Editing Rhubarb (section)

==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}}
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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>