Guinea grass

Megathyrsus maximus var. maximus
Grass
Basal
Simple
Green
Green

A large, clumping, long-lived grass growing up to 3 m tall. Its long and narrow leaves are very large (up to 100 cm long and 3.5 cm wide)its large and much-branched seed-heads bear large numbers of small flower spikelets. The lowermost branches of its seed-heads are arranged in a cluster. Its hairless flower spikelets are green or purplish in colour and are shed from the seed-head entire when mature.

Common names 
Also known as: Guinea grass, green panic, purple top buffalo grass, colonial grass,
Family 
Poaceae
Deciduous 
No
Flowering time 
Spring-Autumn
Native/Exotic 
Exotic
Origin 
Native to Africa.
Notifiable 
No
Council declaration 
Class R – Reduce populations
Known distribution 

Widely naturalised in northern and eastern Australia (i.e. in northern and eastern Queensland, in eastern New South Wales, in the coastal districts of northern Western Australia and in the northern parts of the Northern Territory). Also recorded in south-western Western Australia, the southern parts of the Northern Territory, and on Norfolk Island.

Habitat 

A very common and widespread weed of crops, orchards, vineyards, disturbed sites, roadsides, railways, footpaths, parks and gardens, bushland and riparian vegetation in the tropical, sub-tropical, warmer temperate and semi-arid regions of Australia.

Habit 

A long-lived (i.e. perennial) grass with short underground stems (i.e. rhizomes) forming tufted clumps and aboveground stems that are usually upright (i.e. erect) in nature. Guinea grass (Panicum maximum var. maximum ) grows up to 3 m tall, but is usually about 2 m in height.

Impact and control methods 

Guinea grass (Megathyrsus maximus var. maximus) is regarded as an environmental weed in Queensland, the Northern Territory and north-eastern New South Wales.

Stem and leaves 

The stems may be branched and vary from being hairless (i.e. glabrous) to quite hairy (i.e. pilose). The leaves consist of a sheath, which encloses the stem, and a spreading leaf blade. These long and narrow leaves are very large (15-100 cm long and 5-35 mm wide) with entire margins and pointed tips (i.e. acuminate apices). Like the stems, they can vary from being hairless (i.e. glabrous) to being quite hairy (i.e. pilose), but they are most commonly sparsely hairy (i.e. puberulent). The leaf blades are usually held flat and their margins are rough to touch (i.e. scabrous). Where the leaf sheath meets the leaf blade there is a small membranous structure topped with hairs (i.e. the ligule is a ciliate membrane).

Flowers and fruits 

The seed-heads (i.e. inflorescences) are loosely branched (i.e. open panicles) and 12-60 cm long. Their lowest branches are arranged in a cluster (i.e. whorl), while the branches further up the seed-head are variously arranged. The flower spikelets are small (3-4.5 mm long) and oval (i.e. elliptic) or oblong in shape. They are generally green in colour, but occasionally may be purplish or reddish in colour. These flower spikelets are hairless and have only one fertile floret. They are shed from the seed-head entire when mature.

Reproduction and dispersal 

This species reproduces mainly by seed, which are dispersed by animals, wind, water, vehicles, machinery. Seeds may also be spread in contaminated soil and agricultural produce (e.g. fodder or grain).

Similar species 

Guinea grass (Megathyrsus maximus var. maximus) and green panic (Megathyrsus maximus var. pubiglumis) can be distinguished from each other by the following differences: Guinea grass (Megathyrsus maximus var. maximus) is a large and robust plant (1.8-3 m tall) with very large leaves and seed-heads. Its leaves are usually dark green in colour and its flower spikelets are hairless.green panic (Megathyrsus maximus var. pubiglumis) is a moderately-sized plant (usually about 1.5 m tall) with large leaves and seed-heads. Its leaves are usually paler green in colour and its flower spikelets are usually finely hairy.