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Tsuga caroliniana

Engelm.

Carolina Hemlock

G3Vulnerable Found in 15 roadless areas NatureServe Explorer →
G3VulnerableGlobal Rank
Near threatenedIUCN
HighThreat Impact
Carolina Hemlock (Tsuga caroliniana). Photo by Nate Martineau, CC BY-NC 4.0, via iNaturalist.
Nate Martineau, CC BY-NC 4.0
Carolina Hemlock (Tsuga caroliniana). Photo by Nate Martineau, CC BY-NC 4.0, via iNaturalist.
Nate Martineau, CC BY-NC 4.0
Carolina Hemlock (Tsuga caroliniana). Photo by Nate Martineau, CC BY-NC 4.0, via iNaturalist.
Nate Martineau, CC BY-NC 4.0
Carolina Hemlock (Tsuga caroliniana). Photo by Nate Martineau, CC BY-NC 4.0, via iNaturalist.
Nate Martineau, CC BY-NC 4.0
Carolina Hemlock (Tsuga caroliniana). Photo by Nate Martineau, CC BY-NC 4.0, via iNaturalist.
Nate Martineau, CC BY-NC 4.0
Carolina Hemlock (Tsuga caroliniana). Photo by Nate Martineau, CC BY-NC 4.0, via iNaturalist.
Nate Martineau, CC BY-NC 4.0
Identity
Unique IDELEMENT_GLOBAL.2.145577
Element CodePGPIN06020
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
IUCNNear threatened
Endemicendemic to a single nation
KingdomPlantae
PhylumConiferophyta
ClassPinopsida
OrderPinales
FamilyPinaceae
GenusTsuga
Other Common Names
Carolina hemlock (EN)
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.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2024-02-06
Change Date2023-11-15
Edition Date2024-02-15
Edition AuthorsBroaddus, Lynn, rev. C. Thurman (1991), rev. C. Nordman (2018, 2023), rev. Eberly (2024), rev. SE Ranking Workshop (2024)
Threat ImpactHigh
Range Extent20,000-200,000 square km (about 8000-80,000 square miles)
Number of Occurrences81 - 300
Rank Reasons
Carolina Hemlock (Tsuga caroliniana) is a long-lived but slow to mature evergreen conifer tree of the eastern United States, where it is endemic to the Southern Appalachians in western areas of Virginia (north to Rockbridge County), east Tennessee, western North Carolina, northwestern South Carolina, and north Georgia. There are estimated to be more than 200 occurrences, in open woodlands on mountain slopes, and rocky ridges. This tree has declined and continues to be highly threatened by the Hemlock Wooly Adelgid. Recovery of this species after invasion is concerning as the species is slow to mature.
Range Extent Comments
Carolina Hemlock (Tsuga caroliniana) occurs in eastern United States, where it is endemic to the southern Appalachian Mountains and western Piedmont, in western areas of Virginia (north to Rockbridge County), east Tennessee, western North Carolina, northwestern South Carolina, and north Georgia. Range extent was estimated to be between 35,000 and 50,000 square kilometers, using herbarium specimens, photo-based observations, and NatureServe Network occurrence data collected between 1992 and 2023 (Flora of North America Editorial Committee 1993, GBIF 2023, iNaturalist 2023, NatureServe 2023, SEINet 2023, Weakley and Southeastern Flora Team 2023).
Occurrences Comments
By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1992 and 2023, it is estimated that there are more than 200 occurrences of Carolina Hemlock, rangewide (GBIF 2023, iNaturalist 2023, NatureServe 2023, SEINet 2023). It is very rare in north Georgia, and more widespread in the mountains of western North Carolina, northwestern South Carolina, northeast Tennessee, and southwestern Virginia. Due to the rugged and remote areas where this tree grows, many occurrences are not represented by museum specimens.
Threat Impact Comments
The Hemlock Wooly Adelgid (Adelges tsugae) is affecting many populations of this tree. Trees in western North Carolina had about a 50% chance of survival 12 years after Hemlock Wooly Adelgid expanded into an area (Vogt et al. 2016). Degree of Hemlock Wooly Adelgid among occurrences varies throughout Carolina Hemlock's range: nearly all encountered trees in South Carolina have been impacted unless treated (Tessel, pers. comm., 2024) while only 30% of occurrences in Virginia note impacts (Townsend, pers. comm., 2024). Only treated trees are surviving in Georgia, and some evidence of hybridization with Tsuga canadensis has been documented, though the scope and severity of hybridization is unknown (Radcliffe, pers. comm., 2024). The displacement of T. caroliniana in the understory by shade tolerant maples is a concern for the regeneration of the species (Keyser et al. 2023), and seedlings have been observed infrequently in North Carolina (Schaner, pers. comm., 2024). Intense fires may negatively impact populations, and long-term impacts from the 2019 and 2023 wildfires in Linville Gorge, North Carolina are unknown (Schaner, pers. comm., 2024). Fire, increased temperatures, and drought may threaten this species.
Ecology & Habitat

Diagnostic Characteristics

Leaves of Carolina Hemlock are 10-18 mm long (leaves of Eastern Hemlock are 8-13 mm long), spreading distichously, plus leaves borne on the upper surface of the twig not appressed, spreading at a 60-90 degree angle from the twig, mostly 8-15 mm long, 3/4 to fully as long as the adjacent lateral leaves, seed cones 20-38 mm long, while the seed cones of Eastern Hemlock are 12-25 mm long (Weakley and Southeastern Flora Team 2023).

Habitat

Carolina Hemlock inhabits open woodlands on rocky montane slopes, on dry and exposed sites, such as rocky ridges overlain by acidic, sandy clay loam soils, at 700 - 1200 meters elevation (Flora of North America Editorial Committee 1993, Jetton et al. 2008, Levy and Walker 2014, Weakley and Southeastern Flora Team 2023).

Ecology

Tsuga caroliniana is a obligate climax species that highly tolerant of shade (Coladonato 1993) and nutrient and moisture stresses (Humphrey 1989).
Terrestrial Habitats
Forest/WoodlandWoodland - ConiferWoodland - Mixed
Other Nations (1)
United StatesN3
ProvinceRankNative
TennesseeS3Yes
North CarolinaS2Yes
South CarolinaS2Yes
GeorgiaS1Yes
VirginiaS2Yes
Threat Assessments
ThreatScopeSeverityTiming
7 - Natural system modificationsSmall (1-10%)Moderate or 11-30% pop. declineHigh (continuing)
7.1 - Fire & fire suppressionSmall (1-10%)Moderate or 11-30% pop. declineHigh (continuing)
8 - Invasive & other problematic species, genes & diseasesLarge (31-70%)Serious or 31-70% pop. declineHigh (continuing)
8.1 - Invasive non-native/alien species/diseasesLarge (31-70%)Serious or 31-70% pop. declineHigh (continuing)
8.3 - Introduced genetic materialUnknownUnknownUnknown
11 - Climate change & severe weatherRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
11.1 - Habitat shifting & alterationRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)

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Plant Characteristics
DurationLong-lived, EVERGREEN
Economic Value (Genus)No
Roadless Areas (15)
North Carolina (10)
AreaForestAcres
Balsam ConePisgah National Forest10,591
Dobson KnobPisgah National Forest6,111
Harper CreekPisgah National Forest7,325
Jarrett CreekPisgah National Forest7,485
Laurel MountainPisgah National Forest5,683
Linville Gorge AdditionPisgah National Forest2,809
Lost CovePisgah National Forest5,944
Mackey MountainPisgah National Forest5,934
Wilson CreekPisgah National Forest4,863
Woods MountainPisgah National Forest9,602
Virginia (5)
AreaForestAcres
Brush MountainJefferson National Forest6,002
Brush Mountain EastJefferson National Forest4,916
James River AdditionJefferson National Forest1,140
North MountainJefferson National Forest8,377
Raccoon BranchJefferson National Forest4,388
References (29)
  1. Abella, S.R. 2014. Impacts and Management of Hemlock Woolly Adelgid in National Parks of the Eastern United States. Southeastern Naturalist 13(6):16-45.
  2. Cohn, D'Vera. 1993. Shenandoah hemlocks under seige. Washington Post: September 4, 1993.
  3. Coladonato, M. 1993. <i>Tsuga caroliniana</i>. In: Fire Effects Information System. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Online. Available: https://www.fs.usda.gov/database/feis/plants/tree/tsucar/all.html (accessed 23 Jan 2024).
  4. Elias, T. S. 1980. The Complete Trees of North America Field Guide and Natural History. Van Nostrand Reinhold Co., New York, New York. 948 pp.
  5. Flora of North America Editorial Committee (FNA). 1993a. Flora of North America north of Mexico. Vol. 2. Pteridophytes and gymnosperms. Oxford Univ. Press, New York. xvi + 475 pp.
  6. Global Biodiversity Information Facility (GBIF). 2023. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2023).
  7. Havill, N.P., L.C. Vieira, and S.M. Salom. 2014. Biology and control of Hemlock Woolly Adelgid. Technology Transfer FHTET-2014-05. Washington, DC. 32 pp.
  8. Humphrey, L.D. 1989. Life history traits of <i>Tsuga caroliniana</i> Engelm. (Carolina hemlock) and its role in community dynamics. Castanea 54(3):172-190.
  9. iNaturalist. 2023. Online. Available: https://www.inaturalist.org (accessed 2023).
  10. Jetton, R. M., W. S. Dvorak, and W. A. Whittier. 2008. Ecological and genetic factors that define the natural distribution of Carolina hemlock in the southeastern United States and their role in <i>ex situ</i> conservation. Forest Ecology and Management 255:3212-3221.
  11. 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.
  12. Keyser, T.L., D.M. Styers, M. Wind, L. DeWald, and B. Collins. 2023. Composition and Structure of <i>Tsuga caroliniana</i> Engelm. Communities in the Southern Appalachian Mountains of Western North Carolina. Southeastern Naturalist 22(1):57-77.
  13. Levy, F. and E.S. Walker. 2014. Pattern and Rate of Decline of a Population of Carolina Hemlock (<i>Tsuga caroliniana</i> Engelm.) in North Carolina. Southeastern Naturalist 13(6):46–60.
  14. Little, E.L., Jr. 1971. Atlas of the United States trees. Vol. I. Conifers and important hardwoods. Miscellaneous Publication No. 1146. U.S. Forest Service, Washington, D.C. 200 pp.
  15. Little, E.L., Jr. 1979. Checklist of United States trees (native and naturalized). Agriculture Handbook No. 541. U.S. Forest Service, Washington, D.C. 375 pp.
  16. Mayfield, A.E. III, R.M. Jetton, B.T. Mudder, W.A. Whittier, T.L. Keyser, and J.R. Rhea. 2023. Silvicultural canopy gaps improve health and growth of eastern hemlocks infested with <i>Adelges tsugae</i> in the southern Appalachian Mountains. Forest Ecology and Management 546, 2023, 121374. DOI: https://doi.org/10.1016/j.foreco.2023.121374.
  17. Mayfield, A.E. III, T.D. Bittner, N.J. Dietschler, J.S. Elkinton, N.P. Havill, M.A. Keena, D.L. Mausel, J.R. Rhea, S.M. Salom, and M.C. Whitmore. 2023. Biological control of hemlock woolly adelgid in North America: History, status, and outlook. Biological Control 185 (105308). DOI: https://doi.org/10.1016/j.biocontrol.2023.105308. Online. Available: https://www.srs.fs.usda.gov/pubs/ja/2023/ja_2023_mayfield_001.pdf (Accessed 2023).
  18. NatureServe. 2023. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  19. Potter, K.M., A.R. Campbell, S.A. Josserand, C.D. Nelson, and R.M. Jetton. 2017. Population isolation results in unexpectedly high differentiation in Carolina hemlock (<i>Tsuga caroliniana</i>), an imperiled southern Appalachian endemic conifer. Tree Genetics &amp; Genomes 13:105.
  20. Radcliffe, Carrie. Personal Communication. Restoration Coordinator, Department of Science and Conservation, Atlanta Botanical Garden.
  21. Schaner, Jessica. Personal Communication. Western Regional Botanist, North Carolina Natural Heritage Program, Asheville, North Carolina.
  22. Southwest Environmental Information Network (SEINet). 2023. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2023).
  23. Tessel, Samantha. Personal communication. Upstate Botanist, South Carolina Department of Natural Resources, Heritage Trust Program, Clemson, SC.
  24. Townsend, J. Personal communication. Staff Botanist. Virginia Division of Natural Heritage. Department of Conservation and Recreation. Richmond, VA.
  25. U.S. Fish and Wildlife Service (USFWS). 2011. Endangered and threatened wildlife and plants; partial 90-day finding on a petition to list 404 species in the southeastern United States as threatened or endangered with critical habitat. Federal Register 76(187):59836-59862.
  26. U.S. Fish and Wildlife Service (USFWS). 2023. National Listing Workplan. Online. Available: https://www.fws.gov/project/national-listing-workplan
  27. Vogt, J.T., F.A. Roesch, M.J. Brown. 2016. Hemlock Woolly Adelgid (Adelges tsugae) and Hemlock (Tsuga spp.) in Western North Carolina: What do the Forest Inventory and Analysis Data Tell Us?. Southeastern Naturalist 15(4):631-645.
  28. Vose, J.M., D.N. Wear, A.E. Mayfield, and C.D. Nelson. 2013. Hemlock woolly adelgid in the southern Appalachians: Control strategies, ecological impacts, and potential management responses. Forest Ecology and Management 291: 209–219.
  29. Weakley, A.S., and Southeastern Flora Team. 2023. Flora of the southeastern United States. Edition of April 14, 2023. University of North Carolina Herbarium (NCU), North Carolina Botanical Garden, University of North Carolina, Chapel Hill. 2105 pp.