Elephant grass

Pennisetum purpureum
Grass
Alternate
Simple
Yellow
Green

A very robust grass forming large, bamboo-like, clumps (often 2-4 m tall). The leaf sheaths are hairless to stiffly hairy and there is a dense fringe of hairs where they meet the leaf blades. The large leaf blades (20-120 cm long and 1-5 cm wide) have a prominent whitish central vein the seed-head is spike-like (8-30 cm long and 1.5-3 cm wide) and very bristly the flower spikelets are surrounded by numerous bristles, one of which is larger than the others (i.e. 2-4 cm long).

Common names 
Also known as: Elephant grass, cane grass, merker grass, Napier grass, Uganda grass,
Family 
Poaceae
Deciduous 
No
Flowering time 
Year Round
Native/Exotic 
Exotic
Origin 
Native to tropical sub-Saharan Africa.
Notifiable 
No
Council declaration 
Class R – Reduce populations
Known distribution 

This species is widely naturalised in the coastal districts of northern and eastern Australia. It is most common in coastal Queensland and north-eastern New South Wales. Also present in the coastal districts of south-western and northern Western Australia, in the northern parts of the Northern Territory and on Norfolk Island. Also naturalised tropical Asia (e.g. China, the Philippines, Cambodia, Indonesia, Malaysia, Thailand and Papua New Guinea), southern USA (i.e. California, Texas and Florida), Mexico, Central America (e.g. El Salvador and Honduras), South America (e.g. Colombia and Peru), the Caribbean, and in Oceania (i.e. New Zealand, the Cook Islands, Micronesia, French Polynesia, Fiji, Guam, Kiribati, New Caledonia, Hawaii, Niue, Palau, the Marshall Islands and the Galapagos Islands).

Habitat 

A weed of waterways, wetlands, floodplains, open woodlands, forest margins and clearings, pastures, plantation crops, roadsides, disturbed sites and waste areas. It prefers wetter sites in tropical, sub-tropical and warmer temperate regions.

Habit 

A robust long-lived (i.e. perennial) grass forming large, bamboo-like, clumps. Its flowering stems (i.e. culms) often grow 2-4 m tall and may occasionally reach up to 7.5 m in height.

Impact and control methods 

Elephant grass (Pennisetum purpureum) is regarded as an environmental weed in Queensland, Western Australia and north-eastern New South Wales. It is also seen as a potential environmental weed or "sleeper weed" in other parts of Australia.

Stem and leaves 

The flowering stems (i.e. culms) are upright (i.e. erect), at least initially, and relatively robust (up to 3 cm thick). They are branched, particularly towards the top, and are somewhat hairy (i.e. distally pubescent). Older stems often produce roots (i.e. adventitious roots) from their lowermost joints (i.e. nodes), and sometimes these long stems fall over and produce similar roots where they come into contact with the ground. The alternately arranged leaves consist of a leaf sheath, that partially encloses the stem, and a spreading leaf blade. The leaf sheaths are hairless (i.e. glabrous) to stiffly hairy (i.e. hirsute) and are often particularly hairy (i.e. bearded) near where they join to the stem. The narrow (i.e. linear) leaf blades (20-120 cm long and 1-5 cm wide) are generally much less hairy (i.e. glabrous or sparsely pubescent on their undersides). They have a prominent whitish coloured central vein (i.e. midrib), a pointed tip (i.e. acuminate apex), and rough (i.e. scabrous) margins. Where the leaf sheath meets the leaf blade there is a dense fringe of hairs (i.e. a ciliated ligule) 1.5-5 mm long.

Flowers and fruits 

The elongated seed-head (8-30 cm long and 1.5-3 cm wide) is spike-like (i.e. a spiciform panicle) and greenish, yellowish or slightly purplish in colour. It is very bristly and is actually made up of a hairy main stalk (i.e. rachis) with numerous very short branches. Each of these very short branches has a few (1-5) flower spikelets, only one of which produces a seed (i.e. is fertile). These flower spikelets (4.5-7 mm long) are surrounded by numerous bristles (8-16 mm long) in several rows (i.e. an involucre), the outer ones being shorter than the inner ones. One of the bristles is significantly larger than the others (i.e. 2-4 cm long). Each of the flower spikelets have three yellow stamens and a feathery two-branched stigma that is purplish in colour. When the 'seed' (i.e. grain or caryopsis) is mature, the entire flower spikelet (including the bristles and any other sterile flower spikelets) turns brownish in colour and falls from the seed-head as a whole. The oval (i.e. ellipsoid) or egg-shaped (i.e. ovoid) 'seed' (1.8-2.2 mm long) remains concealed inside the remains of the fertile flower spikelet.

Reproduction and dispersal 

This species reproduces mainly by seed, but can also spread vegetatively via branches (i.e. tillers) and stem fragments. The seeds are dispersed by the wind and can also become attached to animals and vehicles. They may also be spread as a contaminant of agricultural produce (i.e. fodder and seeds).

Similar species 

Elephant grass (Pennisetum purpureum) is similar to mission grass (Pennisetum polystachion), African feather grass (Pennisetum macrourum), Deenanth grass (Pennisetum pedicellatum) and swamp foxtail (Pennisetum alopecuroides). It can usually be distinguished from these species by its sheer size, but can also be separated by the following differences: elephant grass (Pennisetum purpureum) is a very large and robust long-lived (i.e. 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 (i.e. terete) and the bristles below each flower spikelet are relatively long (8-40 mm).mission grass (Pennisetum polystachion) is a large long-lived (i.e. perennial) grass (usually 2-3 m tall) with yellowish or brownish coloured seed-heads. The main stem (i.e. rachis) of the seed-head is angular and the bristles below each flower spikelet are relatively long (4-25 mm long).African feather grass (Pennisetum macrourum) is a large long-lived (i.e. perennial) grass (usually 1-2 m tall) with greenish or yellowish coloured seed-heads. The main stem (i.e. rachis) of the seed-head is rounded (i.e. terete) and the bristles below each flower spikelet are relatively short (mostly less than 10 mm long).Deenanth grass (Pennisetum pedicellatum) is a moderately-sized short-lived (i.e. annual or perennial) grass (usually 30-150 cm tall) with pale purplish coloured seed-heads. The main stem (i.e. rachis) of the seed-head is angular and the bristles below each flower spikelet are relatively long (6-24 mm long).swamp foxtail (Pennisetum alopecuroides) is a moderately-sized long-lived (i.e. perennial) grass (usually 60-100 cm tall) with greenish 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 (15-30 mm long). Elephant grass (Pennisetum purpureum) is also similar to some of the pigeon grasses (Setaria spp.), including South African pigeon grass (Setaria sphacelata). However, the 'seeds' are shed without the bristles in these species (i.e. the bristles remain on the seed-head).