Platanthera integrilabia

Treated at the species level as Platanthera integrilabia by Kartesz (1994, 1999). Formerly treated as Habenaria blephariglottis var. integrilabia; if treated as a species in Habenaria, this taxon has the name H. correllii Cronquist.

Platanthera integrilabia is a perennial herb endemic to seven states in the southeastern United States. It is currently known from 52 populations, primarily on the Cumberland Plateau of Tennessee and Kentucky. Many occurrences consist of fewer than 100 plants, but some have upwards of 1000 plants. The species is rare throughout its range and is extirpated/historical in North Carolina and potentially South Carolina. Many surviving populations are not vigorous and exhibit very poor seed set. The habitat where this species grows has often been drained or turned into farm ponds or hog lots or has experienced residential and commercial construction. Deer browse is a significant problem that decreases seed set. Active management may be required to inhibit woody succession and prevent canopy closure at sites where the species is found but timber harvest must be carried out carefully to protect the plants and their wetland habitat from damage. Development, canopy closure, improper timber harvest techniques, rights-of-way maintenance activities, poaching, and invasive nonnative plants remain threats. Despite protection of several occurrences on federal lands, declines have been observed due to silviculture activities and mismanagement of adjacent properties. Monitoring of populations, including in states where the species has historically occurred, should be conducted to improve our understanding of reproduction, plant abundance, threats, and trends, as well as continuing conservation measures to protect the species.

Platanthera integrilabia occurs in the southeastern United States in six ecoregions across seven states: the Appalachian Plateaus of Kentucky, Tennessee, and Alabama; the Central Appalachians of Kentucky; the Coastal Plain of Alabama and Mississippi; the Blue Ridge Province of Georgia, North Carolina (historic), and Tennessee; the Ridge and Valley Province in Alabama; and the Piedmont of Georgia and South Carolina (FNA 2002a, USFWS 2012, USFWS 2022). The recent finding of this species in the Cumberland Mountains in Kentucky may lead to additional population discoveries and known range expansion (Littlefield, pers. comm., 2024).

By applying a 1 km separation distance to NatureServe Network occurrence data documented between the years of 1995 and 2023, it is estimated that there are 77 occurrences which may be considered 52 populations due to their close proximity, pending further field research and excluding seven sites that were failed to find, one site considered historic, and four sites considered extirpated (NatureServe 2023, USFWS 2022). Most occurrences are located in Kentucky and Tennessee. One occurrence in Tennessee was transplanted to an introduced site within the historic range of the species (USFWS 2022, Wooten et al. 2020). New occurrences continue to be found in Alabama, Kentucky, and Tennessee (Crabtree, Littlefield, and Schotz, pers. comm., 2024). However, occurrences in South Carolina have not been seen in more than twenty years despite repeated surveys (Bradley and Tessel, pers. comm., 2024).

Threats to Platanthera integrilabia include habitat degradation (alteration, fragmentation, succession, forest management practices, feral hogs, right-of-way maintenance, invasive species, recreation), plant damage (deer browse, poaching), and a low reproductive capacity (Southern Appalachian Species Viability Project 2002, USFWS 2021).

Habitat modification is the greatest threat to Platanthera integrilabia especially actions like logging operations, development (commercial, residential), road projects, pond construction (related to agriculture), and beaver activities which can alter sites to become unnaturally wet by damming drainage. These activities disrupt and alter hydrological regimes, which have the most severe and long-term impacts on P. integrilabia populations (Shea 1992). Although P. integrilabia may show an increase in reproduction and growth immediately after logging activities, which can continue for several years, the long-term effects have not been well studied (Shea 1992, Williams 2000). Logging activities lead to erosion, runoff, and alteration of hydrology for the surrounding landscape, especially sensitive habitats where P. integrilabia grows. Additionally, shrubby secondary growth often follows logging, which may result in a decline due to shading and competition. The opening of the forest canopy may also provide habitat for aggressive non-native plant species, and the following non-native invasive species have been documented as problematic: Lespedeza bicolor, Ligusteum sinense, Microstegium vimineum, and Perilla frutescens. Habitat changes from non-native invasives may be more severe than outcompetition, and it has been documented that Microstegium vimineum increases soil pH (McGrath and Binkley 2009), which may reduce habitat quality for P. integrilabia. In 2000, M. Williams noted native species such as sedges, grasses, and other herbaceous species can out compete P. integrilabia in sites lacking an overstory. Other activities that disrupt surface water flow include ATVs, off-highway vehicles, and horseback riding.

Damage to plants occurs through illegal harvest, herbivory by deer, feral hogs that uproot plants, aphids, disease, and use of herbicides. In 1991, at least two nurseries in TN were reported to have collected Platanthera integrilabia plants for sale. It has been suggested the type locality in KY was extirpated by plant collectors (Ettman and McAdoo 1979). Observations of herbivory by deer are common: deer favor the flowering stalks which decreases seed set. In addition, many orchids cannot replace loss of tissue until the next growing season. The loss of tissue from foraging animals could result in death for the plant (Sheviak 1990). In addition to lowering fruit set, herbivory can have a long-term negative impacts upon the site viability for the species (Zettler and Fairley 1990). Recently, as much of 20% of some populations in Kentucky have been noted to abort flowering in conjunction with aphids observed in stems (Littlefield, pers. comm., 2024). Many sites occur in right-of-ways and these sites are subjected to herbicides to control vegetative growth. The manual or mechanical clearing of vegetation from the right-of-ways seems to benefit the species (Shea 1992), though care needs to be taken to avoid impacts from machinery and timing of treatments.

Platanthera integrilabia is susceptible to fungal infections (Zettler and Fairley 1990).

Threats are compounded by low reproductive capacity and isolated populations. It is unclear how much low seed set may be related to herbivory and lack of successful pollinators (Zettler and Fairley 1990, Shea 1992, Williams 2000, Bailey 2001).

This species has been ranked as "highly vulnerable" to climate change (Glick et al. 2015), predicting a decrease in species's abundance and range extent by 2050. Drought events may increase mortality, reduce seed set, and reduce germination and recruitment (USFWS 2021). Increased storm intensity could erode habitat and increase sedimentation (USFWS 2021).