Shield Pennywort, Hydrocotyle, Whorled Pennywort, Brazilian Pennywort, Whorled Marshpennywort, Whorled Marsh Pennywort, Whorled Pennyroyal

Quick Facts

Shield Pennywort is native to the eastern states of Australia, Papua New Guinea, most of the Americas and some parts of Africa.
It is not native to Western Australia and posses a risk of becoming a weed there, similar to Hydrocotyl (Hydrocotyle ranunculoides).
Shield Pennywort is a creeping, perennial, semi-aquatic herb with creamy-white flowers.
Shield Pennywort can be controlled with herbicides.

What Does It Look Like?

What is it?

Shield Pennywort (Hydrocotyle verticillata) is a semi-aquatic, perennial herb with creeping stems which roots at the joints of its stems. The leaves are circular, 20-40 mm in diameter, with a leaf stalk up to 25 cm long, attached centrally on the under surface of the leaf. The leaf margins are crenate (with shallow rounded teeth). The inflorescence (floral structure) is simple or has two or more branches arranged in 2–7 whorls (rings).

The flowers are sessile (stalkless) and in groups of 2–5. The stalk of the peduncle (flowering head stalk) is about half as long as the leaf stalk. The petals are creamy-white and sit on top of an ovary with two lobes.

The fruit is ribbed, laterally flattened and about 2 mm long (Harden 2007b).

Flower colour

White

Growth form (weed type/habit)

Herb, Aquatic

Where it currently grows? Preferred habitat

Shield Pennywort is an aquatic herb growing in fresh water swamps, lagoons and along streams and rivers (Harden 2007b).

Are there similar species?

Shield Pennywort is easily confused with the introduced species Hydrocotyle bonariensis, but the two species may be distinguished as H. bonariensis has more complex flower heads and heart-shaped fruit with prominent veins whereas H. verticillata has round fruit with inconspicuous veins (Harden 2007a, 2007b).

Why Is It A Weed?

What are its impacts?

Shield Pennywort (Hydrocotyle verticillata) is native to Australia. It is not considered to be a weed in any Australian State except Western Australia. The Western Australian Department of Agriculture and Food has listed it as a category P1/2 weed as it is considered to be potentially invasive there, but notes that it is not known to occur in that state (Department of Agriculture and Food 2008).

Native ecosystems: Shield Pennywort has very similar characteristics to Hydrocotyl (Hydrocotyle ranunculoides) which is a serious weed in Western Australia (Randall 2008 pers. comm.). By forming extensive mats over the water, Hydrocotyl disrupts the ecology and the recreational uses of waterways. Dense floating mats of Hydrocotyl interfere with navigation, irrigation and river ecology. They can also constitute a safety hazard if humans or animals fall through a mat or are dragged under by the river current (Agriculture Protection Board of Western Australia 1993; Canning River Regional Park Management Plan 1997-2007).

How does it spread?

Shield Pennywort is dispersed by seed and stem segments which root at nodes (Harden 2007b).

What is its history in Australia?

Shield Pennywort is native to the eastern coast of Australia, and south through to Adelaide (Harden 2007b).

How To Manage It?

Best practice management

Chemical control: Some herbicides can be used whenever green leaf surface is exposed, while others should be used only while the plant is actively growing (Department of Agriculture and Food 2008). Care should be taken when applying herbicides to aquatic plants to avoid contaminating water.

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au

Does it have a biological control agent?

When does it grow? (lifecycle/growth calendar)

Shield Pennywort is a perennial that flowers from November to April (Harden 2007b).

Where Is It Found?

Which states and territories is it found?

Native to NSW, QLD, SA, VIC
Not native to WA

What areas within states and territories is it found?

The Australian native species, Shield Pennywort (Hydrocotyle verticillata), occurs along the east coast of Australia from Queensland to Victoria and in the vicinity of Adelaide in South Australia (AVH 2008). There are 2 records of the plant in the south-west of Western Australia around 1900 (State Herbarium of South Australia 2008), although it is currently reported as not being present in the state (Department of Agriculture and Food, Western Australia 2008). In some areas of Queensland it is considered to be rare (McNeill 2005).

Where does it originate?

Hydrocotyle verticillata is native to Australia and commonly known as Shield Pennywort. Shield Pennywort is widespread throughout much of the tropics and subtropics including Australia, New Guinea, South Africa, Angola, Uganda, the United States of America, Central and South America (Aluka 2008). It is used extensively in aquaria and generally known as Whorled Pennywort or Brazilian Pennywort. It is not considered to be a weed in any Australian state except Western Australia (Department of Agriculture and Food, Western Australia 2008), where it is listed due to its similarity to the serious weed Hydrocotyl (Hydrocotyle ranunculoides) (Randall 2008 pers. comm.).

For further information and assistance with identification of Shield Pennywort, contact the herbarium in your state or territory.

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

Names And Taxonomy

Main scientific name

Hydrocotyle verticillata

Other scientific names (synonyms)?

Hydrocotyle vulgaris L. (misapplied by G.Bentham, Fl. Austral. 3: 339 (1867); F.M.Bailey, Syn. Queensl. Fl. 208 (1883); F.J.H. von Mueller, Syst. Census Austral. Pl. 62 (1882); C.Moore, Census Pl. N.S.W. 29 (1884); F.J.H. von Mueller, Second Syst. Census Austral. Pl. 106 (1889), p.p.; J.H.Maiden & E.Betche, Census N.S.W. Pl. 160 (1916); A.J.Ewart, Fl. Victoria 894 (1931); J.M.Black, Fl. S. Austral. 1st edn, 3: 436 (1926); J.M.Black, Fl. S. Austral. 2nd edn, 3: 651 (1952))

Does it have other known common name(s)?

Hydrocotyle, Whorled Pennywort, Brazilian Pennywort, Whorled Marshpennywort, Whorled Marsh Pennywort, Whorled Pennyroyal

Explore in the Atlas of Living Australia

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