pg . 76
NQ DRY TROPICS WEED FREE
OLIVE HYMENACHNE
Hymenachne amplexicaulis
OLIVE HYMENACHNE
WATER WEEDS
DESCRIPTION
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 margins .
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 .
BIOSECURITY MATTER
Restricted . This species is Category 3 Restricted matter under Queensland Legislation .
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 .