Tiwi Weeds - Grasses
Gamba Grass (Andropogon gayanus)
Weed of National Significance – report to Tiwi Rangers immediately if found
NT Declaration Status: Class A
Large erect tussock grass to 4 m high.
Occurs in disturbed areas, open forests and woodlands.
Strong stems covered in soft velvety white hairs.
Leaves broad and softly hairy to 1 m, with a distinctive white midrib. Leaves stay green after native grasses have died off.
Seed heads are V-shaped and fluffy, developing above the leaves on thick stems.
Gamba Grass grows rapidly to form large tussocks that are taller and denser than native grass species and threatens ecosystems by dramatically altering fire regimes, reducing tree cover, and impacting plant and animal biodiversity. It also poses a significant risk to human life and property in areas it invades as it radically increases the likelihood of severe fire.
Mossman River Grass (Cenchrus echinatus)
NT Declaration Status: Class B
Erect annual grass to 50 cm with stems also rooting at lower nodes.
Leaves pale, flat and taper at the tips.
Seed head green to purple or brown, spike like and carries a cluster of up to 50 spiny burrs, which are easily transported by people and on the fur of animals.
Flowers from November to May.
Mossman River Grass is an aggressive competitor that colonises sandy soils, particularly along the coast, and can have a significant impact on coastal sand dune communities.
Mission Grass (Cenchrus polystachios)
NT Declaration Status: Class B
Large, tough, perennial grass, forming loose clumps to 3 m high
Occurs in open forests and woodlands, especially in disturbed areas
The leaf blades are hairy and elongated up to 45 cm long and 1.8 cm wide and can be a red purplish colour at the base.
Leaves stay green long after native grasses have died off, providing fuel for fires later in the year.
Flower heads appear in the early Dry Season (April to June) and are a dense golden spike, up to 26 cm long and 1.3-2.6 cm wide.
Perennial Mission Grass competes with native species and provides fuel for hotter fires later in the Dry Season. The fuel load from Mission Grass can be three to five times that of native species.
Guinea Grass (Megathyrsus maximus)
NT Declaration Status: No NT status, environmental weed.
Tufted perennial introduced pasture grass that may form large clumps up to 3 m high.
Leaf blades are long, narrow and taper to a fine point. They have a prominent mid-rib and are approximately 1 cm wide.
Seed heads are large (up to 40 cm long) and are well-spread, with many fine branches. Seeds are oblong in shape, often purple in colour and are easily spread on the fur of native mammals.
Guinea Grass is an aggressive weed that can outcompete native vegetation for light, water, and nutrients. It also alters fire regimes and modifies soil nutrient cycles.