Mossman river grass or Mossman burr (Cenchrus echinatusis) is an invasive plant native to Central America and southern North America. It prefers sandy soils including at the beach, footpaths, roadsides, lawns, parks and disturbed areas – so K’gari provides some perfect habitat.
The plant is an annual grass with prostate or erect stems forming loose tufts. Seedlings are erect, robust, hairless and have bright mid-green leaves. The leaf sheaths are purplish-red, especially in older seedlings.
Mature plants form prostrate or ascending tufts with stout stems up to 90 cm, but mostly up to 60 cm. The leaves are flat and somewhat stiff, tapering towards the tip. They are 5−25 cm long and 3−12 mm wide. The ligule (where the leaf blade becomes the leaf shaft to wrap around the stem) is a rim of short hairs, with a few scattered hairs on the leaf margin at the leaf base. The joints along the stems are hairless.
It flowers mostly during summer and autumn with seed heads, borne on several stems per plant, are spike-like clusters of 12–14 burrs. Each burr (0.5–1 cm across) is a ball of stout, broad, spiny bristles 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 feet, making it unpopular with tourists.
Mossman river grass mainly spreads by burr seeds and by burrs attached to animals, clothing and bags, machinery and vehicles, fodder, and soil.
The most effective control method is to destroy young plants before they set seed. This can be done by hand-pulling, burning off with heat using steam jets, or spraying with herbicide.
Please make sure you check your boots/clothing carefully for these burrs before moving around the island and dispose of any seeds/burrs carefully to prevent spread.