Pennisetum purpureum
(elephant grass)

Pictures

Picture	Title	Caption	Copyright
Title Habit Caption Pennisetum purpureum (elephant grass); habit - plant with inflorescences. Copyright ©Smithsonian Institution/Pedro Acevedo-Rodriguez	Habit	Pennisetum purpureum (elephant grass); habit - plant with inflorescences.	©Smithsonian Institution/Pedro Acevedo-Rodriguez
Title Habit and foliage Caption Pennisetum purpureum (elephant grass); habit and foliage. Copyright ©Smithsonian Institution/Pedro Acevedo-Rodriguez	Habit and foliage	Pennisetum purpureum (elephant grass); habit and foliage.	©Smithsonian Institution/Pedro Acevedo-Rodriguez
Title Habit Caption Roadside area in Puerto Rico infested by Pennisetum purpureum Copyright ©Smithsonian Institution/Pedro Acevedo-Rodriguez	Habit	Roadside area in Puerto Rico infested by Pennisetum purpureum	©Smithsonian Institution/Pedro Acevedo-Rodriguez
Title Inflorescence Caption Pennisetum purpureum (elephant grass); close-up of inflorescence. Copyright ©Smithsonian Institution/Pedro Acevedo-Rodriguez	Inflorescence	Pennisetum purpureum (elephant grass); close-up of inflorescence.	©Smithsonian Institution/Pedro Acevedo-Rodriguez
Title Inflorescence Caption Pennisetum purpureum (elephant grass); detail of inflorescence. Copyright ©Smithsonian Institution/Pedro Acevedo-Rodriguez	Inflorescence	Pennisetum purpureum (elephant grass); detail of inflorescence.	©Smithsonian Institution/Pedro Acevedo-Rodriguez

Identity

Preferred Scientific Name

• Pennisetum purpureum Schumach

Preferred Common Name

• elephant grass

Other Scientific Names

• Cenchrus purpureus (Schumach.) Morrone
• Gymnotrix nitens Andersson
• Pennisetum benthamii Steud.
• Pennisetum benthamii var. nudum Hack.
• Pennisetum benthamii var. sambesiense Hack.
• Pennisetum benthamii var. ternatum Hack.
• Pennisetum blepharideum Gilli
• Pennisetum flavicomum Leeke
• Pennisetum flexispica K. Schum
• Pennisetum gossweileri Stapf & C.E. Hubb.
• Pennisetum hainanense H.R.Zhao & A.T. Liu
• Pennisetum lachnorrhachis Peter
• Pennisetum nitens (Andersson) Hack.
• Pennisetum pallescens Leeke
• Pennisetum pruinosum Leeke
• Pennisetum purpureum subsp. benthamii (Steud.) Maire & Weiller
• Pennisetum purpureum subsp. flexispica (K.Schum.) Maire & Weiller

International Common Names

• English: cane grass; elephantgrass; merker grass; napier fodder; napier grass; napiergrass; Uganda grass
• Spanish: hierba elefante; pasto elefente; pasto Napier; yerba elefante; zacate elefante
• French: canne fourragère; fausse canne à sucre; Herbe a elephant; herbe éléphant; Sissongo; z'herbe éléphant
• Chinese: xiang cao
• Portuguese: capim-elefante

Local Common Names

• : mfufu
• Australia: barner grass; cane grass; merker grass
• Brazil: capim-cameroon; capim-camerron; capim-napier
• Colombia: elefante; elefante morado
• Cook Islands: 'erepani
• Costa Rica: pasto azul; pasto gigante
• Dominican Republic: árbol del pan; bufala; búfala; yerba merck; yerba mercury
• Germany: Elefantengras
• Italy: Erba elefantina; Penniseto rosso
• Japan: pokao
• Mexico: gigante; merkerón; zacante gigante
• Micronesia, Federated states of: acfucsracsracsr
• Palau: bokso
• Samoa: vao povi
• Vietnam: co voi

EPPO code

• PESPU (Pennisetum purpureum)

Summary of Invasiveness

P. purpureum is a robust perennial grass widely naturalized in tropical and subtropical regions of the world. This C₄ grass is included in the Global Compendium of Weeds where it is listed as an agricultural and environmental weed as well as an invasive species (Randall, 2012). P. purpureum is an aggressive grass that grows rapidly, colonizing new areas and forming dense thickets. Once established, it can change features of ecosystem functions by altering fire regimes, hydrology cycles, biophysical dynamics, nutrient cycles, and community composition (D’Antonio and Vitousek, 1992). P. purpureum is well adapted to drought conditions and can also dominate fire-adapted grassland communities (Holm et al., 1979). This species has the capability to resprout easily from small rhizomes left after disturbance, resulting in the out-competing and smothering of native plant communities (Holm et al., 1979; D’Antonio and Vitousek, 1992; Langeland et al., 2008). P. purpureum is considered one of the most successful invasive grasses in the world.

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Monocotyledonae
•                     Order: Cyperales
•                         Family: Poaceae
•                             Genus: Pennisetum
•                                 Species: Pennisetum purpureum

Notes on Taxonomy and Nomenclature

The genus Pennisetum is included in the subfamily Panicoideae of the Poaceae family. This is a large and variable genus, but the bristly, spike-like inflorescence is always readily recognizable. The only other panicoid genus with a similar bristly inflorescence is Setaria, but in that genus the bristles are not deciduous with the spikelets, instead remaining on the rachis at maturity. The bristles are derived from reduced panicle branches (Gould and Shaw, 1983; Gibson, 2009). The common name of elephant grass reflects it making up the bulk of the diet of forest elephants in West Africa (Francis, 1992).

Description

Robust perennial grass up to 4 metres tall; grows forming thick clumps or colonies from basal offshoots or short rhizomes. Stems often branched above; internodes more or less bluish glaucous; young nodes with white hairs, later becoming smooth, glabrous. Leaf sheaths glabrous, usually shorter than the internodes; ligule a narrow rim densely fringed with long white hairs. Leaf blades linear to tapering, flat, often bluish green, to 1 m long and 3 cm wide, pilose near the base, especially on margins; blade margins generally rough; midvein stout, whitish above, strongly keeled below. Inflorescence a dense terminal bristly spike, tawny to purple-tinged, to about 20 cm long and 2 cm wide. Spikelets 4-6 mm long, solitary or in clusters of 2-6 on hairy axis, surrounded by sparsely plumose bristles to 2 cm long that fall with the spikelets at maturity; outermost glume minute or absent (Langeland et al., 2008).

Plant Type

Distribution

P. purpureum is native to Tropical Africa and the sub-Saharan region (Clayton et al., 2013). It has been widely introduced into tropical and subtropical regions of the Old and New World where it commonly becomes naturalized, and in some cases invasive (see distribution table for details; Duke, 1983; Langeland et al., 2008; FAO, 2013).

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

P. purpureum has been intentionally introduced as a forage crop in many tropical and subtropical countries (Holm et al., 1979; Francis, 1992; FAO, 2013). It has been the subject of breeding for improved cultivars and hybrids for forage and silage (Tropical Forages, 2013). In the United States, this grass was introduced in 1913. It was established into natural areas of Florida by 1971 (Langeland et al., 2008). In the West Indies, Central and South America, many cultivars were introduced in the early 1950s. For example, the cultivar “Merkeron” was introduced in Puerto Rico in 1955 and in 1962 the cultivar “Capricorn was introduced in Australia (FAO, 2013; Tropical Forages, 2013).  

Risk of Introduction

The risk of introduction of P. purpureum is very high. This grass has been repeatedly intentionally introduced in tropical and subtropical regions to be used as a forage and silage crop. It has escaped from cultivation into natural areas, where it rapidly colonizes new areas forming dense stands which are very difficult to control (Langeland et al., 2008; Queensland Department of Primary Industries and Fisheries, 2011).

Habitat

P. purpureum is a common weed in agricultural fields, pastures, and along roadsides. It also grows in waterways, wetlands, floodplains, riverbanks, swamps, forest edges, disturbed sites, and waste ground especially in mesic to wet sites (Francis, 1992; Wagner et al., 1999; Langeland et al., 2008; Queensland Department of Primary Industries and Fisheries, 2011). P. purpureum is well-adapted to drought conditions and can be found colonizing arid lowlands (e.g., habitats on Galápagos Islands; McMullen, 1999).

Habitat List

Host Plants and Other Plants Affected

Biology and Ecology

Genetics

The chromosome number in P. purpureum is 2n = 27, 28, 56 (Sinha et al., 1990; Vidhya and Khna, 2003; Tropical Forages, 2013). There are numerous ecotypes grown for agriculture in various countries, and a range of commercial cultivars have been bred, including the widely grown cv. Mott bred in Georgia, USA from cv. Merkeron. A number of hybrids with Pennisetum glaucum are also commercially available. Tropical Forages (2013) lists important cultivars and hybrids used for forage and silage production. 

Reproductive Biology

P. purpureum relies on wind to achieve cross-pollination, due to asynchrony of male and female flower parts. However, this is also an apomictic species which can produce seed by this asexual method of reproduction (Brown and Emery, 1958; Stevens, 2012). The species is an inconsistent seed producer and in some habitats it rarely develops seeds, possibly due to low pollen viability (Tropical Forages, 2013). When seeds are produced they are dispersed by wind (Francis, 1992), but are often of low viability. 

Physiology and Phenology

P. purpureum is a fast-growing perennial grass (FAO, 2013). In Florida, P. purpureum produces flowers from July through February (Langeland et al., 2008). In Mexico and Central America, flowering occurs all year long with peaks from December to May (Vibrans, 2009). In South Africa this species flowers from January to June (Tropical Forages, 2013).

As many other C4 grasses, P. purpureum is well adapted to environments with high daytime temperatures, intense sunlight, drought and nitrogen and /or CO₂ limitations (Gibson, 2009). It grows during the rainy season, but its deep root system allows it to survive long drought periods. In an agricultural research plot in Puerto Rico, P. purpureum reached the height of 4 metres in just 3 months (Francis, 1992). 

Environmental Requirements

P. purpureum prefers to grow in moist tropical habitats at elevations from sea level to 2000 metres (Francis, 1992; FAO, 2013). It grows best in high-rainfall areas (>1500 mm/year), but its deep root system allows it to survive in dry times and it is reported to tolerates areas with annual precipitation of 200-4000 mm (Duke, 1983). It is well adapted to grow on a wide range of soil types from poorly drained clay soils to excessively drained sandy soils with pH ranging from 4.5 to 8.2, but grows best in rich well-drained soils (Duke, 1983; FAO, 2013; Tropical Forages, 2013). Temperatures for optimum growth should be from 25°C to 40°C, and there is little growth below about 15°C (FAO, 2013). It does not tolerate much frost. It recovers well following fire, and can dominate fire-adapted grassland communities (Tropical Forages, 2013). P. purpureum has the capability to grow in completely open sunlit areas to partially light-shaded areas but does not survive under a closed tree canopy (Francis, 1992; FAO, 2013).

Climate

Latitude/Altitude Ranges

Air Temperature

Rainfall

Rainfall Regime

Soil Tolerances

Soil drainage

• free
• seasonally waterlogged

Soil reaction

• acid
• alkaline
• neutral

Soil texture

• heavy
• light
• medium

Special soil tolerances

• shallow

Natural enemies

Means of Movement and Dispersal

P. purpureum reproduces sexually by seeds and also vegetatively by stem fragments, cuttings, and tillers. Seeds are dispersed by the wind, but they can also become attached to animals and vehicles. Seeds may also be spread as a contaminant of agricultural produce (i.e., fodder). Stem fragments and rhizomes may be broken off and dispersed to new locations by humans, wild animals, livestock, vehicles, and/or floodwaters. Seeds and stem fragments can also be spread by the movement of soil (Francis, 1992; Langeland et al., 2008; Queensland Department of Primary Industries and Fisheries, 2011; FAO, 2013).

Pathway Causes

Pathway Vectors

Impact Summary

Environmental Impact

P. purpureum is an aggressive grass that grows rapidly, colonizing new areas and forming dense thickets. It has the potential to alter fire regimes, hydrology cycles, biophysical dynamics, nutrient cycles, and community composition in invaded habitats (D’Antonio and Vitousek, 1992). P. purpureum is well adapted to drought conditions and can also dominate fire-adapted grassland communities. Consequently, it can completely out-compete native vegetation communities very rapidly. P. purpureum also creates problems in flood-control systems by blocking access to canals, reducing water flows, and overgrowing pump stations (Langeland et al., 2008; Queensland Department of Primary Industries and Fisheries, 2011).

Threatened Species

Risk and Impact Factors

• Invasive in its native range
• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Highly mobile locally
• Benefits from human association (i.e. it is a human commensal)
• Fast growing
• Has high reproductive potential
• Reproduces asexually

• Altered trophic level
• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Modification of fire regime
• Modification of hydrology
• Modification of nutrient regime
• Modification of successional patterns
• Monoculture formation
• Negatively impacts agriculture
• Reduced native biodiversity
• Threat to/ loss of native species

• Allelopathic
• Competition - monopolizing resources
• Competition - shading
• Competition - smothering
• Pest and disease transmission
• Rapid growth
• Rooting

• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately
• Difficult to identify/detect as a commodity contaminant
• Difficult/costly to control

Uses

P. purpureum is one of the most valuable forage and silage crops in its native Africa and throughout the wet tropics. It is an important forage and pasture grass especially for cattle and it is also cut for hay and fermented for silage (Francis, 1992; FAO, 2013). This grass is also planted as hedgerows for erosion protection and forage production in the alley cropping system of agroforestry (Magcale-Macandog et al., 1998). P. purpureum is also used as a windbreak in horticultural crops and orchards and lines of these plants are used to mark boundaries between plots and properties (FAO, 2013; Tropical Forages, 2013). In Africa, P. purpureum is planted on riverbanks to prevent erosion, and the thick culms are made into fences, screens, and reinforcement for mud huts (Francis, 1992). Plant extracts are used as a diuretic in Africa, and it is also used in a number of other herbal remedies (Francis, 1992).

Uses List

Animal feed, fodder, forage

• Fodder/animal feed
• Forage

Environmental

• Agroforestry
• Boundary, barrier or support
• Erosion control or dune stabilization
• Soil conservation
• Windbreak

General

• Ornamental

Materials

• Fibre
• Green manure

Similarities to Other Species/Conditions

P. purpureum is similar to Pennisetum polystachion (mission grass), Pennisetum macrourum (African feather grass), Pennisetum pedicellatum (Deenanth grass) and Pennisetum alopecuroides (swamp foxtail). It can usually be distinguished from these species by its perpendicular size, but can also be separated by the following characteristics:

1. P. purpureum is a very large and robust perennial grass (1-7 m tall) with greenish, yellowish or purplish coloured seed-heads. The main stem (i.e., rachis) of the seed-head is rounded and the bristles below each flower spikelet are relatively long (8-40 mm).
    
2. P. polystachion is a perennial grass (usually 2-3 m tall) with yellowish or brownish coloured seed-heads. The rachis of the seed-head is angular and the bristles below each flower spikelet are relatively long (4-25 mm long). P. purpureum is distinguished by its yellow or yellowish-brown bristles with or without purple tip, and its softer stem.
    
3. P. macrourum is a large perennial grass (usually 1-2 m tall) with greenish or yellowish coloured seed-heads. The rachis of the seed-head is rounded and the bristles below each flower spikelet are relatively short (mostly less than 10 mm long).
    
4. P. pedicellatum is a moderately-sized annual grass (usually 30-150 cm tall) with pale purplish coloured seed-heads. The rachis of the seed-head is angular and the bristles below each flower spikelet are relatively long (6-24 mm long).
    
5. P. alopecuroides is a moderately-sized perennial grass (usually 60-100 cm tall) with greenish or purplish coloured seed-heads. The rachis of the seed-head is rounded and the bristles below each flower spikelet are relatively long (15-30 mm long). 

P. purpureum is also similar to some Setaria species such as Setaria sphacelata (Queensland Department of Primary Industries and Fisheries, 2011). In Florida, P. purpureum may be confused with the larger native foxtails (Setaria spp., also called bristle grasses), but their spikelet bristles are persistent on the flowering stalks, not falling with mature spikelets. P. purpureum can be distinguished from other Pennisetum species in Florida by its long leaf blades, sparsely plumose bristles, and minute or absent first glumes (Langeland et al., 2008).

Prevention and Control

A combination of manual and chemical methods is recommended for the management of large infestations of P. purpureum. In the case of smaller infestations, plants can be cut out and all rhizomes must be removed (Weber, 2003). Larger infestations can be controlled by mowing or burning the foliage and the aboveground segments of the grass. Later any re-sprout should be sprayed with a foliar application of the herbicide 2,2 dichloropropionic acid (2,2 DPA; Weber, 2003). The herbicide glyphosate provides acceptable control in at least aquatic sites (Francis, 1992).

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Links to Websites

Contributors

03/07/13 Original text by:

Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH, Washington DC, USA

Pedro Acevedo-Rodríguez, Department of Botany-Smithsonian NMNH, Washington DC, USA

Distribution Maps