Pinus elliottii

Engelmann (1880)

Common names

Subsp. elliottii is slash pine, yellow slash pine, swamp pine; スラッシュマツ [Japanese].

Subsp. densa is the South Florida slash pine.

Taxonomic notes

There are two subspecies:

• Pinus elliottii subsp. densa (Little & K.W.Dorman) A.E.Murray. Type: USA, Florida, 20 miles (30 km) SE of La Belle, E. L. Little & K. W. Dorman 14033 (holotype US). Syn. P. elliottii var. densa Little & K.W.Dorman (1952), P. densa (Little & K.W.Dorman) de Laub. & Silba, P. densa (Little & K.W.Dorman) Silba var. austrokeysensis Silba 1990, P. elliottii subsp. austrokeysensis (Silba) Silba. Also, the name Pinus caribaea Morelet has been applied in error to P. elliottii var. densa
• Pinus elliottii subsp. elliottii. Type: USA, South Carolina, J. H. Mellichamp s.n., 1873.03.20 (lectotype MO). Syn. P. heterophylla (Elliott) Sudw. nom. illeg., P. taeda var. heterophylla Elliott.

None of the synonyms are in current use, except that the subspecies are commonly called varieties. However, the two taxa have clearly distinct morphologies, distinct distributions, and very distinct ecologies, particularly as regards fire adaptation. They do seem to be sister taxa, and they are sister to Pinus palustris within Pinus subsection Australes (Gernandt et al. 2018, Cruz-Nicolás et al. 2024). The two subspecies hybridize and introgression has occurred where their ranges are contiguous in central Florida (roughly 27.2° to 28.3°N); in this area it is difficult to distinguish between the two subspecies (Squillace 1966). Natural hybrids between P. elliottii and P. palustris have been observed; there have also been successful experimental crosses with P. glabra, P. resinosa, and P. rigida (Hardin 1971).

Description

Monoecious evergreen trees to 30 m tall and 80 cm dbh (occasionally larger), with a straight to contorted bole and a conical crown of spreading and ascending branches that becomes rounded or flattened with age. Bark orange- to purple-brown, irregularly furrowed and cross-checked into large, irregularly rectangular, papery-scaly plates; subsp. elliottii in particular has strikingly colored plates that exfoliate to expose the brightly colored bark beneath. Twigs stout (ca. 10 mm thick), orange-brown, aging darker brown, rough-scaly. Buds cylindric, silvery brown, 15-20 mm long; bud scale margins fringed. Leaves 2 or 3 per fascicle, spreading or ascending, persisting ca. 2 years, 15-20(-23) cm × 1.2-1.5 mm, straight, slightly twisted, pliant, yellow- to blue-green, all surfaces with stomatal lines, margins finely serrulate, apex abruptly acute to acuminate; sheath 1-2 cm, base persistent. Pollen cones cylindric, 30-40 mm long, purplish at maturity. Seed cones maturing in 2 years, falling the year after seed is shed, single or paired, symmetric, lance-ovoid before opening, ovoid or ovoid-cylindric when open, (7-)9-18(-20) cm long, light chocolate brown, on stalks to 3 cm long; apophyses lustrous (as if varnished), slightly raised, strongly cross-keeled; umbo central, depressed-pyramidal, with short, stout prickle. Seeds ellipsoid, oblique-tipped; body 6-7 mm, dark brown; wing to 20 mm (Kral 1993). See García Esteban et al. (2004) for a detailed characterization of the wood anatomy.

Like its close relative P. palustris, P. elliottii has strikingly long needles and thick twigs compared to other pines within its range. Over the large area where P. palustris may occur with P. elliottii subsp. elliottii, the two species are clearly distinguished by their seed cones; those of P. palustris have fewer, larger, thicker, and more woody scales. Also, P. palustris occurs on drier sites and shows a relative indifference to wind; P. elliottii is much more easily broken by severe windstorms.

As for the subspecies, subsp. elliottii has seedlings with erect, slender, pencil-like stems and scattered buds. The needles are commonly in fascicles of 3 although both 2- and 3-needled fascicles can be found on most trees; and opened seed cones are usually flattened at the base. Subsp. densa has seedlings with a grass stage (see P. palustris for full discussion), and the saplings also resemble P. palustris in growth form; the fascicles are predominantly 2-needled; the opened seed cones usually have a rounded base (Hardin 1971). The wood is denser and the plant has a thicker, deeper taproot compared to subsp. elliottii (Carey 1992).

Regarding life history, germination normally occurs within 2 weeks of seedfall, and is best on exposed mineral soil (e.g., after fire). The seeds have good viability. Open-grown seedlings of subsp. elliottii grow 40 cm in the first year and maintain good growth through the sapling stage, producing cones at between 10 and 15 years of age. Good cone crops occur every 3 years. In subsp. densa, seedlings begin in a grass stage that lasts 2 to 6 years during which time there is negligible height growth but substantial taproot development; perhaps as a result, these saplings are more tolerant of both floods and drought compared to subsp. elliottii. If top-kill occurs at this stage, the seedlings can resprout from the root collar. Once well established, rapid height growth begins and trees produce cones when 10-15 years old. Good cone crops occur every 4 years (Carey 1992). In both subspecies, trees are effectively mature by age 30, and continued vigorous growth beyond this point requires maintaining a suitable disturbance regime, typically involving low- to moderate-severity fire at intervals of at most 30 years, typically much less (Lohrey and Kossuth 1990, Carey 1992).

Distribution and Ecology

Subsp. elliottii occurs in the United States: Alabama, Louisiana, Florida, Georgia, Mississippi, South Carolina. Introduced populations have naturalized within this range, and it has also naturalized in east Texas (Carey 1992). Slash pine has also been introduced in subtropical and warm temperate areas worldwide (Kral 1993), and has naturalized in some areas. In South Africa, it is cultivated for timber, and has invaded forest margins and grassland in Mpumalanga. It has also invaded lower-altitude, higher-rainfall areas in Zimbabwe (Palgrave 2002). In the U.S. it is found in areas with a subtropical humid summer-wet climate that experiences about 1400 mm rainfall per year. Winter frosts occur, but rarely. Slash pine primarily grows in wetlands, usually on sand soils, often in areas that experience prolonged non-growing-season inundation; but it does not occur in mucks or other areas where it would be exposed to anoxic soils. Occurence is at 0-150 m elevation in lowland to upland forests, old fields, and pine flatwoods habitats, typically in pure stands or mixed with other pines such as P. taeda and P. serotina; other conifers include Chamaecyparis thyoides and Taxodium distichum (both varieties), as well as angiosperms such as Nyssa aquatica, N. sylvatica, Magnolia virginiana, and Persea borbonia (Farjon 2010). The predominant stand-destroying disturbances, apart from logging, are fires and windstorms (hurricanes). The species is early-seral, usually occupying a site in the aftermath of a stand-destroying disturbance. In the absence of such disturbance, slash pine flatwoods are replaced by southern mixed hardwood forests on drier sites and by bayhead swamps on wetter sites (Carey 1992). See also Thompson et al. (1999).

Slash pine has an extremely large area of occurrence and area of occupancy, with many discrete populations; accordingly it is of "least concern" for conservation.

Distribution data from USGS (1999).

Subsp. densa is endemic to the United States: Florida. It experiences a warmer climate than subsp. elliottii, with about 1440 mm annual precipitation with a June-September maximum, an average January minimum temperature of 13.6°C, and an average August maximum of 33.2°C (PRISM Climate Group 2025); this means summer maximum temperatures are about the same, but winter minima about 10°C warmer, compared to subsp. elliottii. Subsp. densa grows at 0-10(-20) m elevation in pine rocklands and flatwoods, mostly over limestone (Kral 1993). It commonly occurs at the lowest possible elevations, transitioning to brackish glades or more salt-tolerant mangroves at the lower elevation limit. There really is no upper elevation limit; almost none of its range has elevations above 10 m. Typically it occurs in pure stands. Zone 10 (cold hardiness limit between -1°C and +4.4°C) (Bannister and Neuner 2001). Its characteristic habitat is pine rocklands, where the substrate is limestone. At higher elevations the pine rocklands have virtually been extirpated because they represent desirable sites for residential development, but in the Everglades National Park and parts of the Keys, they are at very low elevations and large areas have been protected. These habitats are subject to frequent and prolonged flooding, especially in response to tropical storms, and the associated intrusion of salt water is a primary cause of mortality among the pines (Harley et al. 2015). Wiregrass (Aristida beyrichiana) is the dominant grass, and common shrubs include saw palmetto (Serenoa repens) as well as Lyonia lucida, Lyonia fruticosa, Ilex glabra, Vaccinium darrowii, Vaccinium myrsinites, and Quercus minima (Huffman and Judd 1998). The pine community is maintained by frequent low-intensity fire, historically occurring in response to summer thunderstorms, which are frequent and characterized by abundant lightning. Seedlings as young as 2 years will survive a typical fire, and historic fire frequencies recurred on the average every 1 to 3 years (Wade et al. 1980, FNAI 2010). When I visited the Everglades and Big Cypress areas in 2024 it was clear that prescribed fire is being used to manage these communities on a large scale, such that large areas had been burned that very year.

In 2011 the IUCN assessed South Florida slash pine as "near threatened" based on a restricted area of occurrence and area of occupancy, as well as substantial range reductions due to loss of habitat as a result of development and changing land uses. It is also threatened by hybridization with plantations of subsp. elliottii planted within its range, and substantial numbers of trees have also been lost to the pathogenic fungus Cronartium quercuum (Farjon 2013).

Pests and pathogens afflicting slash pine (both subspecies) include, most importantly, fusiform rust caused by the fungus Cronartium quercuum f. sp. fusiforme. Most of the southern oaks serve as alternate hosts but the fungus damages only pines; many trees are killed or deformed. Site treatments such as fertilization or vegetation control increase susceptibility to the disease. Resistance to the fungus is inherited, and attempts are being made to breed resistant strains. Another fungal disease is Annosus root rot, caused by the fungus Heterobasidion annosum. It is most damaging on soils with good drainage and is not a problem in flatwoods. Infections begin when spores germinate on a fresh stump surface; the fungus then spreads to adjacent trees through root contact. Diseased or dead and dying trees are usually found in groups. The fungus Fusarium subglutinans causes pitch canker; this is mainly an issue with cultivated trees. Cankers below the crown may eventually girdle the trunk and kill the tree. Conversely, there are few insect pests that have the potential to cause serious damage. The pales weevil (Hylobius pales) invades logged areas, feeds on the bark of seedlings, and may girdle the stem, causing wilting and eventual death. Small trees cat be defoliated by the pine webworm (Pococera robustella), blackheaded pine sawfly (Neodiprion excitans), redheaded pine sawfly (N. lecontei), and Texas leafcutting ant (Atta texana). The black turpentine beetle (Dendroctonus terebrans) and engraver beetles (Ips spp.) can also become problems (Lohrey and Kossuth 1990).

Remarkable Specimens

The largest specimen is in subsp. elliottii: 129 cm dbh, 27.7 m tall, crown spread 19.5 m, located in Virginia City, Virginia (an ornamental specimen planted outside its native range) (Payne 2025). A substantially taller tree (also subsp. elliottii) is reported in Nannup, Western Australia: 84 cm dbh and 37 m tall with a 12 m crown spread (National Register of Big Trees 2025). The largest of subsp. densa has dbh 105 cm, height 20 m, crown spread 23 m, located at the University of South Florida, Sarasota, Florida (American Forests 1996).

The oldest trees are in subsp. densa. They have all been found at Big Pine Key, where they have endured many hurricanes and fires. The oldest record is a living tree established in 1757 that was 257 years old when sampled (Harley et al. 2015).

Ethnobotany

Aboriginal use of Pinus elliottii is recorded for the Seminole people, who occupied lands within the range of both subspecies. Medicinal uses focused on decoctions of the wood and bark that were used to treat sores and rheumatism, and as an analgesic. The plant was used, in unspecified ways, for basketry, house construction, furniture construction, and to make poles used in a ball game. The resins were used to make torches, glues, and in tanning (Native American Ethnobotany Database 2025).

Following Euroamerican settlement, slash pine exploitation got off to a slow start. Although the species has a wide range, from Louisiana to South Carolina, its area of occupancy was relatively small compared to other southern pines such as Pinus palustris and P. taeda. Although it was early exploited for timber production, and its resin collected for naval stores and related uses (as described in detail for longleaf pine, P. palustris), still exploitation rates did not exceed regrowth until about 1880. The advent of railroad logging, and the mechanization of sawmills, then enabled far more rapid exploitation, particularly in the period 1890-1914. This coincided with decimation of the longleaf pine forests and in much of the Gulf Coast area, the cutover longleaf pine stands were replanted to slash pine; this also happened to a lesser degree along the Atlantic coast. The reason was simply that slash pine is easier to regenerate, and grows to harvestable size more quickly, compared to longleaf pine. By 2004, slash pine (subsp. elliottii) was the primary pine on 10.4 million acres (4.16 million ha), most of it plantation forests located in Florida and Georgia (Barnett and Sheffield 2004). Slash pine has also been introduced to cultivation in Argentina, Australia, Brazil, Burundi, Chile, China, Madagascar, Malawi, Mauritius, New Zealand, Réunion, South Africa, Swaziland, Tanzania, Venezuela, Zambia, and Zimbabwe (Barnett and Sheffield 2004, Prota 2025); in Brazil, it is heavily exploited for both timber and production of gum rosin and turpentine, the latter amounting to over 150,000 tons per year (Rodriguez-Honda et al. 2023). See PROTA (2025) for information on wood properties.

Subsp. densa, in contrast, was not used for naval stores (Kral 1993). It is locally planted for timber production in south Florida. For example, it is planted for commercial uses by the U.S. Air Force land managers at Avon Park Bombing Range as well as by Lykes Brothers ranch in south central Florida, and seedlings are offered for sale by the Florida Division of Forestry (Jay Frost email 2009.07.04). Overall, though, its economic significance is far less than that of subsp. elliottii. Subsp. densa has also been used in dendrochronology. Exploratory work has been done, demonstrating that the species produces annual rings, chronology development is feasible, and that the trees are mainly responsive to variation in summer rainfall (Harley et al. 2011). The trees have been used in reconstructions of hurricane occurrence and wildfire frequency, as well as related ecological topics (Harley et al. 2012, 2016), as well as some rather unique things like a study of the effects of hurricane-driven salt spray on wood production (Grissino-Mayer et al. 2001).

Observations

Subsp. elliottii is abundant and picturesque on the barrier islands of the Florida panhandle; I particularly recommend the Fort Pickens area at Gulf Islands National Seashore and the forests at St. George Island State Park. These coastal sites are not particularly typical, though. Excellent examples of typical pine flatwoods can be found in Apalachicola National Forest, where I saw it in many areas along the Florida Trail. Be prepared to get your feet wet.

The Nature Conservancy's Tiger Creek Preserve north of Sebring is a good site to see trees that are transitional between subsp. elliottii and subsp. densa.

Subsp. densa can be seen to advantage at these four sites:

• The Okaloacoochee Slough Wildlife Area is the headwaters of the "river of grass" that is the Everglades. Here the trees form a mosaic with wetland and scrub vegetation where both fire and hurricanes shape the forest over the long term.
• Long Pine Key in Everglades National Park is probably the easiest of all places to get to know the pine. The site is extensive, beautifully managed to have a natural fire regime and minimize invasive species, and has a good system of interpretive trails.
• Big Pine Key has one of the strangest conifer forests I've seen. The trees are growing out of solid limestone, in a setting where floods, fire and rapid decay rates remove all nonliving organic matter. The trees are relatively ancient; a tree 10 m tall and 20 cm dbh may be well over 200 years old. Check out the interpretive trails at the Blue Hole and at the Watson Trail just north of there. Read Harley et al. (2015) for background on this ecosystem.
• Jonathan Dickinson State Park has a beautifully restored, absolutely classic pine flatwoods community. It also has saltwater intrusion converting riparian Taxodium forest to mangroves, a beautiful coastal scrub system with Pinus clausa, a good interpretive trail system, and an extraordinarily good interpretive center.

Remarks

The epithet honors botanist Stephen Elliott (1771-1830). The epithet densa refers to the wood, which is much heavier and harder compared to subsp. elliottii; and refers also to "the grasslike seedlings with crowded needles, very thick hypocotyl and thick taproot, and to the thick hypoderm of the needles" (Little and Dorman 1952).

Citations

American Forests 1996. The 1996-1997 National Register of Big Trees. Washington, DC: American Forests.

Barnett, James P. and Sheffield, Raymond M. 2004. Slash pine: characteristics, history, status and trends. In: Dickens, E. D., et al. (eds.), Slash Pine: still growing and growing! Proceedings of the slash pine symposium. USFS Gen. Tech. Report SRS-76. Asheville, NC: Southern Research Station.

Carey, Jennifer H. 1992. Pinus elliottii. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.usda.gov/database/feis/plants/tree/pinell/all.html, accessed 2025.03.12.

Cruz-Nicolás, Jorge, Juan Pablo Jaramillo-Correa, and David S. Gernandt. 2024. Stochastic processes and changes in evolutionary rate are associated with diversification in a lineage of tropical hard pines (Pinus). Molecular Phylogenetics and Evolution 192:108011, doi.org/10.1016/j.ympev.2024.108011.

Engelmann, George E. 1880. Revision of the genus Pinus, and description of Pinus Elliottii. Trans. Acad. Sci. St. Louis 4:161-190 (p. 186, plates 1-3). Available: Biodiversity Heritage Library, accessed 2024.11.22. Includes a splendid illustration.

Farjon, A. 2013. Pinus elliottii var. densa. The IUCN Red List of Threatened Species 2013: e.T18153818A18153821. https://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T18153818A18153821.en, accessed 2025.03.12.

Florida Natural Areas Inventory [FNAI]. 2010. Guide to the natural communities of Florida - Wet Flatwoods and Pine Rocklands accounts. https://www.fnai.org/species-communities/natcom-accounts, accessed 2025.03.12.

Gernandt, David S., Xitlali Aguirre Dugua, Alejandra Vázquez-Lobo, Ann Willyard, Alejandra Moreno Letelier, Jorge A. Pérez de la Rosa, Daniel Piñero, and Aaron Liston. 2018. Multi-Locus phylogenetics, lineage sorting, and reticulation in Pinus subsection Australes. American Journal of Botany 105(4):711–25. doi.org/10.1002/ajb2.1052.

Grissino-Mayer, H.D., Blount, H.C., Miller, A.C. 2001. Tree-ring dating and the ethnohistory of the naval stores industry in southern Georgia. Tree-Ring Research 57(1):3-13.

Hardin, J. W. 1971. Studies of the Southeastern United States Flora. II. The Gymnosperms. Journal of the Elisha Mitchell Scientific Society 87(2):43–50.

Harley, Grant L., Henri D. Grissino-Mayer, and Sally P. Horn. 2011. The dendrochronology of Pinus elliottii in the lower Florida Keys: chronology development and climate response. Tree-Ring Research 67(1):39-50.

Harley, Grant L., Henri D. Grissino-Mayer, and Sally P. Horn. 2012. Fire history and forest structure of an endangered subtropical ecosystem in the Florida Keys, USA. International Journal of Wildland Fire 22(3):394. https://doi.org/10.1071/WF12071.

Harley, G., Maxwell, J., and Raber, G. 2015. Elevation promotes long-term survival of Pinus elliottii var. densa, a foundation species of the endangered pine rockland ecosystem in the Florida Keys. Endangered Species Research 29(2):117–130. https://doi.org/10.3354/esr00707.

Huffman, J. M., and W. S. Judd. 1998. Vascular flora of Myakka River State Park, Sarasota and Manatee counties, Florida. Castanea 63:25-50.

Little, Elbert L., Jr., and Keith W. Dorman. 1952. Slash pine (Pinus elliottii), its nomenclature and varieties. Journal of Forestry 50: 918-923.

Lohrey, R. E. and S. V. Kossuth. 1990. Pinus elliottii Engelm. Slash pine. In Burns and Honkala (1990).

National Register of Big Trees. 2025. https://www.nationalregisterofbigtrees.com.au/editorfiles/file/tree_trivia_details_2022.pdf, accessed 2025.03.12.

Native American Ethnobotany Database. 2025. Results of search for "Pinus elliottii". Available: http://naeb.brit.org/uses/search/?string=pinus+elliottii, accessed 2025.03.12.

Payne, J. (ed.). 2025. The 2024 Register of National Champion Trees. National Champion Tree Program, https://nationalchampiontree.org/.

PRISM Climate Group. 2025. 30-Year Normals (1991-2020) for 30.8961°N, 87.6238° W. https://prism.oregonstate.edu/normals/, accessed 2025.03.03.

PROTA. Pinus elliottii Engelm. https://prota.prota4u.org/protav8.asp?h=M4&t=Pinus,elliottii&p=Pinus+elliottii, accessed 2025.03.12.

Rodrigues-Honda, K.C.d.S.; Junkes, C.F.d.O.; et al. 2023. Carbon sequestration in resin-tapped slash pine (Pinus elliottii Engelm.) subtropical plantations. Biology 12:324. https://doi.org/10.3390/biology12020324.

Squillace, A. E. 1964. Geographic Variation in Slash Pine. Dissertation, University of Florida. 56 p. Available: Biodiversity Heritage Library, accessed 2025.03.12.

Wade, D., J. Ewel, and R. Hofstetter. 1980. Fire in south Florida ecosystems. USFS General Technical Report SE-17. Asheville, NC: Southeastern Forest Experiment Station.

See also

FEIS database.

Huffman, J.M., W.J. Platt, H. Grissino-Mayer, and C.J. Boyce. 2004. Fire history of a barrier island slash pine (Pinus elliottii) savanna. Natural Areas Journal 24(3): 258-268.

Nelson, C. D., Nance, W. L. and Wagner, D. B. 1994. Chloroplast DNA variation among and within taxonomic varieties of Pinus caribaea and Pinus elliottii. Can. J. For Res. 24:424-426.

Nikles, D. G. 1966. Comparative variability and relationship of Caribbean Pine (Pinus caribaea Mor.) and Slash Pine (Pinus elliottii Engelm.). Ph.D. Thesis. NC State University. 201 pp.

Prasad and Iverson (1999).

Wagner, D. B., Nance, W. L., Nelson, C. D., Li, T., Patel, R. N. and Govindaraju, D. R. 1991. Taxonomic patterns and inheritance of chloroplast variation in a survey of Pinus echinata, Pinus elliottii, Pinus palustris, and Pinus taeda. Canadian Journal of Forest Research 22:683-689.