Persicaria hydropiper

{{Short description|Species of plant}} {{Speciesbox | name = Water pepper | image = Persicaria hydropiper leaves.JPG | image_caption = | status = LC | status_system = IUCN3.1 | status_ref = <ref name=IUCN>{{cite iucn |last1=Lansdown |first1=R.V. |year=2014 |title=''Persicaria hydropiper'' |volume=2014 |article-number=e.T163977A42399743 |doi=10.2305/IUCN.UK.2014-1.RLTS.T163977A42399743.en |access-date=21 February 2026}}</ref> | genus = Persicaria | species = hydropiper | authority = (L.) Delabre 1800 | synonyms_ref = <ref>[http://www.theplantlist.org/tpl1.1/record/kew-2572559 The Plant List, ''Persicaria hydropiper'' (L.) Delarbre ]</ref> | synonyms = {{collapsible list|bullets = true |title=Synonymy |''Polygonum hydropiper'' L. 1753 |''Persicaria hydropiper'' (L.) Opiz 1852 |''Persicaria hydropiper'' (L.) Spach 1841 |''Persicaria acris'' Gilib. |''Persicaria glandulosa'' Nakai & Ohki |''Persicaria urens'' Garsault |''Persicaria vernalis'' Nakai |''Peutalis hydropiper'' Raf. |''Polygonum glandulosum'' Poir. |''Polygonum gracile'' Salisb. |''Polygonum hecasanthum'' Schur |''Polygonum hidropiper'' Neck. |''Polygonum oleraceum'' Schur |''Polygonum schinzii'' J. Schust. }}}}

'''''Persicaria hydropiper''''' (syn. ''Polygonum hydropiper''), also known as '''water pepper''', '''marshpepper knotweed''', '''arse smart'''<ref name="mwarsesmart">{{Cite Merriam-Webster|arsesmart}}</ref> or '''tade''', is a plant of the family Polygonaceae. A widespread species, ''Persicaria hydropiper'' is found in Australia, New Zealand, temperate Asia, Europe and North America.<ref>[http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200006723 Flora of China, ''Polygonum hydropiper'' Linnaeus, 1753. 辣蓼 la liao ]</ref><ref>Dennis I. Morris DI (2009) Polygonaceae, version 2009:1. In MF Duretto (Ed.) Flora of Tasmania Online. 17 pp. (Tasmanian Herbarium, Tasmanian Museum & Art Gallery: Hobart). {{ISBN|978-1-921599-30-9}}.</ref><ref>[http://bonap.net/MapGallery/County/Persicaria%20hydropiper.png Biota of North America Program 2014 county distribution map]</ref><ref>[http://luirig.altervista.org/flora/taxa/index1.php?scientific-name=persicaria+hydropiper Altervista Flora Italiana, ''Persicaria hydropiper'' (L.) Spach] includes photos, drawings, European distribution map</ref> The plant grows in damp places and shallow water. Cultivated varieties are eaten in East Asia for their pungent flavor.

==Description== thumb|left|Stem of ''Persicaria hydropiper'', showing sheathed 'nodes' at base of leaves Water pepper is an annual herb with an erect stem growing to a height of {{convert|20|to|70|cm|0|abbr=on}}. The leaves are alternate and almost stalkless. The leaf blades are narrowly ovate and have entire margins fringed by very short hairs. They are tapering with a blunt apex. Each leaf base has stipules which are fused into a stem-enclosing sheath that is loose and fringed at the upper end. The inflorescence is a nodding spike. The perianth of each tiny flower consists of four or five segments, united near its green base and white or pink at the edges. There are six stamens, three fused carpels and three styles. The fruit is a dark brown oval, flattened nut.<ref name=NatureGate>{{cite web |url=http://www.luontoportti.com/suomi/en/kukkakasvit/water-pepper |title=Water pepper: ''Persicaria hydropiper'' |publisher=NatureGate |accessdate=2013-12-30}}</ref>

''P. hydropiper'' is an annual, and prefers damp environments for optimal growth; it will readily grow in riparian zones on the banks of streams and rivers, but can also grow in other areas where water collects, such as on the banks of canals, tyre and hoof tracks in woodlands, waterlogged soil, and around gates in fields. ''P. hydropiper'' is also tolerant of partial shade and base-poor soil. In the United Kingdom, where the plant is native, it can grow at any altitude between sea level and 505 metres.<ref>{{Cite web |title=Persicaria hydropiper {{!}} Online Atlas of the British and Irish Flora |url=https://plantatlas.brc.ac.uk/plant/persicaria-hydropiper |access-date=2022-05-16 |website=plantatlas.brc.ac.uk |language=en}}</ref>

==Biochemistry== Water pepper has several active ingredients. Two bicyclic sesquiterpenoids are present, polygodial (tadeonal, an unsaturated dialdehyde with a drimane backbone), and warburganal, which gives it its pungent taste.<ref>{{cite web |url=http://www.organic.lu.se/Publications/Ph.%20D.%20theses/Jonassohn.pdf |last=Jonassohn |first=M. |date=1996 |title=Sesquiterpenoid unsaturated dialdehydes - Structural properties that affect reactivity and bioactivity |access-date=2008-01-30 |archive-date=2011-10-03 |archive-url=https://web.archive.org/web/20111003033550/http://www.organic.lu.se/Publications/Ph.%20D.%20theses/Jonassohn.pdf |url-status=dead }}</ref> The plant also contains rutin, a source of the bitter taste impression.

Water pepper contains an essential oil (0.5%) which consists of monoterpenoids and sesquiterpenoids: α-pinene, β-pinene, 1,4-cineol, fenchone, α-humulene, β-caryophyllene, trans-β-bergamotene. Carboxylic acids (cinnamic, valeric and caproic acid) and their esters were present in traces. The composition depends strongly on genetic factors.

Wild water pepper produces oils that cause skin irritation.<ref>[http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242100096 Flora of North America]</ref>

== Uses == Water pepper is eaten in Japan, where it is known as ''tade'' (蓼), or more specifically, ''yanagi tade'' (柳蓼). The leaves of cultivated plants are used as a vegetable, as the wild type has a far more pungent taste. The herb is usually sold in markets as seedlings.<ref name="sanderson">{{cite book |editor1-last=Prance |editor1-first=Ghillean |editor2-last=Nesbitt |editor2-first=Mark |last1=Sanderson |first1=Helen |last2=Renfrew |first2=Jane M. |date=2005 |title=The Cultural History of Plants |publisher=Routledge |page=110 |isbn=0415927463}}</ref> Young red sprouts are known as ''beni-tade'' (紅蓼), and are used to garnish sashimi, tempura, and sushi. It is popular for summer cooking.<ref name="sanderson"/> The seeds may also be added to wasabi.

Water pepper sauce, known as ''tade-zu'' (蓼酢), is a sauce traditionally made from finely chopped water pepper leaves, soaked in vinegar, and a small amount of steamed rice. Occasionally, the juice from a squeezed kabosu is added. In Japanese cuisine it is traditionally used as a complement to grilled freshwater fish, but not saltwater fish.<ref>{{Citation |title=Citation Needed |date=2017-04-03 |work=Retcon Game |url=https://doi.org/10.14325/mississippi/9781496811325.003.0047 |access-date=2025-10-06 |publisher=University Press of Mississippi |doi=10.14325/mississippi/9781496811325.003.0047 |isbn=978-1-4968-1132-5|url-access=subscription }}</ref>

In China, water pepper is known as ''là liǎo'' (辣蓼) or ''shuǐ liǎo'' (水蓼), and used in traditional Chinese medicine.

In Indian traditional medicine, leaves of ''P. hydropiper'' are used against intestinal helminth infections. A study has proved that ''P. hydropiper'' leaves possess noteworthy anthelmintic efficacy and justify their use in traditional medicine against intestinal worms. DOI: 10.1007/s12639-022-01559-2

In Europe, water pepper was once cultivated and eaten during war time as a substitute for pepper.<ref name="sanderson"/>

The plant contains many acids, including formic acid, which makes it unpalatable to livestock.<ref>[http://www.illinoiswildflowers.info/weeds/plants/waterpepper.htm Illinois Wildflowers]</ref> Though mammals do not eat wild water pepper, some insects do, giving rise to the Japanese saying "''Tade kuu mushi mo sukizuki''" (蓼食う虫も好き好き "Some insects eat water pepper and like it"), which may be translated as "There is no accounting for taste" or "Each to his own."

== Gallery == <gallery> Polygonum hydropiper1.jpg Persicaria hydropiper.JPG Polygonum hydropiper3.jpg Polygonum hydropiper2.jpg Polygonum hydropiper — Flora Batava — Volume v6.jpg|Illustration from Jan Kops' ''Flora Batava'' (1832) Polygonum hydropiper (1832).jpg|Illustration from ''La flore et la pomone françaises'' (1832) 356 Polygonum tomentosum, Polygonum hydropiper.jpg|Illustration from ''Bilder ur Nordens Flora'' (1917–1926) </gallery>

== See also == * Rui-be

==References== {{Reflist}}

==External links== {{Commons}} * [http://ucjeps.berkeley.edu/cgi-bin/get_JM_treatment.pl?5936,6248,6269 Jepson Manual Treatment, University of California] * [http://www.anbg.gov.au/cgi-bin/apni?taxon_id=287693 Australian Plant Name Index (APNI)] {{Webarchive|url=https://web.archive.org/web/20110602215505/http://www.anbg.gov.au/cgi-bin/apni?taxon_id=287693 |date=2011-06-02 }}

hydropiper Category:Spices Category:Flora of Europe Category:Flora of Australia Category:Flora of temperate Asia Category:Flora of tropical Asia Category:Flora of Northern America Category:Plants described in 1753 Category:Botanical taxa named by Carl Linnaeus