- Introduced from South and Central America as a ponded pasture, Hymenachne invades and chokes out waterways, including drains, lagoons, creeks, wetlands and the edges of mangroves, where it tends to stagnate water and reduce oxygen levels, affecting fish populations.
- Grows on moist soil and in water to 1.5 m deep.
- Growth is enhanced by nutrient enrichment and sedimentation.
- Robust, perennial deep-water grass, 1-1.5 m high.
- Stems erect or ascending from a prostrate base.
- Leaf blades green, 10-45 cm long, 3-6 cm wide, strongly clasping the stem at the base, prominent light coloured veins, hairy margins.
- Flower heads are dense, spike-like, cylindrical, 20-40 cm long and 8 mm thick, sometimes branched.