Pinus elliottii
(slash pine)

Preferred Scientific Name

• Pinus elliottii Engelm.

Preferred Common Name

• slash pine

Variety

• Pinus elliottii var. densa Little & Dorman
• Pinus elliottii var. elliottii

Other Scientific Names

• Pinus heterophylla

International Common Names

• English: swamp pine
• Spanish: pino amarillo; pino macho
• French: pin d'Elliott
• Chinese: shi di song

Local Common Names

• Brazil: pinheiro
• Germany: Elliotts Kiefer
• Italy: pino di Elliott
• South Africa: basden
• USA: Cuban pine; longleaf pitch pine; pitch pine; swamp pine; yellow slash pine

EPPO code

• PIUEL (Pinus elliottii)

Trade name

• American pitch pine
• slash pine
• yellow pine

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Gymnospermae
•                 Class: Pinopsida
•                     Family: Pinaceae
•                         Genus: Pinus
•                             Species: Pinus elliottii

The genus Pinus was first classified on evolutionary characteristics by Shaw (1914), and most taxonomists have since followed his general separation of the genus into two groups: section/subgenus Haploxylon or Strobus, and Diploxylon or Pinus, commonly called the "soft" (or "white") and "hard" pines, respectively. This division is based on the presence of one or two vascular bundles in the leaves, respectively. Shaw's original subdivision of these groups has been reworked by different authorities (e.g., Pilger, 1926; Duffield, 1952; Ferre, 1965; Landry, 1974, 1978), but botanists in recent years have generally recognized the classification described by Little and Critchfield (Little and Critchfield, 1969; Critchfield, 1986), who recognize three subgenera: (1) Ducampopinus (one species: P. krempfii), (2) Strobus and (3) Pinus. 

Pinus elliottii belongs to subgenus Pinus, section Australes. Leaves in this group occur in groups of 2-3 in fascicles, with biform hypodermis, endodermis with a thin outer cell wall, and with internal resin ducts (Little and Critchfield, 1969). There are two varieties of P. elliottii: the typical variety (var. elliottii) and the South Florida slash pine (var. densa).

Stephen Elliott in 1824 was the first botanist to distinguish slash pine, naming it P. taeda var. heterophylla. In a revision of the genus Pinus, George Engelmann (1880) published a detailed description of the new species, naming it P. elliottii in honour of Elliott, whose name for it was cited as a synonym. The name P. elliottii was, however, short-lived, with slash pine being named P. caribaea, P. palustris, P. cubensis and P. heterophylla at various times and by various authors. A study by Little and Dorman (1952) ended the confusion and showed that the hard pines with shiny brown cones generally classified as P. caribaea were in fact three geographically separated taxa, viz. P. caribaea with a tropical distribution in the West Indies and Central America, and P. elliottii vars. elliottii and densa from the southeastern USA and southern Florida, respectively.

The common name slash pine is derived from the local name ‘slash’ given to the overgrown swamps that were its original habitat.

P. elliottii var. densa differs in a number of ways from var. elliottii (Little and Dorman, 1954); it is characterized by a grass-like, almost stemless stage that lasts for 2 to 6 years. It has a restricted range, a less desirable tree form than var. elliottii, and is more difficult to regenerate. As a result, almost all information available relates to var. elliottii.

P. elliottii var. elliottii trees range from 18 to 30 m in height and average about 0.6 m in diameter. Large trees are sometimes 36 m tall and 0.9 m in diameter. The trunk is straight and erect with a long clear bole. Self-pruning of the branches is common and results in a relatively short, narrow, ovoid crown with spreading and ascending limbs. P. elliottii develops an extensive lateral root system and a moderate taproot. Maximum length of the lateral roots may be double the tree height.

The needles are 18 to 25 cm long in fascicles of 2 and 3 on the same tree, dark glossy green, and tufted at the ends of tapering branches. They extend back some distance along the branch and are persistent until the end of the second season. Resin canals number 2 to 10 and are mostly internal. The fascicle sheath is usually 1.25 cm or less in length.

P. elliottii is monoecious and wind pollinated. The cones are 10 to 15 cm in length, ovoid-conic, and sessile. They usually persist on the tree until the following summer. Cones are reddish brown, lustrous, and are armed with a sharp spine. Seeds are about 0.6 cm long, dark brown mottled with black, with wings about 2.5 cm long that are thin and translucent. 

The naturalized range of P. elliottii has been extended by planting into northern Alabama, Georgia, southern Tennessee and western Louisiana. It was introduced into Kentucky, Virginia and eastern Texas in the 1900s. It now regenerates naturally in these areas.

Of the Pinus species introduced and tested for timber production in the Hawaiian Islands in the 20th century, P. elliottii has been one of the few to thrive in the warm climate and exists in forest reserves on six of the islands, most significantly on Kauai and Molokai; in the latter case, 52,000 trees were planted there between 1954 and 1960 (Skolmen, 1980). Naturalized populations are known in the native forests near the original plantings on Kauai, Molokai and Oahu (Evenhuis and Eldredge, 2012).

In South Africa, P. elliottii has been grown as a commercial forest species in the Eastern Transvaal zone since the 1920s (Darrow, 1992).

In Australia, trials of conifers in infertile coastal lowlands of south-east Queensland were initiated in the 1920s (Nikles, 1996). P. elliottii was introduced to New South Wales in 1921 and to Queensland in 1925, with large scale plantings in Queensland north of Brisbane in the 1930s. Self-sown trees were observed soon after, but were first documented in the 1960s (Richardson and Higgins, 1998).

Seed of P. elliottii was first introduced to Brazil in 1936 by the Instituto Florestal in São Paulo, with large scale plantations being established and investigated for forestry potential in the south of the country in 1955. Due to its ease of management and fast growth, it was used in large reforestation programmes with P. taeda between 1955 and 1964 (Bracelpa, 2010). Subsequently, invasions of P. elliottii have occurred into grassland savannahs, wetlands and coastal dune systems.

Soil drainage

• free
• impeded
• seasonally waterlogged

Soil reaction

• acid

Soil texture

• heavy
• light
• medium

Special soil tolerances

• infertile
• shallow

Natural Dispersal

Being winged, seeds are mostly spread short distances by wind (Queensland Government, 2011); over 90% fall within 45 m of the source tree (Cooper, 1957).

Vector Transmission

In Australia, Richardson and Higgins (1998) report that dispersal of slash pine cones by the glossy black cockatoo (Calyptorhynchus lathami) has aided the tree's spread into Eucalyptus forests.

Intentional Introduction

As an important forest tree, P. elliottii continues to be introduced to new areas for forestry purposes. 

Impact on Habitats

P. elliottii is classed as a Category 2 invasive species in South Africa, being a particular problem in Mpumalanga Province. Dense stands reduce water runoff and stream flow from mountain catchments, compete with native species, reduce grazing and pose a fire hazard (Invasive Species South Africa, 2015).

Studies have been carried out into P. elliottii invasions into grassland savannahs, wetlands and coastal dune systems in Brazil. Zenni and Ziller (2011) found it to be one of the most pervasive and aggressive invaders of subtropical ombrophilous forest and savannah. In coastal dunes in Florianópolis in Santa Catarina state, P. elliottii seed rain was observed to be continuous throughout the year, generating about 2 million viable seeds/ha annually which compensated for the lack of a soil seedbank. A 90% germination rate and a dense, permanent seedling bank contributed to the pine’s high level of invasiveness (Bechara et al., 2013, 2014). Abreu and Durigan (2011) observed that invasion by P. elliottii was one of the most serious threats to the remaining cerrado vegetation in São Paulo state. In one area, 22 years after the arrival of the first founding trees the savannah had become a dense pine forest, causing severe loss of native biodiversity.

In Argentina, P. elliottii has been observed invading overgrazed natural grasslands and other disturbed areas in Entre Rios, Corrientes and Misiones provinces, while in Queensland, Australia, the species has invaded heathland and open eucalypt forests (Richardson and Higgins, 1998).

Impact on Biodiversity

P. elliottii is a fast-growing tree that establishes dense stands that shade out native plants and prevent their regeneration. Invaded grasslands are transformed over time into species-poor shrublands and forests (Weber, 2003).

In Hawaii Poa mannii, a federally listed endangered endemic grass growing only on the island of Kauai, is threatened by loss and modification of habitat by alien invasive species such as P. elliottii. When it was listed in 1994, only four populations were known, containing a total of approximately 125 individuals (US Fish and Wildlife Service, 1994). From observations between 1991 and 2008, at least 13 populations are now known, with at least 100 individuals (US Fish and Wildlife Service, 2010).

P. mannii is one of three native Poa species in the Hawaiian Islands, all endemic to Kauai. It typically grows on moist vertical cliff faces or dripping, wet rock faces often on northern exposures in partial shade in lowland or montane diverse mixed mesic Metrosideros polymorpha or Acacia koa–M. polymorpha forests or shrubland at elevations of 327-1222 m (US Fish and Wildlife Service, 2003). Although described as a perennial, P. mannii appears to die back each year, with few rhizomes surviving to the following year. During this dieback period, several invasive introduced plant species have been known to overtake its cliff habitat (US Fish and Wildlife Service, 1994), competition from alien invasives, especially Erigeron karvinskianus and Lantana camara, but including P. elliottii, being a leading threat to the species’ survival. To reduce the threat to P. mannii, over 600 seeds were collected and stored, but no propagation had been carried out by 2010, and no plans for ecosystem-level restoration and management of habitats had been drawn up (US Fish and Wildlife Service, 2010).

Rolon et al. (2011) found that in the coastal plain of Rio Grande do Sul in southern Brazil, macrophyte species richness in ponds was reduced in areas invaded by P. elliottii.

• Proved invasive outside its native range
• Abundant in its native range
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Benefits from human association (i.e. it is a human commensal)
• Long lived
• Has high reproductive potential
• Has propagules that can remain viable for more than one year

• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Modification of fire regime
• Modification of hydrology
• Monoculture formation
• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species

• Competition - monopolizing resources
• Competition - shading

• Highly likely to be transported internationally deliberately

Economic Value

Slash pine is an important source of timber and wood pulp. Many of the products of P. elliottii forests are used in international trade. These range from solid wood products to kraft paper. The sapwood of P. elliottii is a yellowish white, while the heartwood is a reddish brown. The wood is very strong and heavy, very stiff, hard and moderately high in shock resistance. It has straight grain, is medium in texture and relatively difficult to work with hand tools (Alden, 1997). It is used for products such as sawlogs, veneer logs, poles, piling, posts, pulpwood, particleboard and chip-n-saw logs. The straightness of the bole makes P. elliottii particularly suited for poles, piling and solid wood products. Due to its rapid early growth it is also well suited for pulpwood rotations where paper is the final product. P. elliottii also yields the best quality and highest quantity of commercial turpentine of all American pitch pines (Streets, 1962).

Social Benefit

P. elliottii is also grown for its ornamental value and as a street tree. The species has been frequently used in agroforestry situations.

Environmental Services

Slash pines provide habitat and food for birds and small mammals, and are an important component of many natural communities (Hill, 2001). P. elliottii trees can be planted to stabilize the soil on eroding slopes and strip mine spoil banks.