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Small Whorled Pogonia (Isotria medeoloides) [threatened]

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Additional Information

Small whorled pogonia

IN BRIEF

Habitat:
Upland forests

Main Threats:
Habitat destruction
Recreational activities
Collection

Fun Fact:
Small whorled pogonia is a type of orchid.


Map of small whorled pogonia distribution in US
Distribution of small whorled pogonia in the US.
(Click image for full-size)

Map of small whorled pogonia distribution in New Jersey by municipality
Map of small whorled pogonia distribution in New Jersey by municipality

Overview

Small whorled pogonia was federally listed as an endangered species in 1982, and reclassified as a threatened species in 1993.

A perennial member of the orchid family, small whorled pogonia produces a smooth, hollow stem from 2 to 14 inches tall and topped by five or six leaves in a circular arrangement (false whorl). One or two flowers stand in the center of the whorl of leaves. The leaves are milky-green or grayish-green, and the flower is yellowish-green with a greenish-white lip. In the northern part of the species’ range, plants with flowering buds emerge from the leaf litter in May and bloom in June.

Small whorled pogonia grows in a variety of upland, mid-successional, wooded habitats, usually mixed-deciduous or mixed-deciduous/coniferous forests that are in second or third-growth successional stages. Canopy trees are typically 40 to 75 years old and 8 to 18 inches in diameter. Characteristics of this species’ habitat include a sparse herb and shrub layer, a relatively open understory canopy, thick leaf litter on the forest floor, and gently sloping ground. Soils in which small whorled pogonia grows are generally acidic and dry during most of the growing season. Many sites where this plant occurs are underlain by soils with a hardpan layer that impedes the downward flow of water and leads to the formation of shallow braided channels on the ground surface. Small whorled pogonia is almost always found in proximity to features that create long-persisting breaks in the forest canopy; light availability could be a limiting factor for this species.

Typical canopy species associated with small whorled pogonia include red maple (Acer rubrum), eastern hemlock (Tsuga canadensis), northern red oak (Quercus rubra), white oak (Q. alba), black oak (Q. velutina), scarlet oak (Q. coccinea), white pine (Pinus strobus), American beech (Fagus grandifolia), sweet-gum (Liquidambar styraciflua), and tulip poplar (Liriodendron tulipifera). Typical ground layer species associated with small whorled pogonia include partridge berry (Mitchella repens), Indian cucumber root (Medeola virginiana), New York fern (Thelypteris noveboracensis), sweet lowbush blueberry (Vaccinium pallidum), rattlesnake plantain (Goodyera pubescens), red maple seedlings, oak seedlings, Canada mayflower (Maianthemum canadense), wintergreen (Gaultheria procumbens), starflower (Trientalis borealis), running cedar (Lycopodium digitatum), Virginia creeper (Parthenocissus quinquefolia), cat-brier (Smilax glauca), and Christmas fern (Polystichum acrostichoides).

Habitat destruction is the primary threat to the small whorled pogonia. Residential or commercial development, both directly and indirectly, is a primary factor in the destruction of habitat for this species. Other threats include recreational use of the habitat, herbivory, collection, and inadvertent damage from research activities.

Distribution

Species Range: Although sparse, small whorled pogonia is widely distributed, with a primary range extending from southern Maine and New Hampshire through the Atlantic Seaboard states to northern Georgia and southeastern Tennessee. Outlying colonies have been found in the western half of Pennsylvania, Ohio, Michigan, Illinois, and Ontario, Canada.

Distribution in New Jersey: Small whorled pogonia is currently known to occur in Sussex and Passaic Counties. The species formerly occurred in Bergen and Hunterdon Counties.


Last updated: January 28, 2014
New Jersey Field Office
Northeast Region Ecological Services
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