Pycnanthemum torrei - Benth.
Torrey's Mountainmint
Other Common Names: Torrey's mountainmint
Taxonomic Status: Accepted
Related ITIS Name(s): Pycnanthemum torrei Benth. (TSN 32656)
Unique Identifier: ELEMENT_GLOBAL.2.141413
Element Code: PDLAM1N0G0
Informal Taxonomy: Plants, Vascular - Flowering Plants - Mint Family
Image 21746

© North Carolina Natural Heritage Program

 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Lamiales Lamiaceae Pycnanthemum
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Concept Reference
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Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Pycnanthemum torrei
Taxonomic Comments: As generally treated now, excludes "var. leptolon", now considered to be included in Pycnanthemum verticillatum (Kartesz, 1994).
Conservation Status
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NatureServe Status

Global Status: G2
Global Status Last Reviewed: 10Mar2017
Global Status Last Changed: 16Nov1992
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: G2 - Imperiled
Reasons: There are approximately 35 confirmed extant occurrences (although more populations probably still survive in unsearched parts of its wide range). The species is apparently declining throughout its range and is historic in Illinois, Missouri, and New Hampshire. Surviving populations are widely scattered and many are threatened by woody succession, development, and recreational use of its habitat.
Nation: United States
National Status: N2

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Connecticut (S1), Delaware (S1), District of Columbia (SX), Illinois (SH), Kansas (SNR), Kentucky (SNR), Maryland (S1), Missouri (SH), New Hampshire (S1), New Jersey (S1), New York (S1), North Carolina (S1), Pennsylvania (S1), South Carolina (SNR), Tennessee (S1), Virginia (S2), West Virginia (S1)

Other Statuses

NatureServe Global Conservation Status Factors

Range Extent Comments: Pycnanthemum torrei occurs in the south-central and eastern United States. Once ranged from southern New Hampshire to Georgia, west to Illinois. Historic in Illinois, Missouri, and New Hampshire. The plant is of unknown status in Georgia (Allison 1994). A Pycnanthemum taxon collected from Indiana was determined not to be P. torrei but perhaps a hybrid or other unknown variant (Homoya 1994).

Area of Occupancy: 26-125 4-km2 grid cells
Area of Occupancy Comments:  

Number of Occurrences: 21 - 80
Number of Occurrences Comments: There are about 35 extant occurrences: Connecticut (3 extant occurrences, 1 historic), Delaware (two extant occurrence, 2 historic), Illinois (one historic occurrence), Maryland (4 extant occurrences, 4 possibly or most likely extirpated, 2 historic, 2 possible erroneous records), New Hampshire (one historic), New Jersey (3 extant occurrences, 10 historic), New York (3 extant occurrences, 9 historic), North Carolina (5 extant occurrences, 11 historic), Pennsylvania (3 extant occurrences, 13 historic or extirpated occurrences), Virginia (10 extant occurrences, 5 historic), West Virginia (1 extant occurrence) (Herkert 1991, McAvoy 1992b, NatureServe Central Database 2015, NLI 1981, DE NHP 1993, Rhoades and Klein 1993, Weakley 1994).

Population Size Comments: Total abundance unknown; apparently highly local and in moderate numbers. Populations occur as small, dense colonies. Species is often difficult to identify.

Number of Occurrences with Good Viability/Integrity: Few (4-12)

Overall Threat Impact: Medium
Overall Threat Impact Comments: Primary threats include succession and invasion of habitat by exotic, weedy plants, such as Japanese honeysuckle (Lonicera japonica). Spraying of herbicides by railroad, highway, or utility crews for right-of-way maintenance threatens populations near these corridors. Other threats to populations include habitat destruction due to general development, road construction, timber harvest, soil disturbance, refuse dumping, trampling by humans, horses, and tractors, and recreational pressures.

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: This species is apparently declining throughout its range. Historic occurrences out-number extant occurrences in almost all of the states having available information within the range of the species. The species is now considered historical in New Hampshire, North Carolina, and Missouri.

Long-term Trend: Decline of 50-70%
Long-term Trend Comments: Many historic and some extirpated locations for this plant.

Other NatureServe Conservation Status Information

Distribution
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Global Range: Pycnanthemum torrei occurs in the south-central and eastern United States. Once ranged from southern New Hampshire to Georgia, west to Illinois. Historic in Illinois, Missouri, and New Hampshire. The plant is of unknown status in Georgia (Allison 1994). A Pycnanthemum taxon collected from Indiana was determined not to be P. torrei but perhaps a hybrid or other unknown variant (Homoya 1994).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States CT, DCextirpated, DE, IL, KS, KY, MD, MO, NC, NH, NJ, NY, PA, SC, TN, VA, WV

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
CT New Haven (09009)
DE Kent (10001), Sussex (10005)
IL Pope (17151)*
MD Anne Arundel (24003)*, Baltimore County (24005), Caroline (24011)*, Cecil (24015), Dorchester (24019)*, Frederick (24021), Howard (24027)*, Montgomery (24031)*, Prince Georges (24033)*
MO Butler (29023)*, Dunklin (29069)*, New Madrid (29143)*, Pemiscot (29155)*, Stoddard (29207)*
NC Alexander (37003)*, Caswell (37033), Cleveland (37045)*, Gaston (37071)*, Granville (37077)*, Haywood (37087)*, Jackson (37099)*, Macon (37113)*, Orange (37135), Person (37145)*, Wilkes (37193)*
NH Hillsborough (33011), Rockingham (33015)
NJ Bergen (34003), Essex (34013), Gloucester (34015)*, Hudson (34017)*, Hunterdon (34019)*, Middlesex (34023)*, Monmouth (34025)*, Morris (34027)*, Passaic (34031), Union (34039)*, Warren (34041)*
NY Bronx (36005)*, Dutchess (36027), New York (36061)*, Richmond (36085), Rockland (36087), Westchester (36119)*
PA Bedford (42009), Berks (42011)*, Bucks (42017)*, Delaware (42045)*, Franklin (42055)*, Indiana (42063)*, Lancaster (42071)*, Northampton (42095)*
TN Anderson (47001), Blount (47009)*, Putnam (47141)*
VA Arlington (51013)*, Augusta (51015), Bland (51021), Campbell (51031)*, Dinwiddie (51053), Fairfax (51059), Fauquier (51061), Franklin (51067), Giles (51071), Greensville (51081), Halifax (51083), Lunenburg (51111), Nelson (51125), Prince William (51153), Southampton (51175)*, Sussex (51183)*
WV Fayette (54019), Jefferson (54037)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
01 Merrimack (01070006)+, Quinnipiac (01100004)+, Housatonic (01100005)+
02 Lower Hudson (02030101)+, Bronx (02030102)+*, Hackensack-Passaic (02030103)+, Sandy Hook-Staten Island (02030104)+, Raritan (02030105)+*, Middle Delaware-Musconetcong (02040105)+*, Lehigh (02040106)+*, Crosswicks-Neshaminy (02040201)+*, Lower Delaware (02040202)+*, Schuylkill (02040203)+*, Broadkill-Smyrna (02040207)+, Raystown (02050303)+, Lower Susquehanna-Swatara (02050305)+*, Lower Susquehanna (02050306)+, Gunpowder-Patapsco (02060003)+, Choptank (02060005)+*, Patuxent (02060006)+*, Conococheague-Opequon (02070004)+*, South Fork Shenandoah (02070005)+, Shenandoah (02070007)+, Middle Potomac-Catoctin (02070008)+*, Monocacy (02070009)+, Middle Potomac-Anacostia-Occoquan (02070010)+, Rapidan-Upper Rappahannock (02080103)+, Western Lower Delmarva (02080109)+, Eastern Lower Delmarva (02080110)+*, Middle James-Buffalo (02080203)+
03 Upper Roanoke (03010101)+, Middle Roanoke (03010102)+, Lower Dan (03010104)+, Nottoway (03010201)+, Meheriin (03010204)+, Upper Tar (03020101)+*, Haw (03030002)+, South Yadkin (03040102)+*, Upper Catawba (03050101)+*, Upper Broad (03050105)+*, Tugaloo (03060102)+*
05 Conemaugh (05010007)+*, Middle New (05050002)+, Lower New (05050004)+, Upper Cumberland-Cordell Hull (05130106)+*, Caney (05130108)+*, Lower Ohio-Bay (05140203)+*
06 Pigeon (06010106)+*, Watts Bar Lake (06010201)+*, Upper Little Tennessee (06010202)+*, Lower Clinch (06010207)+
08 Lower St. Francis (08020203)+*, Little River Ditches (08020204)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A perennial herb, up to 1.5 m tall with square stems and narrow, opposite leaves. Herbage has a mint-like odor. Small white to purple flowers are in compact clusters. Fruit is a nutlet. Blooms from late June to September.
General Description: Pycnanthemum torrei is an herbaceous perennial with elongated rhizomes and erect, quadrangular freely branched stems to 3 ft. high. The leaves are about .5 in. wide and are usually three times as long as wide. The white to purple flowers are 2-lipped (upper entire or notched, lower 3-lobed), and found in compact flat-topped clusters at the tip of the stems and upper branches. (Gleason 1963, Rickett 1963, Steyermark 1963, Radford et al. 1964, Fernald 1970, Gleason and Cronquist 1991, Herkert 1991, Rhoades and Klein 1993).
Technical Description: Perennial herbs, commonly 70-80 cm tall, but up to 1 m. Stems branching in the upper parts, with short lateral branches, the median internodes about equal to the subtending leaves, or longer, rarely shorter, rather thinly pubescent, the hairs uneven, spreading, or curling upward, and uniformly distributed. Leaves narrowly lanceolate, narrowing toward the base, mostly at least 3 times as long (4.5-9 cm) as wide (0.5-1 cm) and not more than 1.5 cm wide, entire or the larger serrate, essentially glabrous, scabrous along the edges, the midvein sometimes hairy, bearing commonly 3-5 pairs of veins, the uppermost pair extending to the tip, median petioles 1-4 mm long. Inflorescence densely capitate, only the lower (or no) branchlets within the flower-clusters evident in fruit. Flowers small, in crowded or head-like cymes terminating the stem and branches, or also sessile in the axils of the upper leaves, subtended by a pair of leaflike bracts, the inner bracts leaflike, with a prominent midrib, their edges pilose. Corolla gradually enlarged upward, 3.5-5 mm long, purple to white, more or less distinctly bilabiate, the upper lip entire or merely emarginate, 2.5-3.5 mm tall, the lower lip 3-lobed, often purple- spotted. Calyx 4-5 mm long, 10-13 nerved, often 2-lipped, with the posterior three slightly fused at the base, the anterior pair 1-2 mm long, pubescent on the edges with rather stiff hairs, the lobes shorter than the tube. Calyx teeth 1-1.5 mm long, sharp. Stamens 4, commonly exsert, straight and divergent, the pollen-sacs parallel. Involucral bracts lanceolate, acuminate to aristate, leaf-like and not cuspidate, essentially glabrous. Nutlets glabrous or sometimes hairy at the tip. Chromosome number: 2n=78-80. (Grant and Epling 1943, Gleason and Cronquist 1991).
Diagnostic Characteristics: Pycnanthemum torrei is in the group of Pycnanthemum that have long narrow leaves, mostly more than three times as long as wide and not more than 15 mm wide (Gleason and Cronquist 1991; Weakley 2004). Within the group of narrow-leaved Pycnanthemum, there are several similar Pycnanthemum species: P. clinopodioides, P. flexuosum, P. tenuifolium, P. verticillatum, and P. virginianum. Characters that distinguish Pycnanthemum torrei include the calyx lobes and pubescence. For a technical description see Gleason and Cronquist (1991).

P. torrei is distinguished from P. clinopodioides by the calyx lobes. P. torrei has calyx lobes that are equal or nearly equal in length and that are not tipped with long jointed bristles (Rhoads and Block 2000; Weakley 2004). The calyx lobes of P. clinopodioides are not of equal length and are tipped with a few long (1-3 mm) jointed bristles (Rhoads and Block 2000; Weakley 2004).

P. torrei differs from P. flexuosum in having shorter calyx lobes; P. torrei has calyx lobes that are 1-1.5 mm long whereas P. flexuosum has calyx lobes that are 1.5-5 mm long (Gleason and Cronquist 1991; Weakley 2004).

Compared to P. tenuifolium, P. torrei has leaves with at least some pubescence on the lower surface; P. tenuifolium has glabrous leaves (Gleason and Cronquist 1991; Weakley 2004).

The most reliable characters that distinguish Pycnanthemum torrei from P. verticillatum and P. virginianum are the shape and size of the calyx lobes (Snyder 1994; Gleason and Cronquist). In P. torrei, the lobes are lanceolate, usually come to a slender point, and are 1-1.5 mm long or longer. In P. verticillatum, the calyces are narrowly deltoid, without sharp tips, and 0.7-1 mm long. P. virginianum also has shorter calyx lobes without sharp tips (Gleason and Cronquist 1991; Rhoads and Block 2000). In addition, Pycnanthemum torrei differs from these two species in having softer and less veiny leaves (Gleason and Cronquist 1991).

Duration: PERENNIAL
Ecology Comments: Pycnanthemum torrei flowers from late June to October (Rickett 1963, Steyermark 1963, Fernald 1970, Gleason and Cronquist 1991, NJ NHP 1994c).

In Virginia this species is located on a broad "dome" of basic rock (gabbro?), which is several miles across and more resistant to erosion than the surrounding area (VA DNH 1992b). Populations in Maryland have been found in semi-basic soil from igneous rock, on serpentine, and other neutral alfisols (MD NHP 1994b).

Populations occur as small, dense colonies which are vulnerable to destruction from minor habitat perturbations or stochastic events (MD NHP 1994a).

Terrestrial Habitat(s): Forest - Hardwood, Forest/Woodland, Woodland - Hardwood
Habitat Comments: Dry upland forests, dry rocky woodlands over mafic, ultramafic, or calcareous rocks, edges of sandstone glades, dry-mesic barrens, thickets, upland meadows, and powerline rights-of-way (Gleason 1963, Rickett 1963, Fernald 1970, NLI 1981, Gleason and Cronquist 1991, Herkert 1991, University of Minnesota Herbarium [MIN], Rhoads and Klein 1993; Rhoads and Block 2000; Weakley 2004).

The habitat of this species as found in particular states is as follows:

Connecticut: Dry, rocky woods and thickets in the Central Lowlands region. Associated plant species include Andropogon sp., Carya ovalis, Fraxinus americana, Juniperus communis, J. virginiana, and Viburnum rafinesquianum. Occurrences have been found at elevations ranging from 500-600 feet. (CT NDD 1994a, CT NDD 1994b, CT NDD 1994c, CT NDD 1994d).

Illinois: Upland dry-mesic barrens (IL NHD 1994; Herkert 1991).

Delaware: Dry to mesic oak woods in partial shade, along the edge of an old logging road. Associated plant species include Desmodium paniculatum, Lycopodium complanatum, Sabatia angularis, and Solidago rugosa. Habitat has been described from historic records as wooded banks, rocky woods, and the edge of woods. (McAvoy 1992a, McAvoy 1992b).

Maryland: Open, southern exposures of xeric, rocky, wooded habitat. It has also been found along dry powerline corridors with associated plant species such as Parthenocissus sp., Pycnanthemum flexuosum, Pycnanthemum incanum and Rhus sp. In addition, this plant has been found in a man-made, roadside oak opening in filtered light, and scattered along a sphagnum bank, dampened by water seeping from uplands. Another occurrence was found in a little bluestem (Schizachyrium scoparium) grassland with associates such as Andropogon gerardii, Heliopsis helianthoides, Lonicera japonica, Pycnanthemum flexuosum, Pycnanthemum incanum, Solidago patula, and Sorghastrum nutans. Occurrences have been located at elevations ranging from 110-1320 feet. (MD NHP 1994b).

Missouri: The habitat of a historic site is along a stream at an elevation of 830 feet (MO NHD 1994).

New Hampshire: This species has been found on a rich wooded slope at an elevation of 475 feet (NH NHI 1992).

New Jersey: Open, dry, rocky glades in oak/hickory forests, on slopes near the tops of south- facing hillsides. Most occurrences are from trap rock or diabase rock formations. Habitat is within the traprock glade/rock outcrop community. (NJ NHP 1994c, Snyder 1994).

New York: Open woodlands and cedar glades on limestone, with associates such as Aster laevis, Bouteloua curtipendula, Onosmodium virginianum, Pycnanthemum incanum, and Sorghastrum nutans (Zaremba 1992a, Zaremba 1992c, NY NHP 1994b).

North Carolina: In the mountains and in the Piedmont, in rich woods, and usually on rock such as gabbro or diabase. Some sites seem to have been maintained in the past as opened areas, probably by fire and other activities. (University of Minnesota Herbarium [MIN], Weakley 1994).

Pennsylvania: Dry upland woods, streambanks, and open thickets. The plant has been located at elevations ranging from 820-1060 feet (PNDI-E 1994).

Virginia: Dry, rocky, deciduous woods, along roadsides, and in thickets near streams. One occurrence has been found on the western slope of an exposed ledge with the following associate plant species: Cheilanthes lanosa, Danthonia spicata, Triosteum angustifolium, and other herbaceous xerophytes. At another occurrence in an open right-of-way through an extensive oak-hickory forest, plants were found on the southwest slope of a small diabase knob in dry, rocky silt loam with plant associates such as Helianthus divaricatus, Phaseolus polystachios, P. tenuifolium, and woody invading species such as Cercis canadensis and Rubus spp. Occurrences within this state have been found at elevations ranging from 35-1400 feet. (VA DNH 1992b).

West Virginia: Dry openings of woods and flatrock exposures (hard sandstone) along streams. One occurrence was located at an elevation of 940 feet. (WV NHP 1992a, WV NHP 1992b).

Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: Preserve designs should include adequate buffer area surrounding occurrences to allow for management activities and prescribed fire requirements, including the effects of smoke drift. At sites where grasslands or other open habitats exist or have in the past, mowing or burning may be required to keep natural plant succession controlled. Weedy plant species, such as Japanese honeysuckle (Lonicera japonica), should be eliminated from habitats using control methods. Occurrences need to be protected from threats such as development of habitat, timber harvest, trampling by humans and animals, herbicide application, and recreation pressures. Populations should be visited on a frequent basis to assess population size and vigor, reproductive success, habitat quality, and threats. Research is needed to clarify outstanding taxonomic uncertainties, and to determine better ways of identifying differences between closely-related taxa.
Restoration Potential: For populations experiencing encroachment by woody plant species or overcrowding by exotic or invasive plants, removal by cutting or mowing of these species or the use of prescribed fire will restore habitat quality.
Preserve Selection & Design Considerations: Preserve designs should include enough buffer area surrounding occurrences to allow for management activities. At sites where it is deemed necessary to maintain open habitat through the use of prescribed fire, preserves should take this into account, as well as the effects of smoke drift toward neighboring areas.
Management Requirements: In states where populations are small, at least two occurrences should be protected. Where right-of-ways (railroad, highway, utility, etc.) exist, maintenance crews should use cutting methods instead of spraying herbicides. (WV NHP 1992b).

In grassland habitat such as that found at a Maryland occurrence, a continual mowing regime is needed in order to keep natural plant succession in check (MD NHP 1994b).

The use of fire as a management tool may be required for sites which have been maintained in the past as opened areas (either by fire or other means) (Weakley 1994).

Control of exotic and weedy plant species (such as Lonicera japonica) is needed to eliminate the threat of crowding out Pycnanthemum torrei within its habitat (MD NHP 1994b).

Monitoring Requirements: Monitor extant sites on an annual basis, making assessments of threats, habitat quality, and population size and vigor. Occurrences which have not been visited recently should be revisited and have their status updated.

Management Programs: There is no management program known to be in effect for this species.
Monitoring Programs: Monitoring for presence or absence of Pycnanthemum torrei is conducted for occurrences in New York and Delaware (Zaremba 1992a, McAvoy 1992b).
Management Research Programs: No research programs for management purposes are known to be in effect for this species.
Management Research Needs: Additional field surveys need to be conducted in order to update the current status of this species across its range. These surveys would allow for the discovery of new populations and the rediscovery of historic populations (McAvoy 1992b, PNDI-E 1992, WV NHP 1992b, MD NHP 1994a).

Beneficial management practices need to be determined for better management of populations (MD NHP 1994a). In addition, knowledge of habitat requirements would also make for better management (McAvoy 1992b).

Additional topics: Pycnanthemum torrei has been considered synonymous with the following plant names by various botanists over the years: Brachystemon verticillatum Michx., Koellia clinopodioides (T. & G.) Kuntze, K. leptodon (Gray) Small, K. torrei Kuntze, K. verticillata (Michx.) Kuntze., K. virginiana, P. clinopodioides T. & G., P. leptodon, P. torrei var. leptodon (Gray) Boomhour, P. verticillatum (Michaux) Persoon. (Grant and Epling 1943, Gleason 1963, Radford et al. 1964, Britton and Brown 1970, Fernald 1970, Gleason and Cronquist 1991).

Common names for Pycnanthemum torrei include Torrey's mountain mint, mountain mint. The species name is named after John Torrey, 1796-1873. The genus name is derived from the Greek word pycnos, meaning dense, and anthemon, meaning flower, referring to the compact inflorescence. (Fernald 1970, Gleason and Cronquist 1991, Herkert 1991).

Range distribution maps for Pycnanthemum torrei may be found in the following sources: Grant and Epling (1943), Steyermark (1963), NLI (1981), Herkert (1991), DE NHP (1992), Zaremba (1992b), Rhoades and Klein (1993), CT NDD (1994c), NY NHP (1994a).

Illustrations of this species may be found in the following sources: Chambers (1961)(chromosomes), Gleason (1963), Britton and Brown (1970).

In a study of the chromosome numbers and breeding systems in Pycnanthemum, Chambers (1961) examined preserved flowering material of P. torrei which showed that the anthers were normal and well developed and that an abundance of good pollen was produced. A chromosome count of 2n=ca. 78-80 was obtained from root-tip cells.

In another study of Pycnanthemum, by Grant and Epling (1943), a useful diagram (Figure 1) showed the possible interrelationships of species of the genus broken down into the two main groups (or phylads), in one of which P. torrei has been placed.
Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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Excellent Viability: An A-ranked occurrence of Pycnanthemum torrei should have more than 500 plants in contiguous habitat and having adequate recruitment to sustain population numbers at current levels. The population should occur in large areas of undisturbed dry upland forests and meadows, dry-mesic barrens, rocky woods, and sandstone glades surrounded by a significant buffer area and free of threats.
Good Viability: A B-ranked occurrence of Pycnanthemum torrei should have between 100 and 500 plants in contiguous dry upland forests and meadows, dry-mesic barrens, rocky woods, and sandstone glades surrounded by a buffer area and significant patches of unoccupied, suitable habitat present for future colonization. Habitats may have minor threats, none of which are directly impacting or significantly degrading the habitat (i.e. site may have trails or be bisected by a road, or be located adjacent to inactive quarries, agricultural or cleared land, or low density deveolopment).
Fair Viability: A C-ranked population of Pycnanthemum torrei should have between 50 and 100 plants occurring in small areas of dry upland forests and meadows, dry-mesic barrens, rocky woods, and sandstone glades; OR any moderate to large-sized habitat that is significantly disturbed and fragmented; buffer less than optimal but some remaining suitable habitat for future expansion.

Poor Viability: A D-ranked population of Pycnanthemum torrei should have fewer than 50 plants or a population of any size exhibiting a continual decline over a period of several years. The population should occur in small areas of dry upland forests and meadows, dry-mesic barrens, rocky woods, and sandstone glades with no buffer area nor additional suitable habitat for future expansion; OR, habitat heavily, and possibly irreversibly, disturbed or altered, or with significant, ongoing, un-natural disturbance directly impacting the population.

Justification: The rank specifications for Pycnanthemum torrei are based on current populations and expert opinion.
Key for Ranking Species Element Occurrences Using the Generic Approach (2008).
Date: 29Nov2004
Author: Amoroso
Notes: BCD rank specifications by Ambrose, D. (1996); Neid (1998)
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 12Nov2015
NatureServe Conservation Status Factors Author: Ambrose, D. (1996); Neid (1998)., rev. A. Tomaino (2004), rev. A. Treher (2015)
Management Information Edition Date: 27Dec1994
Management Information Edition Author: Ambrose, Donn M., rev. A. Tomaino (2004)
Management Information Acknowledgments: We are indebted to all the botanists, ecologists, information managers, and others who took the time to provide the information necessary for the preparation of this and many other Element Stewardship Abstracts.
Element Ecology & Life History Edition Date: 27Dec1994
Element Ecology & Life History Author(s): DONN M. AMBROSE, rev. A. Tomaino (2004)

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
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  • Bentham, G. 1836-1832 Oct. (in fours). Habiatarum genera et species: or, a description of the genera and species of plants of the order Labiatae; with their general history, characters, affinities, and geographical distribution. London (James Ridgeway and Sons).

  • Bentham, G. 1836-1832 Oct. (in fours). Habiatarum genera et species: or, a description of the genera and species of plants of the order Labiatae; with their general history, characters, affinities, and geographical distribution. London (James Ridgeway and Sons). B36BEN01PAUS.

  • Britton, N. L. and A. B. Brown. 1913. An Illustrated Flora of the Northern United States, Canada, and the British Possessions. 2nd Edition in 3 Volumes. Charles Scribner's Sons, New York. B13BRI01PAUS.

  • Britton, N. L. and A. Brown. 1913. An Illustrated Flora of the Northern United States and Canada. 3 vol. Dover Publications, Inc., N. Y. 2052 pp.

  • Chambers, H.L, and K.L. Chambers. 1971. Artificial and natural hybrids in Pycnanthemum (Labiatae). Brittonia 23:71-88.

  • Chambers, H.L. 1961. Chromosome numbers and breeding systems in Pycnanthemum (Labiatae). Brittonia 13: 116-128.

  • Clemants, Steven and Carol Gracie. 2006. Wildflowers in the Field and Forest. A Field Guide to the Northeastern United States. Oxford University Press, New York, NY. 445 pp.

  • Connecticut Natural Diversity Database (CT NDD). 1994a. Element ocurrence records for Pycnanthemum clinopodioides and P. torrei. 8 pp.

  • Connecticut Natural Diversity Database (CT NDD). 1994b. State element ranking form for Pycnanthemum torrei. 1 p.

  • Connecticut Natural Diversity Database (CT NDD). 1994c. Field collection data sheets with map for Pycnanthemum torrei. 1 p.

  • Connecticut Natural Diversity Database (CT NDD). 1994d. Label information from herbarium specimens (NY) for Pycnanthemum torrei. 1 p.

  • Delaware Natural Heritage Program (DE NHP). 1993. Rare native plants of Delaware. Department of Natural Resources and Environmental Control, Division of Parks and Recreation.

  • Fernald, M. L. 1950. Gray's manual of botany. 8th edition. Corrected printing (1970). D. Van Nostrand Company, New York. 1632 pp.

  • Fernald, M.L. 1949. Gray's Manual of Botany, Eighth edition. American Book Co. New York. B49FER01PAUS

  • Fernald, M.L. 1950. Gray's Manual of Botany, 8th ed., Corr. Printing, 1970. Van Nostrand, New York. LXIV+1632 pp.

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  • Fernald, M.L. 1970. Gray's manual of botany. 8th edition. 1970 printing with corrections by R.C. Rollins [of 1950 8th edition]. D. Van Nostrand Company, New York.

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