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Giant Parramatta Grass

GPG closeup

GPG head

GPG plant

GPG, long lower branches

P'matta grass plant

P'matta grass head

Sporobolus elongatus (L) & creber (R)

 


Family: Poaceae (grasses)

Status: Giant Parramatta grass (Sporobolus fertilis) is declared noxious in class 3 in Bega Valley, Eurobodalla, Shoalhaven and Illawarra LCAs.

Description:
Giant Parramatta grass is a larger version of the very common (and not listed as noxious) weed Parramatta grass (Sporobolus africanus, or S. indicus var capensis as it was previously known). Giant Parramatta grass can reach 1.6m high, with a seed head up to 45cm long. The lower branches of giant Parramatta grass are much longer (8-11cm) than those of Parramatta grass and may hang away from the stem at maturity, but the upper part of the seed head is compact and linear, as for Parramatta grass.  The first 4 photos are Giant Parramatta grass, followed by 2 of Parramatta grass.

Parramatta grass is a tough wiry stemmed tussock, usually under 45cm high, with blue-green leaves up to 5mm wide, held either erect or spreading. Leaves are folded or flat and smooth to the touch. Flowering stems are erect with a seed head to 18cm long. The branches of the seed head are held very close to the stem, so that the whole head appears to be a single spike. If the head is bent over, to force the lower branches away from the main stem, they will be seen to be only 2.5cm long or less (compared with 8-11cm in giant Parramatta grass). The seeds are a leaden grey colour, and without awns (a long thread-like structure sometimes found on grass seeds). They are often infected with smut, a fungus, making the seed head black and lumpy.


Preferred habitat and impacts:
Parramatta grass favours sites with compacted soil, such as road verges and tracks, but it will also invade pasture and sandy coastal sites. It has very low feed value, and being very tough, can loosen the teeth of stock feeding on it.
Giant Parramatta grass behaves similarly. It is a common pasture weed on the NSW north coast, where it is particularly invasive in wet areas, but it is not yet well established on the south coast.

Dispersal:
The seed is spread in soil on machinery and vehicles, and although it has no awn or hairs, it becomes sticky when wet, and can adhere to animals and clothing.

Look-alikes:
Two native rat's tail grasses (Sporobolus elongatus, S. creber) are also common on the south coast. They have more interrupted seed heads than Parramatta grass and giant Parramatta grass, with the stem visible between the branches, at least in the lower part of the head. The length of the lower branches in these two species is only 5cm or less. Distinguishing between native and introduced Sporobolus can be difficult and expert assistance may be needed. The final photo shows Sporobolus elongatus on the left and Sporobolus creber on the right.

Control:
Parramatta grass is so widespread that attempts to control it are probably pointless, except in very weed-free situations, to which it may gain access along tracks. Giant Parramatta grass has arrived more recently, and any suspected infestations should be controlled immediately. Individual plants can be dug out, and the seed burnt or deeply buried. Grass-specific herbicides are preferable if spraying.