Weed Alert: Heteranthera

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Heteranthera (Heteranthera reniformis)

World Status | Spread | Identification | Control | Legislation

Heteranthera also known as kidneyleaf mud plantain, is a sprawling annual or perennial aquatic plant. It is able to form dense mats and colonise open shallow water, such as disturbed wetlands and flooded rice production. Such characteristics make this weed a potential threat to native vegetation and freshwater aquatic habitats.

Heteranthera will quickly colonise open sunny areas but does not grow well in shaded areas, or amongst taller growing vegetation such as sedges and tall grasses. It is most commonly found along roadside ditches, streams, ponds, drains, freshwater tidal mudflats and riverbeds.

Heteranthera was introduced to Australia as an ornamental pond plant and has been actively promoted on a number of Australian websites. In February 2006, a naturalised population was found in northern Sydney. Then in late 2007, another population was located in coastal South East Queensland. Soon after, more than 20 additional sites were found in South East Queensland.

A number of small infestations have occurred in New South Wales (NSW) in the upper Richmond catchment, and in the Bellingen, Wyong, Newcastle and Dungog local government areas. More significant infestations have occurred at Coffs Harbour and Gloucester. All current infestations are subject to active control programs.

World Status

Heteranthera has a wide natural distribution, originating from North, Central and South America.

It has naturalised in Italy, Spain and areas of the USA that are outside of its native range. Heteranthera is a weed of rice crops in a number of European countries; particularly in Italy where rice yields have been drastically reduced by the presence of this weed.

Spread

Heteranthera’s main method of dispersal is through vegetative reproduction. Any stem fragment containing one or more nodes is capable of producing a new plant. Plant fragments can be washed downstream or moved to a new location in mud stuck to animals or vehicles.

Seeds are winged and small, allowing them to be dispersed by wind and water. Seeds are capable of existing in the soil for many years.

Identification

Heteranthera is 20–50 cm tall and grows in fresh water less than 15 cm deep and on damp soil at the water’s edge. The stems can grow along the mud under the water, with leaves and stems emerging, or the whole plant can float. Roots occur at nodes along the stem.

Key identification features

• Leaves are kidney-shaped, bright green and glossy, up to 5 cm wide and arranged alternately along the stem. They are attached to a stalk 2–13 cm long and are either floating or emerging above the water.  Occasionally, a cluster of basal leaves may occur without a stalk.
• Leaves of seedlings are narrow broadening with age.
• Flowering stems are a spike 1–9 cm long containing 2–8 flowers. Each flower has six white-to-pale blue petals. Flowers open a few hours after sunrise, wilting by early afternoon. Flowering occurs summer and autumn in temperate to subtropical areas and all year in the tropics.
• Fruits are capsules 0.5–0.9 mm long and contain 8–14 winged seeds.

Control

A local council weeds officer will assist with identification, control information, removal and eradication. Heteranthera is capable of spreading from plant fragments and strict hygiene procedures are required for the control of this plant.

Legislation

Heteranthera is a Class 1 State Prohibited Weed across 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.

Acknowledgments

Reviewed by: Charlie Mifsud, Rod Ensbey; Edited by: Elissa van Oosterhout

References

• Csurhes S (2008) Kidneyleaf mudplantain Heteranthera reniformis Pest Plant Risk Assessment, Queensland Government–Department of Primary Industries and Fisheries, Brisbane
• Hosking JR, Sainty GR, Jacobs SWL & Dellow LL (in prep) The Australian WeedBOOK