rhubarb

Rheum x hybridum
 
February


U.K.
 


Wakefield Rhubarb Festival 

 

25th - 27th February 2022
 
Held in Wakefield's city centre, the Rhubarb Festival, which incorporates a market featuring other locally produced food and drink, offers rhubarb, both freshly harvested and in processed form, in everything from preserves and salad dressings to hand and body wash. Also on offer during this year's festival will be gin tastings involving 'rhubarb cocktails', cookery demonstrations and a 'Rhubarb Trail' around the city, with restaurants and bars providing rhubarb-themed food and drinks.

[https://experiencewakefield.co.uk/event/rhubarb-festival/]

Not to be missed when available - cancelled for 2022 due to Covid but expected to resume in 2023 - is 'Oldroyd's Rhubarb Triangle Experience', an opportunity to see how forced rhubarb is produced via a tour which must be booked in advance.
 
Janet Oldroyd Hulme (affectionately known as 'the High Priestess of Rhubarb', so passionate is she about this remarkable plant), carries on a long tradition of forced rhubarb production, begun by her great grandfather, at her farm, located in Carlton village, some 5 miles from Wakefield.  Now one of only a few growers left in the region, she is the fourth generation of the family to grow rhubarb in Yorkshire's famous Rhubarb Triangle - an area bounded by Bradford, Leeds and Wakefield.
 
Full of enthusiasm and information about the ancient history and medicinal benefits of the plant, it's Janet's passion and commitment and her fascinating tours that have played a significant part in popularizing forced rhubarb today.

The visit begins with a talk covering everything from the origins of rhubarb cultivation to its past and present potential medicinal uses. This is followed by a tour of a forcing shed, an eerie, magical experience, as one enters a warm, cavernous space, entirely dark except for the light cast by candles, containing up to 14,500 rhubarb plants. We're told that if we stand quietly, we may be able to hear the rhubarb growing (at up to an inch a day) as the furled leaf buds burst open with soft pops.


The Curious History of Forced Rhubarb

 

The culinary rhubarb Rheum x hybridum, whose fleshy leaf stalks we use today as a food, is a hybrid plant with origins that are not clearly understood.

A member of the dock family, the Polygonaceae, 55 species of Rheum are currently listed by Plants of the World OnLine - an international collaborative programme which aims to make digitized data of the world’s flora available - with a native distribution from Bulgaria to temperate Asia and northern Indo-China.(1) A different source reports that 39 species and 2 varieties are found in China, mostly concentrated in the northwest and southwest of the country, which is regarded as the 'distribution center of rhubarb'. (2) 

 

While some confusion has arisen because of the number of different plants that have over time, been given the name 'rhubarb', some of these species were being used thousands of years ago and have continued to be used in Asia, not as foods, but as important medicinal plants. The first recorded use of a plant referred to as rhubarb, in a Chinese herbal, dates back to 270 BCE. (2)  The medicinal compounds were extracted not from the stalks but from the rhizomes of the plants as a source of treatments for a range of ailments, including those of the gut, lung and liver. (3)

The Romans are said to have used a rhubarb root in powdered form which was associated in origin with the Siberian region of the River Volga as a purgative, and this use was to continue as the drug made its way much later across Europe, after its description and use by Marco Polo (who wrote that it grew 'in great abundance' in the mountains of northwest China) at the end of the 13th C.(4)

 

Administered in dried and powdered form as a gentle laxative, it was available in Britain from the 16th C, imported from Asia (though during the 18th C largely from Russia) and is mentioned in Shakespeare's Macbeth.  Extremely expensive however, a search began to find the best medicinal plants so that rhubarb could be grown at home. R. rhabarbarum and R. rhaponticum are two such 'species' that are referred to as having being grown in Europe before the 18th C for medicinal use.(4)  It was discovered however that the stems of certain kinds of rhubarb (and in particular the above), could be eaten, and plants, raised from seeds, were being grown for this purpose by the beginning of the 19th C. Although not an initial success, cooking with sugar, which had become much cheaper by this time, made rhubarb stems much more popular as a food, and in particular as an ingredient of puddings and pies.

A chance discovery however, made at around this time in London's Chelsea Physic Garden, where rhubarb was being grown as a medicinal plant, was to transform the way it would be eaten henceforward.  In 1817, some workmen who had earlier thrown soil from a trench they were digging over some dormant rhubarb roots, discovered on refilling the trench, that pink shoots were emerging from the earth.  
 
These stems - technically a vegetable, but treated as a fruit -  proved to be so much more palatable - much more tender and less sour than rhubarb grown naturally - that the method of producing it in this way soon took hold. The fruit most people ate over winter at this time had had to be stored, but forced rhubarb now offered a fresh and delicious alternative. Growers in London began to produce rhubarb by covering it with soil or manure (technically 'blanching' rather than forcing it), some bringing roots inside buildings for the process.

The true 'forcing' of rhubarb, that is, growing it out of its natural season in special heated sheds, began in Yorkshire in 1877. The heavy soils and moist, cool conditions of the region - cold making the stems sweeter (early frost in October also important for the forcing process) were perfect for the development of the root systems needed.  With abundant supplies of coal available for heating the growing sheds which could keep the plants warm (today, around 65 degrees F) and dark, and with a cheap and abundant source of nitrogen feed (in the form of 'shoddy' - waste wool - supplied by the flourishing wool industry) a group of local producers (200 at their peak) in the region between Leeds, Wakefield and Bradford (to become known as 'the rhubarb triangle') were able to produce rhubarb before anyone else in Britain. This area became the centre for the world's production of forced rhubarb.

Forced rhubarb became so popular that by the late 19th C it was being sent nightly by train to Covent Garden and Spitalfields markets in London, as well as to further destinations in Europe. At this time West Yorkshire produced some 90% of the world's winter-forced rhubarb. By the time of WW2 forced rhubarb had almost become a national institution in Britain and part of the staple diet. To keep it affordable for ordinary people during the War its price was controlled by the government and kept at a shilling per pound. 
 
The wartime rationing of sugar with which to sweeten it however, prompted it's decline and after WW2 the ready availability of a new range of fruits from overseas brought disaster for the Yorkshire growers, causing most to give up or go out of business. The dedicated efforts of Ken Oldroyd who set up the Yorkshire Rhubarb Growers Association in 1967, which enabled growers to market their produce as a group, was a key step in reviving the fortunes of forced rhubarb - today widely appreciated once more.

References:

1. Royal Botanic Garden, Kew. 'Plants of the World OnLine

[https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:32581-1]

2. Xiang, H., Zuo, J., Guo, F. et al. What we already know about rhubarb: a comprehensive review. Chin Med 15, 88 (2020). https://doi.org/10.1186/s13020-020-00370-6

 

3. www.yorkshirerhubarb.co.uk/rhubarb_triangle.htm]

4. Roberts, J., Cabbages |& Kings: the origins of fruit and vegetables, Harper Collins, 2001, p 115.

Main sources for the history of forced rhubarb: [www.yorkshirerhubarb.co.uk/rhubarb_triangle.htm],

Mahon, S., 'A Tour de Forcing', The Edible Garden, Autumn/Winter 2012, pp 109 -112

FEB30277.JPG

Rhubarb stems growing in candle light, near Wakefield


Producing Forced Rhubarb
The commercial forcing carried out by the Oldroyd family business today (one of England's largest rhubarb producers) is a long, painstaking process which has required many years of work to establish and needs considerable effort to maintain. 
 
Roots that have had their carbohydrate reserves built up after two summers outside (having been well fed and kept weed-free, whilst their leaves have been removed) are levered out of the ground (some of them requiring three men to lift them) and brought into the forcing  sheds, where they are carefully positioned on a thin layer of soil.  

These sheds are kept completely dark but heated - the absence of light and the warmth prompting the well-fed roots to quickly produce bright pink, yellow-leaved stems that are very sweet. Because they are deprived of light the stems don't develop any chlorophyll so remain white on the inside rather than green, and when cooked take on the beautiful pink colour of their outer skin. They plants are not fed whilst in the sheds, just given heat and water.

Commercially grown forced rhubarb - of which several varieties, including 'Timperley Early' and 'Reed's Early Superb', have been developed - is propagated from a root not from seeds, as the plant won't come true. According to Janet Oldroyd, the variety known as 'Stockbridge Arrow' is regarded as the best in the forcing industry in terms of quality and yield. 
 
While threats to the plants inside the sheds come most notably in the form of attacks of botrytis - the warm damp conditions helping the spread of fungal spores - outside, climate breakdown may come to have a serious effect on the plant's ability to produce at all. Excessive rain - and at the wrong time -and lack of frost at the right time (frost is essential for prompting the convertion of stored energy within the root into glucose) has caused significant reductions in production.

Yorkshire Forced Rhubarb now has Protected Designation of Origin status.


[www.yorkshirerhubarb.co.uk/rhubarb_triangle.htm]
[Mahon, S., 'A Tour de Forcing', The Edible Garden, Autumn/Winter 2012, pp 109 -112]
Ellis, H., 'An Irresistible Force', Kew, Spring, 2006, pp 48 -50]
    
 

Rhubarb - a store of useful compounds

While Oriental medicinal rhubarb has been used in traditional Chinese medicine for thousands of years, the potential health benefits of British garden rhubarb have also been the subject of recent research.  

High in oxalic acid (in leaves and roots), it has been hailed by some as potentially useful in preventing certain cancers. Research conducted by scientists at Sheffield's Hallam University and the Scottish Crop Research Institute found that baking rhubarb for 20 minutes significantly increased its levels of polyphenols - chemicals which include a group of compounds known as anthraquinones - and antioxidants, that can selectively kill or prevent the growth of certain cancer cells.

Dr Nikki Jordan-Mahy, from Sheffield Hallam University's Biomedical Research Centre reported: "Our research has shown that British rhubarb is a potential source of pharmacological agents that may be used to develop new anti-cancerous drugs."

Gordon J. McDougall, Pat Dobson, Nikki Jordan-Mahy, Effect of different cooking regimes on rhubarb polyphenols, Food Chemistry, Volume 119, Issue 2, 2010, Pages 758-764,[https://doi.org/10.1016/j.foodchem.2009.07.030].[https://www.sciencedirect.com/science/article/pii/S0308814609009194)]

Derivatives of anthraquinones are also reported to be able to 'play a therapeutic role in [the treatment of] central nervous system diseases'. 

Xun Li, Shifeng Chu, Yinjiao Liu, Naihong Chen, "Neuroprotective Effects of Anthraquinones from Rhubarb in Central Nervous System Diseases", Evidence-Based Complementary and Alternative Medicine, vol. 2019, Article ID 3790728, 12 pages, 2019. [https://doi.org/10.1155/2019/3790728]

 

Scientists have been looking too, into the compound parietin, the orange pigment found within rhubarb and also in lichens, as a possible source of anti-cancer drugs.

[Eastman, Q., & Fortin., J. Orange lichens are source for potential anti-cancer drug,  Woodruff Health Sciences Center, Oct. 19, 2015 

[http://news.emory.edu/stories/2015/10/winship_chen_pigment/]

In 1996 it was reported that sodium oxalate, found in rhubarb leaves could be used, when heated 'at about the temperature for baking bread' to convert 'stockpiles of the CFC chemicals that damage the Earth's protective ozone layer into salt, carbon and ... sodium flouride'.

[Highfield, R., Rhubarb Can Save the Ozone Layer', The Daily Telegraph, January 20, 1996]

Rhubarb products Wakefield.jpg

Vinegar, Cordial and Jelly all incorporating rhubarb, sold at the Wakefield Rhubarb Festival