Broad-leaved Twayblade (Listera convallarioides)

Life history

Species overview

Broad-leaved Twayblade (Listera convallarioides), a Wisconsin Threatened plant, is found on seepage slopes and ravine bottoms in hardwoods or mixed forests. Blooming occurs early June through late July; fruiting occurs early July through late August. The optimal identification period for this species is late June through late July.

Synonyms: Epipactis convallarioides, Neottia convallarioides, Ophrys convallarioides

Identification

• Distinguishing characteristics: Distinguished from L. auriculata by its flower, which has a narrow-based lip (vs. broad at base with auricles) and pedicels, which are finely glandular pubescent (vs. glabrous). Distinguished from L. cordata by the lip, which is shallowly cleft into 2 rounded lobes (vs. cleft halfway to its base into two sharp-pointed lobes) and leaves, which are longer (over 2.5 cm vs. under 2.5 cm).
• Flower characteristics: Flowers pale green, up to 20; sepals and lateral petals 4 to 5 mm, reflexed; lip greenish, translucent, 9 to 10 mm long and narrowed at the base, usually with a short tooth on each side near the narrow base.
• Fruit characteristics: Capsule tapering on both ends, 8 cm long, glabrous.
• Leaf characteristics: Opposite, arranged in a single pair, each leaf roadly ovate, 3 to 7 cm long and longer than the peduncle.

Phenology

• Blooming phenology: early June through late July
• Fruiting phenology: early July through late August
• Optimum time to identify: The optimal identification period for this species is late June through late July

Other

• Growth form: Forb-erect
• Vegetative reproduction:
• Life cycle: Perennial
• Comments: Associated Species: Acer saccharum, Tsuga canadensis, Betula alleghaniensis, Thuja occidentalis, Carex scabrata, Circaea alpina, Aster macrophyllus.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - state and federal - and the rank (S and G Ranks) for Broad-leaved Twayblade (Listera convallarioides). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.

Habitats and landscapes

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

General habitat information

• Habitat description: Found on seepage slopes and ravine bottoms in hardwoods or mixed forests.
• Soils: Wet soils.

Natural communities

This table lists the natural communities that are associated with Broad-leaved Twayblade. Scores for natural community associations are: "significant" association (score=3), "moderate association" (score=2) or the species can be present but is only weakly associated with the community (score=1).

Ecological landscapes

This table lists the ecological landscape association scores for Broad-leaved Twayblade. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Species guidance

The Endangered Resources Program has developed avoidance measures and management guidelines for plants on the Natural Heritage Working List. These are a work in progress, and we welcome your suggestions and feedback. Sources used in developing this information can be found here.

Avoidance measures

These are specific actions designed to avoid "take" (mortality) of this species.

• Avoid known individual plant locations and conduct operations elsewhere when they are least likely to cause damage. Ideally, this would involve frozen, snow-covered ground. However, in areas of the state where frozen conditions are unreliable, very dry soils late in the growing season might be the best available alternative. Consult with a biologist, if needed.
• Avoid broadcast spraying of herbicides; use care with spot spraying.
• Avoid locating landings, staging areas, or access routes on or near known populations.
• Avoid site preparation that heavily disturbs herbaceous ground layer and soil; these include bulldozing and furrowing, as well as grubbing and stump removal.

Management guidance

Management guidelines are additional considerations that may help maintain or enhance habitat for this species

• Maintain high forest canopy cover; this species requires shaded habitat conditions.
• Follow BMPs, especially around streams and use care near ravines, steep slopes, cliffs, rock outcrops, etc.
• Buffer management around unique microhabitats such as ephemeral ponds, seeps, etc.
• Minimize disturbance to hydrology, including soil disturbance from rutting.
• Survey for and control invasive plants prior to conducting timber operations, as these can be spread by vehicles and often respond vigorously to increased light; see forestry BMPs for invasive species.

Other resources

Links to additional Broad-leaved Twayblade information

Other links related to vascular plants (all exit the DNR website)

• Wisconsin Flora
• NatureServe Explorer
• Atlas of Wisconsin Prairie and Savanna Flora - Wisconsin State Herbarium
• USDA - NRCS Plants Database
• USGS Midwestern Wetland Flora - field office guide to plant species
• eFloras
• Cofrin Center for Biodiversity Herbarium
• Intermountain Herbarium Grasses of North America
• Orchids of Wisconsin

Photos

Click to view a larger version. Please considering donating a photo to the Natural Heritage Conservation Program for educational uses. Photo use