pronounced: KENCK-russ eck-in-AH-tuss
Cenchrus is from the Greek κεγχρος (kengchros), millet; echinatus is from εχινος (echinos), the sea-urchin, the hedgehog – prickly. The Mossman River runs through the spectacular Mossman Gorge near Port Douglas, Far North Queensland.
Mossman River grass originates in North and South America, but is now spread over much of the tropical and sub-tropical world. It is an annual grass with either prostrate or erect stems forming loose tufts. The seedlings are erect, robust, hairless, and with bright mid-green leaves. The leaf-sheaths are purplish red, especially in the older seedlings. Mature plants form prostrate or ascending tufts with stout stems, up to 90 cm tall, but mostly to 60 cm. The leaves are flat and rather stiff, tapering towards the tip; they are 5 – 25 cm long by 3 – 12 mm wide. The ligule (where the leaf blade becomes the leaf shaft to wrap around the stem) is a ring of short hairs with a few scattered hairs on the leaf margin at the leaf base. The joints along the stems are hairless.
Seed heads, borne on several stems per plant, are spike-like clusters of anything up to 50 burrs. Each burr, 4–10 mm across, is a pale green to purplish ball of stout, broad, spiny bristles that are joined together at the base. The burrs fall off readily when ripe and cling tightly to clothing, animal hides and human skin. They can also penetrate bare human feet. The plant is spread by the seeds in the burrs, either by attachment to animals, humans and the tyres of vehicles, or by floating and moving by water. In sheep country, burrs reduce the value of the wool, and make shearing hazardous. Spines from the burrs also penetrate the hides, lowering their value.
This species has infested largish areas of Australia, and has the potential to go much further. In Queensland, there is a coastal area of infestation from here to Cairns, not stretching too far inland. There is a large area from about Rockhampton on the coast, reaching inland to about Barcaldine. There is another smaller area near Mount Isa, one round Winton, and another in the northern Channel Country. There are a few isolated areas in NSW, and the largest infected area of all is in central Australia, mostly in the Northern Territory but also stretching into Western Australia and South Australia. The other main problem area in the Northern Territory is in Arnhem Land, mostly in the north and west. This also stretches into Western Australia to the Wyndham area. Many parts of the Kimberleys are also heavily infested. Mossman River Grass has the potential to expanded its territory to cover the whole of the Australian continent except for the southern tip of Western Australia, South Australia from about Adelaide south, and most of Victoria.
Young plants are moderately palatable to grazing animals, and farmers often try to graze the grass heavily before the seed heads are able to form. The plant does, however, contain oxalates, and the eating of large amounts of these plants over a long period can cause chronic kidney disease in sheep, cattle and donkeys, resulting in muscle tremors, staggering gait, collapse and death.
