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{{Short description|Species of herbaceous perennial plant with fleshy, sour edible stalks  }}
{{About||other uses|Rhubarb (disambiguation)|the cartoon|Roobarb}}
{{Use dmy dates|date=June 2021}}
{{Use British English|date=April 2018}}
{{Speciesbox
| name = Rhubarb (culinary hybrid)
| image = Rheum rhabarbarum.2006-04-27.uellue.jpg
| genus = Rheum
| species = × hybridum
| authority = [[Johan Andreas Murray|Murray]]<ref name=POWO_696744-1>{{cite web |title=''Rheum'' × ''hybridum'' Murray |work=Plants of the World Online |publisher=Royal Botanic Gardens, Kew|url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:696744-1 |access-date=10 March 2019 }}</ref>
}}

'''Rhubarb''' is the fleshy, edible stalks ([[petiole (botany)|petioles]]) of species and hybrids (culinary rhubarb) of ''[[Rheum (plant)|Rheum]]'' in the family [[Polygonaceae]], which are cooked and used for food.<ref name="foust">{{Cite journal|last1=Foust|first1=Clifford M.|last2=Marshall|first2=Dale E.|date=1 November 1991|title=Culinary Rhubarb Production in North America: History and Recent Statistics|url=https://journals.ashs.org/hortsci/view/journals/hortsci/26/11/article-p1360.xml|journal=HortScience|volume=26|issue=11|pages=1360–1363|doi=10.21273/hortsci.26.11.1360|issn=0018-5345|doi-access=free|url-access=subscription}}</ref> The plant is a herbaceous [[perennial plant|perennial]] that grows from short, thick [[rhizome]]s. Historically, different plants have been called "rhubarb" in English. The large, triangular [[leaf|leaves]] contain high levels of [[oxalic acid]] and [[anthrone]] [[glycoside]]s, making them inedible. The small [[flower]]s are grouped in large compound leafy greenish-white to rose-red [[inflorescence]]s.

The precise origin of culinary rhubarb is unknown. The species ''[[Rheum rhabarbarum]]'' (syn. ''R.&nbsp;undulatum'') and ''[[Rheum rhaponticum|R.&nbsp;rhaponticum]]'' were grown in Europe before the 18th century and used for medicinal purposes. By the early 18th century, these two species and a possible [[Hybrid (biology)|hybrid]] of unknown origin, ''R.''&nbsp;×&nbsp;''hybridum'', were grown as vegetable crops in England and Scandinavia. They readily hybridize, and '''culinary rhubarb''' was developed by selecting open-pollinated seed, so its precise origin is almost impossible to determine.<ref name=TanhSuojHart19>{{Cite journal |last1=Tanhuanpää |first1=Pirjo |last2=Suojala-Ahlfors |first2=Terhi |last3=Hartikainen |first3=Merja |date=2019 |title=Genetic diversity of Finnish home garden rhubarbs (''Rheum'' spp.) assessed by simple sequence repeat markers |journal=Genetic Resources and Crop Evolution |volume=66 |issue=1 |pages=17–25 |doi=10.1007/s10722-018-0692-8 |bibcode=2019GRCEv..66...17T |s2cid=52821042 |name-list-style=amp }}</ref> In appearance, samples of culinary rhubarb vary on a continuum between ''R.&nbsp;rhaponticum'' and ''R.&nbsp;rhabarbarum''. However, modern rhubarb cultivars are [[tetraploid]]s with 2''n'' = 44, in contrast to 2''n'' = 22 for the wild species.<ref name=LibeEngl89>{{Cite journal |last1=Libert |first1=Bo |last2=Englund |first2=Roger |date=1989 |title=Present Distribution and Ecology of ''Rheum rhaponticum'' (Polygonaceae) |journal=Willdenowia |volume=19 |issue=1 |pages=91–98 |jstor=3996925 |name-list-style=amp }}</ref>

Rhubarb is a [[vegetable]] but is often put to the same culinary uses as [[fruit]]s.<ref>{{Cite book|last=Hood|first=Karen Jean Matsko|url=https://books.google.com/books?id=ftMSBQAAQBAJ&pg=PA20|title=Rhubarb Delights Cookbook: A Collection of Rhubarb Recipes|date=2014-01-01|publisher=Whispering Pine Press International
|place= Spokane Valley
| pages= 20, 22
|isbn=978-1-930948-00-6|language=en}}</ref> The leaf stalks can be used raw while they have a crisp texture, but are most commonly cooked with sugar and used in [[pie]]s, [[crumble]]s, and other [[dessert]]s. They have a strong, [[Taste#Sourness|tart taste]]. Many [[cultivar]]s have been developed for human consumption, most of which are recognised as ''Rheum'' × ''hybridum'' by the [[Royal Horticultural Society]].<ref>{{cite web 
| url = https://www.rhs.org.uk/Plants/Search-Results?form-mode=true&context=b%3D10%26hf%3D10%26l%3Den%26q%3Drheum%26s%3Ddesc%2528plant_merged%2529%26sl%3DplantForm&query=rhubarb
| title = RHS Plantfinder – Rhubarb | access-date = 23 September 2018}}</ref>

== Etymology ==

The word ''rhubarb'' is likely to have derived in the 14th century from the [[Old French]] {{lang|fr|rubarbe}}, which came from the Latin {{lang|la|rheubarbarum}} and [[Ancient Greek|Greek]] {{transliteration|grc|rha barbaron}}, meaning "foreign rhubarb".<ref>{{Cite web|title=Rhubarb|publisher= Online Etymology Dictionary, Douglas Harper Inc.|url=https://www.etymonline.com/word/rhubarb|date=2020|access-date=3 June 2020}}</ref> The Greek physician [[Pedanius Dioscorides|Dioscorides]] used the Greek word {{lang|grc|ῥᾶ}} ({{transliteration|grc|rha}}), whereas [[Galen]] later used {{lang|grc|ῥῆον}} ({{transliteration|grc|rhēon}}), Latin {{lang|la|rheum}}. These in turn derive from a [[Persian language|Persian]] name for species of [[Rheum (plant)|''Rheum'']].<ref name=Gilb55>{{Citation |mode=cs1 |last1=Gilbert-Carter |first1=H. |date=1955 |title=Glossary of the British Flora |edition=2nd |publisher=Cambridge University Press |page=69}}</ref> The specific epithet ''rhaponticum'', applying to one of the presumed parents of the cultivated plant, means "rha from the [[Pontus (region)|region of the Black Sea]]"<ref name=Gilb55/> or the river [[Volga]], ''rha'' being its ancient name.<ref>{{cite book |last=Theroux |first=Alexander |date=2017 |title=Einstein's Beets |url= |location= |publisher=Fantagraphics Books, Seattle Washington |page= 47|isbn=978-1-60699-976-9}}</ref>

==Cultivation==
[[File:Rheum rhabarbarum (Rabarber) Frambozenrood bloeiwijze.jpg|thumb|upright|Young rhubarb flowers]]
Rhubarb is grown widely, and with [[greenhouse]] production it is available throughout much of the year. It needs rainfall and an annual cold period of up to 7–9 weeks at 3&nbsp;°C (37&nbsp;°F), known as 'cold units', to grow well. The plant develops a substantial underground storage organ (rhubarb crowns) and this can be used for early production by transferring field-grown crowns to warm conditions.<ref name="RHS - rhubarb-growing">{{cite web |title=Rhubarb |url=https://www.rhs.org.uk/vegetables/rhubarb/grow-your-own |website=Royal Horticultural Society |access-date=23 January 2022}}</ref> Rhubarb grown in hothouses (heated greenhouses) is called "hothouse rhubarb", and is typically made available at consumer markets in early spring, before outdoor cultivated rhubarb is available. Hothouse rhubarb is usually brighter red, tenderer and sweeter-tasting than outdoor rhubarb.<ref name="Rombauer, Irma S. Page 142">Rombauer, Irma S. (1975) ''Joy of Cooking''. Indianapolis/New York: Bobbs-Merrill Co., Inc. p. 142. {{ISBN|978-0-672-51831-7}}</ref> After forcing for commercial production, the crowns are usually discarded.<ref name="RHS - rhubarb-growing" /> In [[Temperateness|temperate climate]]s, rhubarb is one of the first food plants [[harvest]]ed, usually in mid- to late spring (April or May in the [[Northern Hemisphere]], October or November in the [[Southern Hemisphere]]), and the season for field-grown plants lasts until the end of summer.

In the United Kingdom, the first rhubarb of the year is harvested by candlelight in [[Rhubarb forcer|forcing sheds]] where all other light is excluded, a practice that produces a sweeter, more tender stalk.<ref name=b1>McGee, Harold (2004). ''[[On Food and Cooking]]''.  New York, NY: Scribner.  p 367. {{ISBN|978-0-684-80001-1}}</ref> These sheds are dotted around the "[[Rhubarb Triangle]]" in [[Yorkshire]] between [[Wakefield]], [[Leeds]], and [[Morley, West Yorkshire|Morley]].<ref name="wgur">{{cite web|author=Wakefield Metropolitan District Council|url=http://www.wakefield.gov.uk/CultureAndLeisure/HistoricWakefield/Rhubarb/default.htm|title=Rhubarb|access-date=12 March 2006|archive-url=https://web.archive.org/web/20080930091049/http://www.wakefield.gov.uk/CultureAndLeisure/HistoricWakefield/Rhubarb/default.htm|archive-date=30 September 2008}}</ref>

In the United States, rhubarb is primarily produced in the states of [[Oregon]], [[Washington (state)|Washington]], and [[Wisconsin]] with approximately 1,200 acres in production, of which 175 are covered in hothouses.<ref>{{cite journal |title=Rhubarb |url=https://extension.oregonstate.edu/crop-production/vegetables/rhubarb |journal=Ag - Processed Vegetables |date=19 June 2018 |publisher=Oregon State University |access-date=18 November 2022|last1=Support |first1=Extension Web }}</ref> In the northwestern US states of Oregon and Washington, there are typically two harvests, from late April to May and from late June into July;<ref>{{Citation|author=Learn To Grow|title=How To Harvest Rhubarb|date=31 July 2015|url=https://www.youtube.com/watch?v=xU392gqTHLU| archive-url=https://ghostarchive.org/varchive/youtube/20211107/xU392gqTHLU| archive-date=2021-11-07 | url-status=live|access-date=17 May 2017}}{{cbignore}}</ref> half of all US commercial production is in [[Pierce County, Washington]].<ref>{{cite web|url=http://www.co.pierce.wa.us/pc/abtus/profile/agriculture.htm|archive-url=https://web.archive.org/web/20090731000751/http://www.co.pierce.wa.us/pc/abtus/profile/agriculture.htm|archive-date=31 July 2009|title=Pierce County Agriculture|date=31 July 2009|access-date=30 July 2018}}</ref> Rhubarb is ready to consume as soon as harvested, and freshly cut stalks are firm and glossy.

Rhubarb damaged by severe cold should not be eaten, as it may be high in [[oxalic acid]], which migrates from the leaves and can cause illness.<ref>
{{cite web|title=Growing Rhubarb in the Home Garden|publisher=Ohio State University Extension Fact Sheet|url=http://ohioline.osu.edu/hyg-fact/1000/1631.html|access-date=4 June 2013|archive-url=https://web.archive.org/web/20130605223334/http://ohioline.osu.edu/hyg-fact/1000/1631.html|archive-date=5 June 2013}}
</ref>

The colour of rhubarb stalks can vary from the commonly associated crimson red, through speckled light [[Variations of pink|pink]], to simply light green. Rhubarb stalks are poetically described as "crimson stalks". The colour results from the presence of [[anthocyanin]]s, and varies according to both rhubarb variety and production technique. The colour is not related to its suitability for cooking.<ref>{{cite web|url=http://www.rhubarbinfo.com/rhubarb-varieties.html |archive-url=https://web.archive.org/web/19990508142846/http://www.rhubarbinfo.com/rhubarb-varieties.html |url-status=usurped |archive-date=8 May 1999 |title=Rhubarb Varieties |publisher=Rhubarbinfo.com |date=1 September 2004 |access-date=5 March 2010}}</ref>

===Historical cultivation===
[[File:CSA-Rhubarb.jpg|thumb|right|A bundle of rhubarb]]
The Chinese call rhubarb "the great yellow" ({{transliteration|zh|dà huáng}} {{lang|zh|大黃}}), and have used rhubarb root for medicinal purposes.<ref name="mehta">{{cite web|url=http://pharmaxchange.info/press/2012/12/pharmacognosy-of-rhubarb/|title=Pharmacognosy of Rhubarb|author=Mehta, Sweety |date=27 December 2012|work=PharmaXChange.info}}</ref> It appears in ''[[Shennong Ben Cao Jing|The Divine Farmer's Herb-Root Classic]]'', which is thought to have been compiled about 1,800 years ago.<ref name=Lloyd>{{Cite book|url=https://books.google.com/books?id=apAPal8iAxgC&pg=PA270|title=Origin and History of All the Pharmacopeial Vegetable Drugs, Chemicals and Origin and History of All the Pharmacopeial Vegetable Drugs, Chemicals and Preparations with Bibliography|volume=1|author=John Uri Lloyd|year=1921|publisher=Read Books |isbn=978-1-4086-8990-5}}</ref> Though [[Dioscurides]]' description of {{lang|grc|ρηον}} or {{lang|grc|ρά}} indicates that a medicinal root brought to Greece from beyond the [[Bosphorus]] may have been rhubarb, commerce in the plant did not become securely established until [[Islamic Golden Age|Islamic times]]. During Islamic times, it was imported along the [[Silk Road]], reaching Europe in the 14th century through the ports of [[Aleppo]] and [[Smyrna]], where it became known as "Turkish rhubarb".<ref name=Warmington1928>{{cite book|last=Warmington|first=E. H.|title=The Commerce Between the Roman Empire and India|url=https://books.google.com/books?id=u9w8AAAAIAAJ&pg=PA207|year=1928|publisher=Cambridge University Press|location=Cambridge|isbn=978-1-00-136124-6|page=207ff}}</ref> Later,{{when|date=May 2024}} it began to arrive via new maritime routes and overland through Russia. The "Russian rhubarb" was the most valued, probably because of the rhubarb-specific quality control system maintained by the Russian Empire.<ref name="Monahan2013">{{Cite book| last = Monahan| first = Erika| chapter = Locating rhubarb |chapter-url=https://www.academia.edu/24221351 | title = Early modern things: objects and their histories, 1500–1800| editor-last = Findlen| editor-first = Paula| publisher = Routledge| isbn = 978-0-415-52051-5| pages = 227–251| location = Abingdon| date = 2013}}</ref> The 2020 edition of [[Pharmacopoeia of the People's Republic of China]] lists the following species as medicinally acceptable: ''[[Rheum officinale]]'', ''[[Rheum palmatum]]'', and ''[[Rheum tanguticum]]''.<ref>{{cite book |title=中国药典第一部 |page=24 |edition=2020 |url=https://db.ouryao.com/yd2020/view.php?id=f82dba38c5}}</ref> Grieve describes "Turkish rhubarb" as a mixture of ''R. palmatum'' and ''R. rhaponticum''.<ref name=Grieve/>

The cost of transportation across Asia made rhubarb expensive in medieval Europe.  It was several times the price of other valuable herbs and spices such as [[cinnamon]], [[opium]], and [[saffron]]. The merchant explorer [[Marco Polo]] therefore searched for the place where the plant was grown and harvested, discovering that it was cultivated in the mountains of [[Tangut people|Tangut]] province.<ref name=Lloyd/> The value of rhubarb can be seen in [[Ruy Gonzáles de Clavijo]]'s report of his embassy in 1403–1405 to [[Timur]] in [[Samarkand]]: "The best of all merchandise coming to Samarkand was from China: especially silks, satins, musk, [[ruby|rubies]], [[diamond]]s, [[pearl]]s, and rhubarb...."<ref>Quoted in {{cite book|author=Wood, Frances |title=The Silk Road: Two Thousand Years in the Heart of Asia|url=https://archive.org/details/silkroadtwothous0000wood|url-access=registration |year=2002|publisher=University of California Press|isbn=978-0-520-24340-8|page=[https://archive.org/details/silkroadtwothous0000wood/page/13 13]}}</ref>

The high price, as well as the increasing demand from apothecaries, stimulated efforts to cultivate the different species of rhubarb on European soil.<ref name="Monahan2013"/> ''R. rhaponticum'' × ''R. officinale'' came to be grown in England to produce the roots. ''R. alpinus'' was also allowed to grow wild.<ref name=Grieve>{{Cite web|series=A Modern Herbal 
| last= Grieve| first= M. | year= 1900
| title=Rhubarbs|url=https://botanical.com/botanical/mgmh/r/rhubar14.html|access-date=2023-02-23|website=botanical.com}}</ref> The local availability of the plants grown for medicinal purposes, together with the increasing abundance and decreasing price of sugar in the 18th century, galvanised its culinary adoption.<ref name="Monahan2013"/> Grieve claims a date of 1820 in England.<ref name=Grieve/> Rhubarb was harvested in [[Scotland]] from at least 1786, having been introduced to the Botanical Garden in [[Edinburgh]] by the traveller [[Bruce of Kinnaird]] in 1774. He brought the seeds from [[Abyssinia]] and they produced 3,000 plants.<ref>Grants Old and New Edinburgh</ref>

Though it is often asserted that rhubarb first came to the United States in the 1820s,<ref>Waters, Alice (2002) ''Chez Panisse Fruit''. New York: Harper Collins. p. 278. {{ISBN|978-0-06-019957-9}}</ref> [[John Bartram]] was growing medicinal and culinary rhubarbs in [[Philadelphia]] from the 1730s, planting seeds sent to him by [[Peter Collinson (botanist)|Peter Collinson]].<ref>{{Cite web|editor=David H
| last= Fry | first= Joel
|date=2012-07-20|title=Did John Bartram introduce rhubarb to North America?|url=https://growinghistory.wordpress.com/2012/07/20/did-john-bartram-introduce-rhubarb-to-north-america/|access-date=2023-02-23|website=Growing History|language=en}}</ref> From the first, the familiar garden rhubarb was not the only ''Rheum'' in American gardens: [[Thomas Jefferson]] planted ''[[Rheum undulatum|R. undulatum]]'' at Monticello in 1809 and 1811, observing that it was "Esculent rhubarb, the leaves excellent as Spinach."<ref>{{Cite web|date=2011-06-12|title=Rhubarb « Thomas Jefferson's Monticello|url=https://www.monticello.org/site/house-and-gardens/rhubarb|access-date=2023-02-23|archive-url=https://web.archive.org/web/20110612082720/https://www.monticello.org/site/house-and-gardens/rhubarb |archive-date=12 June 2011 }}</ref>

==Cultivars==
The advocate of organic gardening [[Lawrence D. Hills]] listed his favourite rhubarb varieties for flavour as 'Hawke's Champagne', 'Victoria', 'Timperley Early', and 'Early Albert', also recommending 'Gaskin's Perpetual' for having the lowest level of oxalic acid, allowing it to be harvested over a much longer period of the growing season without developing excessive sourness.<ref>Lawrence D Hills. Organic Gardening. Penguin 1997. page 145</ref>
[[File:Rhubarb Pie.jpg|thumb|right|A homemade [[rhubarb pie]]]]
The Royal Horticultural Society has the UK's national collection of rhubarb that comprises 103 varieties. In 2021–2022 this was moved from southern England to the more northern garden [[RHS Garden Bridgewater|RHS Bridgewater]] where winter cold and rainfall are better suited for rhubarb.<ref name="RHS-2022">{{cite web |title=RHS Bridgwater |url=https://www.instagram.com/p/CY4AQIOqXCK/ |website=RHS Garden Bridgewater Instagram |access-date=23 January 2022}}</ref> The following cultivars have gained the [[Royal Horticultural Society]]'s [[Award of Garden Merit]]:<ref>{{cite web 
| url= https://www.rhs.org.uk/plants/pdfs/agm-lists/agm-ornamentals.pdf | title = AGM Plants – Ornamental | date = July 2017 
| page = 84 | publisher = Royal Horticultural Society | access-date = 27 September 2018}}</ref> 
*'Grandad's Favourite'<ref>{{cite web | url = https://www.rhs.org.uk/Plants/102783/i-Rheum-i-×-i-hybridum-i-Grandad-s-Favorite/Details
| title = RHS Plantfinder – ''Rheum'' × ''hybridum'' 'Grandad's Favourite' | access-date = 23 September 2018}}</ref> 
*'Reed's Early Superb'<ref>{{cite web 
| url = https://www.rhs.org.uk/Plants/56251/i-Rheum-i-×-i-hybridum-i-Reed-s-Early-Superb/Details
| title = RHS Plantfinder – ''Rheum'' × ''hybridum'' 'Reed's Early Superb'
| access-date = 23 September 2018}}</ref> 
*'Stein's Champagne'<ref>{{cite web | url = https://www.rhs.org.uk/Plants/49497/i-Rheum-i-×-i-hybridum-i-Stein-s-Champagne/Details
| title = RHS Plantfinder – ''Rheum'' × ''hybridum'' 'Stein's Champagne' | access-date = 23 September 2018}}</ref> 
*'Timperley Early'<ref>{{cite web | url = https://www.rhs.org.uk/Plants/61820/i-Rheum-i-×-i-hybridum-i-Timperley-Early/Details
| title = RHS Plantfinder – ''Rheum'' × ''hybridum'' 'Timperley Early' | access-date = 23 September 2018}}</ref>

==Uses==
{{nutritional value
| name = Rhubarb, raw
| kJ = 88
| water = 94 g
| protein = 0.8 g
| fat = 0.3 g
| carbs = 4.54 g
| fiber = 1.8 g
| sugars = 1.1 g
| calcium_mg = 86
| iron_mg = 0.22
| magnesium_mg = 12
| phosphorus_mg = 14
| potassium_mg = 288
| sodium_mg = 4
| zinc_mg = 0.1
| manganese_mg = 0.196
| vitC_mg = 8
| thiamin_mg = 0.02
| riboflavin_mg = 0.03
| niacin_mg = 0.3
| pantothenic_mg = 0.085
| vitB6_mg = 0.024
| folate_ug = 7
| choline_mg = 6.1
| vitE_mg = 0.27
| vitK_ug = 29.3
| source_usda = 1
| note = [https://fdc.nal.usda.gov/food-details/167758/nutrients Link to USDA Database entry]
| copper_mg = 0.021
| selenium_ug = 1.1
}}
Rhubarb is grown primarily for its fleshy leafstalks, technically known as [[petiole (botany)|petioles]]. The use of rhubarb stalks as food is a relatively recent innovation. This usage was first recorded in 18th- to 19th-century England after affordable [[sugar]] became more widely available.<ref name="Monahan2013"/><ref name=Grieve/>

Commonly, it is stewed with sugar or used in pies and desserts, but it can also be put into savoury dishes or pickled. Rhubarb can be dehydrated and infused with fruit juice. In the United States, it is usually infused with strawberry juice to mimic the popular [[strawberry rhubarb pie]].

===Food===
The species ''[[Rheum ribes]]'' has been eaten in the [[Islamic Golden Age|Islamic world]] since the 10th century.<ref>{{Cite web|title=Andalusian Cookbook: Table of Contents|url=http://www.daviddfriedman.com/Medieval/Cookbooks/Andalusian/andalusian_contents.htm|access-date=2023-02-23|website=www.daviddfriedman.com}}</ref>

In Northern Europe and North America, the stalks are commonly cut into pieces and stewed with added sugar until soft.<ref>{{Cite book|last=Lyle|first=Katie Letcher|title=The Complete Guide to Edible Wild Plants, Mushrooms, Fruits, and Nuts: How to Find, Identify, and Cook Them|publisher=[[FalconGuides]]|year=2010|isbn=978-1-59921-887-8|edition=2nd|location=Guilford, CN|page=111|oclc=560560606|orig-date=2004}}</ref> The resulting [[compote]], sometimes thickened with corn starch, can then be used in pies, tarts and crumbles. Alternatively, greater quantities of sugar can be added with [[pectin]] to make [[Fruit preserves|jams]]. A paired spice used is [[ginger]], although [[cinnamon]] and [[nutmeg]] are also common additions.

In the United Kingdom, as well as being used in the typical pies, tarts and crumbles, rhubarb compote is also combined with whipped cream or custard to make rhubarb [[Fruit fool|fool]]. In the United States, the common usage of rhubarb in pies has led to it being nicknamed "pie plant", by which it is referred to in 19th-century cookbooks.<ref name="Bill Neal p. 308">{{cite book|author=Neal, Bill |title=Biscuits, Spoonbread and Sweet Potato Pie|page= 308 |publisher=Chapel Hill, NC: University of North Carolina Press|year= 2003|orig-date= 1990|isbn=978-0-8078-5474-7}}</ref> Rhubarb in the US is also often paired with strawberries to make strawberry-rhubarb pie, though some rhubarb purists jokingly consider this "a rather unhappy marriage".<ref name="Bill Neal p. 308"/>
[[File:2 kinds of Finnish Mead.jpg|thumb|right|Two varieties of ''[[sima (mead)|sima]]'': original (left) and rhubarb (right)]]
Rhubarb can also be used to make alcoholic drinks, such as [[fruit wine]]s or Finnish rhubarb ''[[sima (mead)|sima]]''. It is also used to make [[Kompot]].<ref>{{Cite web|title=Rhubarb Compote|url=https://www.bonappetit.com/recipe/rhubarb-compote|access-date=2023-02-23|website=Epicurious|date=7 April 2008 |language=en-US}}</ref>

===Nutrition===
Raw rhubarb is 94% water, 5% [[carbohydrate]]s, 1% [[protein (nutrient)|protein]], and contains negligible fat (table). In a {{convert|100|g|oz|frac=2|abbr=off|adj=on}} reference amount, raw rhubarb supplies {{convert|88|kJ|kcal|abbr=off}} of [[food energy]], and is a rich source of [[vitamin K]] (24% of the [[Daily Value]], DV) and a moderate source of [[potassium in biology|potassium]] (10% DV), with no other [[micronutrient]]s in significant amounts (table).

===Traditional Chinese medicine===
In [[traditional Chinese medicine]], rhubarb roots of several species were used as a [[laxative]] for several millennia,<ref name="Barceloux2012">{{cite book|last=Barceloux|first=Donald G|title=Medical Toxicology of Natural Substances: Foods, Fungi, Medicinal Herbs, Plants, and Venomous Animals|url=https://books.google.com/books?id=aTTBPedwFfAC&pg=PT235|date=2012|publisher=John Wiley & Sons|isbn=978-1-118-38276-9|page=235}}</ref> although there is no [[evidence-based medicine|clinical evidence]] to indicate such use is effective.<ref name=drugs/>

==Phytochemistry and potential toxicity==
The roots and stems contain [[natural anthraquinone|anthraquinones]], such as [[emodin]] and [[Rhein (molecule)|rhein]].<ref name="mehta" /> [[Emodin]] "represents a [[Genotoxicity|genotoxic]] risk for humans" while [[Rhein (molecule)|rhein]] is "a compound devoid of genotoxic capabilities".<ref>{{Cite journal |last1=EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS) |last2=Younes |first2=Maged |last3=Aggett |first3=Peter |last4=Aguilar |first4=Fernando |last5=Crebelli |first5=Riccardo |last6=Filipič |first6=Metka |last7=Frutos |first7=Maria Jose |last8=Galtier |first8=Pierre |last9=Gott |first9=David |last10=Gundert-Remy |first10=Ursula |last11=Kuhnle |first11=Gunter Georg |last12=Lambré |first12=Claude |last13=Leblanc |first13=Jean-Charles |last14=Lillegaard |first14=Inger Therese |last15=Moldeus |first15=Peter |date=January 2018 |title=Safety of hydroxyanthracene derivatives for use in food |journal=EFSA Journal |volume=16 |issue=1 |pages=e05090 |doi=10.2903/j.efsa.2018.5090 |pmc=7009633 |pmid=32625659}}</ref> The anthraquinones have been separated from powdered rhubarb root for purposes in [[traditional medicine]],<ref name="Barceloux2012"/> although long-term consumption of [[natural anthraquinone|anthraquinones]] has been associated with [[acute kidney failure]].<ref name="drugs">{{cite web |title=Rhubarb |url=https://www.drugs.com/npp/rhubarb.html |publisher=Drugs.com |access-date=26 January 2020 |date=13 May 2019}}</ref>

The rhizomes contain [[stilbenoid]] compounds (including [[rhaponticin]]), and the [[flavanol]] [[glucoside]]s (+)-[[catechin-5-O-glucoside|catechin-5-''O''-glucoside]] and (−)-[[catechin-7-O-glucoside|catechin-7-''O''-glucoside]].<ref name=Nonaka>{{cite journal|title=Flavanol glucosides from rhubarb and ''Rhaphiolepis umbellata''|journal=Phytochemistry|volume=22|issue=7|pages=1659–1661|doi=10.1016/0031-9422(83)80105-8|year=1983|last1=Nonaka|first1=Gen-Ichiro|last2=Ezaki|first2=Emiko|last3=Hayashi|first3=Katsuya|last4=Nishioka|first4=Itsuo|bibcode=1983PChem..22.1659N }}</ref>

===Oxalic acid===

Rhubarb leaves contain [[poison]]ous substances, including [[oxalic acid]], a [[nephrotoxin]].<ref name=drugs/> The long term consumption of oxalic acid leads to kidney stone formation in humans. Humans have been poisoned after ingesting the leaves, a particular problem during [[World War I]] when the leaves were mistakenly recommended as a food source in Britain.<ref>{{cite journal | last1 = Robb | first1 = H. F. | year = 1919 | title = Death from rhubarb leaves due to oxalic acid poisoning | journal = J. Am. Med. Assoc. | volume = 73 | issue = 8| pages = 627–628 | doi=10.1001/jama.1919.02610340059028}}</ref><ref>Cooper, M. R., Johnson, A. W. (1984). ''Poisonous plants in Britain and their effects on animals and man''. Her Majesty's Stationery Office, London, England. {{ISBN|978-0-11-242529-8}}</ref><ref>{{Cite web|title=Rheum x hybridum: The Poison Garden website |url=http://www.thepoisongarden.co.uk/atoz/rheum_x_hybridum.htm|access-date=2023-02-23|archive-url=https://web.archive.org/web/20200223042439/http://www.thepoisongarden.co.uk/atoz/rheum_x_hybridum.htm |archive-date=23 February 2020 }}</ref> The toxic rhubarb leaves have been used in flavouring extracts, after the oxalic acid is removed by treatment with precipitated chalk (i.e., [[calcium carbonate]]).

The {{LD50}} (median lethal dose) for pure oxalic acid in rats is about 375&nbsp;mg/kg [[body weight]],<ref>{{cite web|title=Rhubarb poisoning on rhubarbinfo.com|url=http://www.rhubarbinfo.com/rhubarb-poison.html|archive-url=https://web.archive.org/web/19991012022418/http://rhubarbinfo.com/rhubarb-poison.html|url-status=usurped|archive-date=12 October 1999}}</ref> or about 25 grams for a {{convert|65|kg|lb|adj=on}} human. Other sources give a much higher oral [[Lowest published lethal dose|LD<sub>Lo</sub>]] (lowest published lethal dose) of 600&nbsp;mg/kg.<ref>{{cite web | author = Safety Officer in Physical Chemistry | title = Safety (MSDS) data for oxalic acid dihydrate | publisher = Oxford University | date = 13 August 2005 | url = http://msds.chem.ox.ac.uk/OX/oxalic_acid_dihydrate.html | access-date = 30 December 2009 | archive-date = 7 January 2010 | archive-url = https://web.archive.org/web/20100107022344/http://msds.chem.ox.ac.uk/OX/oxalic_acid_dihydrate.html | url-status = dead }}</ref> While the oxalic acid content of rhubarb leaves can vary, a typical value is about 0.5%,<ref>{{cite journal|vauthors=Pucher GW, Wakeman AJ, Vickery HB |title=The Organic Acids of Rhubarb (Rheum Hybridum) |journal=Journal of Biological Chemistry|volume=126 |issue=1 |pages=43–54 |year= 1938|doi=10.1016/S0021-9258(18)73892-1 |doi-access=free }}</ref> meaning a 65&nbsp;kg adult would need to eat 4 to 8&nbsp;kg (9 to 18&nbsp;lbs) to obtain a lethal dose, depending on which lethal dose is assumed.  Cooking the leaves with [[Sodium bicarbonate|baking soda]] can make them more poisonous by producing soluble [[oxalate]]s.<ref>Everist, Selwyn L. (1974), ''Poisonous Plants of Australia''.  Angus and Robertson, Melbourne. p. 583. {{ISBN|978-0-207-12773-1}}</ref> The leaves are believed to also contain an additional, unidentified toxin,<ref>{{cite encyclopedia|url=https://www.medlineplus.gov/ency/article/002876.htm|title=Rhubarb leaves poisoning|encyclopedia=Medline Plus Medical Encyclopedia}}</ref> which might be an anthraquinone [[glycoside]] (also known as [[senna glycoside]]s).<ref>{{cite web|url=http://www.cbif.gc.ca/pls/pp/ppack.info?p_psn=171&p_type=all&p_sci=sci|title=Canadian Poisonous Plants Information System|publisher=Cbif.gc.ca|date=1 September 2009|access-date=5 March 2010|archive-url=https://web.archive.org/web/20090122112906/http://www.cbif.gc.ca/pls/pp/ppack.info?p_psn=171&p_type=all&p_sci=sci|archive-date=22 January 2009}}</ref>

In the [[petiole (botany)|petioles]] (leaf stalks), the proportion of oxalic acid is about 10% of the total 2–2.5% acidity, which derives mainly from [[malic acid]].<ref name=b1/> Serious cases of rhubarb poisoning are not well documented.<ref name="Barceloux2009">{{cite journal |last1=Barceloux |first1=DG |title=Rhubarb and oxalosis (Rheum species). |journal=Disease-a-Month  |date=June 2009 |volume=55 |issue=6 |pages=403–11 |doi=10.1016/j.disamonth.2009.03.011 |pmid=19446684|url=https://kundoc.com/pdf-rhubarb-and-oxalosis-rheum-species-.html|url-access=subscription }}</ref> Both fatal and non-fatal cases of rhubarb poisoning may be caused not by oxalates, but rather by toxic [[anthraquinone]] glycosides.<ref name=drugs/><ref name="Barceloux2009" /><ref name=savage1999>{{cite journal |last1=Noonan |first1=SC |last2=Savage |first2=GP |title=Oxalate content of foods and its effect on humans. |journal=Asia Pacific Journal of Clinical Nutrition |date=March 1999 |volume=8 |issue=1 |pages=64–74 |pmid=24393738 |url=http://apjcn.nhri.org.tw/server/APJCN/8/1/64.pdf|doi=10.1046/j.1440-6047.1999.00038.x }}</ref>

== Pests ==
Rhubarb is a host to the rhubarb curculio, ''[[Lixus concavus]]'', which is a [[weevil]]. Damage is mainly visible on leaves and stalks, with [[gummosis]] and oval or circular feeding and egg-laying sites.<ref>{{cite web|url=https://www.entomology.cornell.edu/cals/entomology/extension/idl/upload/Rhubarb-Curculio.pdf|title=Extension & Public Outreach|work=cornell.edu}}</ref>

Hungry wildlife may dig up and eat rhubarb roots in the spring, as stored starches are turned to sugars for new foliage growth.

== Cookbook ==
{{portal|Food}}
{{cookbook}}
* {{Cookbook-inline|Rhubarb Cake}}
* {{Cookbook-inline|Rhubarb Crumble}}
* {{Cookbook-inline|Rhubarb Fool}}
* {{Cookbook-inline|Rhubarb Juice}}
* {{Cookbook-inline|Rhubarb Marmalade}}
* {{Cookbook-inline|Rhubarb Pie}}
* {{Cookbook-inline|Rhubarb Pudding}}
* {{Cookbook-inline|Strawberry Rhubarb Pie}}

==Gallery==
<gallery>
File:Rhubarb at a market in Genoa.jpg|Rhubarb displayed for sale at a market
File:A 19th century apothecary jar for Rhubarb.jpg|A 19th-century [[apothecary]] jar for rhubarb
File:Strawberry Rhubarb, Dried Fruit.jpg|Dried strawberry-flavoured rhubarb
File:Phillips(1804) p649 - Russell Square - Rhubarb!.jpg|1804 illustration of a rhubarb seller in London
File:Mansikka-raparperipiirakka DSC08064 C.JPG|Old-fashioned strawberry-rhubarb pie
</gallery>

==References==
{{Reflist}}

==Further reading==
*Thompson, Fed S. [https://archive.org/stream/rhubarborpieplan00thom#page/n5/mode/2up Rhubarb or Pie Plant Culture], 1894. <small>([https://archive.org/details/rhubarborpieplan00thom/page/n6 <!-- pg=3 --> 1894])</small>
*Morse, J. E. [https://archive.org/stream/newrhubarbcultur01mors#page/n3/mode/2up The New Rhubarb Culture], 1901. <small>([https://books.google.com/books?id=L2BEAAAAYAAJ&pg=PR1 1901]) ([https://archive.org/stream/newrhubarbcultur00mors#page/n3/mode/2up 1903]) ([https://archive.org/stream/newrhubarbcultur00morsuoft#page/n5/mode/2up 1909])</small>
*Bland, Reginald. [https://archive.org/stream/winterrhubarbcul00blan#page/n3/mode/2up Winter rhubarb, culture and marketing], 1915.
*{{cite book|last=Foust| first = Clifford M.| title = Rhubarb: the wondrous drug|year = 1992| publisher = Princeton University Press| isbn = 978-0-691-08747-4}}

==External links==
{{Commons category|Rhubarb}}
{{Cookbook}}
*{{cite EB1911|wstitle=Rhubarb}}
* {{usurped|1=[https://web.archive.org/web/20150717121244/http://www.rhubarbinfo.com/ Rhubarb Info]}} from the {{usurped|1=[https://web.archive.org/web/19990125102749/http://www.rhubarbinfo.com/ Rhubarb Compendium]}}
{{Herbs used as laxatives}}
{{Taxonbar|from1=Q15600583|from2=Q7535}}
{{Authority control}}

[[Category:Rhubarb| ]]
[[Category:Medicinal plants]]
[[Category:Perennial vegetables]]
[[Category:Plants described in 1753]]
[[Category:Botanical taxa named by Carl Linnaeus]]
[[Category:Rheum (plant)]]
[[Category:Stem vegetables]]
[[Category:Nephrotoxins]]