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Kidney-leaf mud plantain (Heteranthera reniformis)

Introduced to Australia as an ornamental pond plant, kidney-leaf mud plantain is a water weed that can form dense mats in shallow water and damp soil. It is actively being controlled in NSW because it can choke waterways, displace native water plants and reduce rice yields.

Key facts

Type: Weed, aquatic.

Native to: North, Central and South America.

Established in: QLD, NSW, WA.

Identification

  • It is an annual or perennial plant that grows 20–50 cm above mud or water.
  • Stems may spread along mud, grow underwater or float, and roots form at the stem nodes.
  • Leaves are bright green, spongy and glossy, kidney-shaped and up to 5 cm wide; they are often on stalks 2–13 cm long.
  • White, mauve or pale-blue flowers have six petals, with a yellow and brownish-purple spot on one petal.
  • Flowers grow on spikes 1–9 cm long, with 2–10 flowers per spike.

Where it grows

In NSW it is found mainly in the North Coast, Hunter and Greater Sydney regions, with other records near Leeton in the Riverina and in the South East, in shallow freshwater, damp waterside soil and wetlands.

Why it matters

  • Dense mats can choke dams, drains and water supply channels, reducing water flow.
  • It can prevent native water plants from growing and reduce food for fish and other aquatic life.
  • It can significantly reduce rice yields, with reductions of up to 70% reported for water-sown rice in Europe.

How it spreads

  • Wind and water disperse its winged seeds; seeds can also travel in mud stuck to birds and vehicles.
  • Stem fragments with one or more nodes can produce new plants, and this is the main way the weed spreads.
  • Fragments can wash downstream or be carried in mud or debris stuck to animals, people or vehicles.

Control options

  • If you suspect you have found it, contact a local council weeds officer as soon as possible for identification and control advice.
  • Strict hygiene is required because stem fragments can produce new plants.
  • Avoid running boat motors or paddling through water plants, and never dump unwanted water plants.

Hygiene and washdown

  • Before leaving waterways, check and remove all plant material from boats, canoes, trailers, vehicles, machinery and fishing gear.
  • Avoid running boat motors or paddling through water plants, and never dump unwanted water plants.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Restricted matter, categories 3, 5. Do not give it away, sell or release it into the environment; do not keep it. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Regional priority in 8 of 11 regions. Regional priority weed in Central West, Greater Sydney, Hunter, Murray, North Coast, North West, Riverina, South East. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Declared pest (C1), prohibited. C1 Exclusion: to be kept out of WA, or out of the parts of WA where it is not established. Report any sighting to DPIRD. It must not be brought into WA (prohibited organism).
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Check NT list. There is no NT weed profile for it. Check the NT declared weeds list for its current status.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources