Hydrocotyl (Hydrocotyle ranunculoides)

PROHIBITED MATTER: If you see this plant report it to the NSW Invasive Plants & Animals Enquiry Line 1800 680 244
Also known as: water pennywort

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Impact

Hydrocotyl, also known as water pennywort, is an aquatic perennial plant that can rapidly form a dense mat in stationary or slow-flowing freshwater such as rivers, wetlands, lakes and dams.

The high growth rates and dense mats formed by hydrocotyl allow it to quickly replace native vegetation and reduce habitat for native fauna.

Distribution

Hydrocotyl is native to the Americas, tropical Africa and Asia.

It has become a serious weed in Belgium, the Netherlands and England, Wales and Ireland following its introduction from the nursery trade in the 1980s, where it is believed it was wrongly labelled as the native species Hydrocotyle vulgaris.

Hydrocotyl has naturalised in South Africa and has spread into a number of other European countries including France, Germany and Italy.

Originally introduced to Australia as an aquarium and ornamental pond plant, the first infestation was recorded in 1983 near Perth, Western Australia. In 1992 a more substantial infestation of hydrocotyl was discovered, which covered one third of the water surface along a 7 km stretch of the Canning River in Western Australia.

Hydrocotyl is currently found in coastal freshwater streams and water storages near Perth. It is potentially a serious weed of freshwater wetlands and other nutrient enriched watercourses throughout most of coastal Australia. No infestations have been recorded in New South Wales.

Description

Hydrocotyl is a perennial hairless plant with long stolons. Roots are produced at each node and leaves float or emerge up to 40 cm above the water surface. The tangled mass of roots and leaf stems can sink up to 50 cm into the water.

Key identification features

  • Leaves occur alternately along the stolons, are circular to kidney-shaped, up to 10 cm wide and contain 3–7 lobes with shallow-toothed edges. Each leaf stalk emerges from nodes along the stolon, is 2–25 cm long and attaches to the bottom of the leaf, close to the centre.
  • Tiny greenish, yellowish or white five-petalled flowers (2–3 mm in diameter) occur below the leaf canopy in clusters of 5–10. Flower stalks are slender, about 2 cm long and arise from the nodes. Flowering occurs from spring to autumn.
  • Fruit is almost circular, 1–3 mm in diameter and splits into segments.

Acknowledgements

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

References

CABI Invasive Species Compendium website—www.cabi.org/isc

Hosking JR, Sainty GR, Jacobs SWL & Dellow LL (in prep) The Australian WeedBOOK

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Control

Hydrocotyl is a highly invasive plant of waterways. If you suspect you have found hydrocotyl you should contact your local council weeds officer who will assist with identification, removal and eradication.

Herbicide options

Contact your local council weeds officer for control advice for Hydrocotyl (Hydrocotyle ranunculoides).

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
All of NSW Prohibited Matter
A person who deals with prohibited matter or a carrier of prohibited matter is guilty of an offence. A person who becomes aware of or suspects the presence of prohibited matter must immediately notify the Department of Primary Industries

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For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW Invasive Plants and Animals Enquiry Line on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2017