing; eradicate exotic pest plants; avoid draining or filling wetlands; restore water table to historic levels by reducing groundwater pumping; and use hand-clearing to remove competing shrubs and herbs (Chafin 2007).

Linda G. Chafin
  • 01/01/2010

Rescue threatened populations Identify secure reintroduction sites Conduct range-wide survey for new populations Research effects of loss of genetic diversity and potential levels of inbreeding depression Research seed banking and seedling recruitment Conduct cattle exclosure studies

Linda G. Chafin
  • 01/01/2010

Conserve germplasm. Bring species into national collection. Conduct controlled reintroduction trials.

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Photos
Nomenclature
Taxon Xyris tennesseensis
Authority Kral
Family Xyridaceae
CPC Number 4438
ITIS 196355
USDA XYTE
Common Names Tennessee Yellow-eyed Grass | Tennessee yelloweyed grass
Associated Scientific Names Xyris tennesseensis
Distribution The Ridge and Valley physiographic province of northeast Alabama, the Coastal Plain of northwest Alabama, Ridge and Valley of northwest Georgia, and the Highland Rim of central Tennessee.
State Rank
State State Rank
Alabama S1
Georgia S1
Tennessee S1
Habitat

Sunny, permanent wetlands over calcareous bedrock. Alabama - sand and gravel bars along small to medium sized streams over dolomite and wet seeps. Georgia - spring runs, edges of shallow streams and ponds, seeps, wet meadows, and swales. Tennessee - small calcareous fens on slopes adjacent to headwater streams.

Ecological Relationships

Tennessee yellow-eyed grass reproduces sexually as well as vegetatively by lateral buds that develop in the axils of leaves at the base of the plant. Plants produce one, or rarely two, flowers per day; flowers open in mid-morning and wither soon after noon. Flowers do not produce nectar, but attract pollinators primarily bees and flies, but also weevils and skippers with pollen rewards (Boyd et al. 2003). During the bud stage, flowers are frequently visited by a species of bee (Lasioglossum zephyrum) that has learned to open the buds and remove pollen from the early ripening anthers, thus ensuring that it has first and possibly exclusive access to that flowers pollen (Wall et al 2002).Plants are reported to produce abundant seed (Kral 1990), and Baskin and Baskin (2003) found that seeds will readily germinate if exposed to full light in the warm temperatures of late spring and early summer. Xyris tennesseensis flowers that are cross-pollinated have the greatest seed set but bagged flowers also produced relatively large numbers of seed, indicating that pollinators are not necessary for reproduction. Self-pollinated flowers produce seeds with higher rates of germination (Boyd et al. 2000). Patterns of herbivory, seed predation, and seed dispersal are unknown.

Pollinators
Common Name Name in Text Association Type Source InteractionID

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