This is a robust, perennial deep water grass which can grow to 3 metres with
support and 1.5 without support.
Stems are erect or ascending from a prostrate base and contain white pith. Roots
may be produced at the lower nodes.
Leaf blades are green, 10 to 45 centimetres long, up to 3 centimetres wide, strongly
clasping the stem at the base and have prominent light coloured veins and hairy
Flower heads are dense, spike-like, cylindrical, 20 to 40 centimetres long and 8
millimetres wide, sometimes branched. Main flowering occurs from April to June.
Habitat hymenachne grows in moist soil and in water up to 1.5 metres deep.
Weed characteristics it invades and chokes waterways including drains, lagoons,
creeks, rivers, wetlands and the edges of mangroves, where it can reduce oxygen
levels and turn water stagnant which affects fish populations. It interferes with
irrigation, infrastructure and wildlife habitats.
Dispersal occurs by water movement and migratory aquatic birds.
How to act
Drawing down (drying out) the area combined with controlled grazing can provide some temporary containment of spread. Foliar spraying with a suitable herbicide registered for use over water is effective for control. Follow-up monitoring and control is usually required. An integrated approach using mechanical, fire, chemical and biological control combined with pasture management is most effective.
Refer to Weed Control Methods.
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