Hydrocotyle ranunculoides

Water pennywort is an aquatic plant, native to the Americas. Due to its popularity as a pond plant, and subsequent escape into rivers, it has established as an invasive alien species in parts of Europe, Australia, Africa and Japan.{{Cite web|last=|first=|date=|title=Hydrocotyle ranunculoides (floating pennywort)|url=https://www.cabi.org/isc/datasheet/28068|archive-url=|archive-date=|access-date=3 February 2021|website=Invasive Species Compendium}}{{Cite web|url=http://www.environment-agency.gov.uk/research/library/publications/103309.aspx|title=Invasive non-native species - indicator two|website=Environment Agency|archive-url=http://webarchive.nationalarchives.gov.uk/20100513120702/http://www.environment-agency.gov.uk/research/library/publications/103309.aspx|archive-date=13 May 2010|url-status=|access-date=28 August 2017}}{{Cite news|url=http://www.theecologist.org/News/news_analysis/271174/aquatic_invaders_threat_to_biodiversity.html|title=Aquatic invaders threat to biodiversity|work=The Ecologist|access-date=2017-08-28}} It was one of five aquatic plants which were banned from sale in the UK from April 2014, and was the first prohibition of its kind there.{{Cite news|url=https://www.bbc.co.uk/news/science-environment-21232108|title=UK bans sale of five invasive non-native aquatic plants|last=Kinver|first=Mark|date=2013-01-29|work=BBC News|access-date=2017-08-28|language=en-GB}} On the other hand, it is in decline in parts of its range in the United States.{{Cite web|last=|first=|date=|title=Plants Profile for Hydrocotyle ranunculoides (floating marshpennywort)|url=http://plants.usda.gov/java/profile?symbol=HYRA|archive-url=|archive-date=|access-date=2021-02-03|website=USDA, NRCS. 2021. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.}}

In Europe, floating pennywort is included since 2016 in the list of Invasive Alien Species of Union concern (the Union list).{{Cite web|title=List of Invasive Alien Species of Union concern - Environment - European Commission|url=https://ec.europa.eu/environment/nature/invasivealien/list/index_en.htm|access-date=2021-07-27|website=ec.europa.eu}} This implies that this species cannot be imported, cultivated, transported, commercialized, planted, or intentionally released into the environment in the whole of the European Union.{{Cite web|title=REGULATION (EU) No 1143/2014 of the European parliament and of the council of 22 October 2014 on the prevention and management of the introduction and spread of invasive alien species|url=https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32014R1143&from=EN}}

Water pennywort has stems that spread horizontally and can float on water.{{cite web|last=John|first=Hilty|date=|title=Water Pennywort|url=http://www.illinoiswildflowers.info/wetland/plants/wt_pennywort.htm|archive-url=|archive-date=|accessdate=16 December 2012|website=Illinois Wildflowers}} Leaves grow on petioles up to 35 cm long, and are round to kidney-shaped, with 3–7 lobes and crenate to entire margins.{{cite web|title=H. ranunculoides|url=http://ucjeps.berkeley.edu/cgi-bin/get_JM_treatment.pl?329,413,415|work=Jepson Manual|publisher=University of California|accessdate=16 December 2012}} Flowers are small, pale greenish white to pale yellow, and come in umbels of 5–13. Fruits are small achenes that can float, helping the seeds to disperse.

The South American weevil Listronotus elongatus lays eggs on and eats the floating pennywort, and larvae also eat into the stems, reducing the pennywort's ability to grow. The weevil has been introduced for biocontrol of the floating pennywort into waterways in Britain, following extensive research to establish that the weevil is not a threat in itself.{{Cite news |title=South American weevils released in UK waterways to tackle invasive weed |last=Horton |first=Helena |newspaper=The Guardian |date=17 May 2022 |url= https://www.theguardian.com/environment/2022/may/17/south-american-weevils-released-uk-waterways-tackle-invasive-weed-floating-pennywort}}

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ranunculoides

Category:Flora of Northern America

Category:Flora of Southern America

Category:Taxa named by Carl Linnaeus

Category:Flora without expected TNC conservation status

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