Weed Alert: Hygrophila
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Contacts and Further InformationIf you find this weed please help to prevent its further spread by contacting your local Council Weeds Officer or the nearest NSW Department of Primary Industries office immediately for positive identification and further assistance.
Alternatively call the NSW Weeds Hotline on
1800 680 244 or send an email to email@example.com
Hygrophila (Hygrophila costata)
Hygrophila is a highly invasive aquatic weed. It grows up to 1.5 m high in shallow water, forming mats of dense growth around the margins of freshwater lakes, rivers and watercourses where it can dominate and out-compete other vegetation. It grows all year round but most rapidly during the warmer months.
Dense infestations are likely to displace native flora and fauna by destroying their natural habitat. Hygrophila can also interfere with recreational activities such as boating and access to the water’s edge.
In New South Wales (NSW), hygrophila has become invasive in the far north coast, central coast and greater Sydney regions. Infestations are also occurring in southeast Queensland.
Hygrophila is native to the Americas from southern Mexico to Argentina, and has naturalised in many tropical and subtropical areas around the world.
Reproduction is by either seed or stem fragments. Spread occurs when seeds and plant fragments attach to animals, machinery or watercraft, or are dispersed by wind or water.
Spreading stems sprout new roots from their nodes when they come in contact with the soil, enabling a new plant to form.
Hygrophila is an erect emergent herb which grows to 1.5 m in height.
Key identification features
- Leaves are hairy, up to 18 cm long and 3 cm wide, in opposite pairs and tapering at their base. They have prominent veins and a distinct midrib.
- Upper stems are 4-angled, erect and rarely branched; lower stems are prostrate and root at nodes; the stems may have a red to purplish colour.
- Flowers have white petals and are about 10 mm long. They occur in whorls just above the junction between leaves and the stem.
- Fruit capsules are about 7 mm long, spindle-shaped and inconspicuous. Seeds are pale brown, flattened, round, about 0.3 mm wide and become sticky when wet.
Control of hygrophila is very difficult as new infestations can form from any remaining pieces of the plant. Contact your local council weeds officer for assistance if you suspect you have found hygrophila.
Hygrophila is a Class 2 Regionally Prohibited Weed in parts of NSW under the Noxious Weeds Act 1993. It must be eradicated and land must be kept free of the plant. As a notifiable weed, all outbreaks must be reported to the local council within 24 hours, and the plant is prohibited from sale in NSW.
Authors: Peter Gorham, John Hosking; Reviewers: Melissa Freeman, Birgitte Verbeek; Editors: Annie Johnson, Elissa van Oosterhout.