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Summary

Rhubarb was introduced to the west as a laxative with restorative powers long before the consumption of the stalks as a dessert began but it is the leaves, deadly in 'normal' amounts, that earn it its place here.

Blog Entries

You can read more about Rheum, rhubarb, in these blog entries;
Investigating a story that rhubarb leaves were used to make a murder weapon
The one word error that may have cost lives

Family

Polygonaceae

Meaning of the Name

Rheum
Some people assume there is a connection between the Rhubarb plant and rheumatism but there is not. Rheumatism comes from Latin whereas the plant name comes from the Greek name ‘Rheon barbaron’ meaning ‘from the barbarous lands of Rha’, the Greek name for the Volga river.
 
hybridum
A cross between two species.

Common Names and Synonyms

rhubarb

How Poisonous, How Harmful?

Rheum x hybridum, rhubarb

Though the stalks are widely eaten as a dessert, the leaves are highly toxic. They contain oxalic acid in the form of oxalates which is widely believed to be the poison but there is evidence that these are insufficient to cause the known fatalities. There are reasons to believe that it is anthraquinone alkaloids which are to blame but the mechanisms have not been fully studied.

In 1945, in the New England Journal of Medicine, Jeghers and Murphy, when discussing the issue of whether oxalates are wholly to blame for rhubarb's fatal poisonings note that 'There is a distinct paucity of reliable information on this subject in the modern literature'. They go on to encourage any physicians who encounter rhubarb poisoning to publish a case study to make a 'worth-while contribution to the medical literature'. Sixty plus years later, we are no better informed. There appears to have been only one case study, published in 1960, and its title, 'Death of a child from oxalic acid poisoning due to eating rhubarb leaves', suggests the authors did not find anything to add to the understanding.

Either the modern incidence is extremely low or the cases do not get reported as Jeghers and Murphy hoped they would.

Symptoms of rhubarb poisoning are said to be, weakness, burning in the mouth and throat, breathing difficulty, pain in the eyes and stomach, nausea, vomiting, diarrhoea, seizures, red coloured urine and kidney stones. Death from eating rhubarb leaves occurs quickly and is preceded by drowsiness, possibly leading to coma, convulsions, internal bleeding and nosebleeds as coagulation is inhibited. Symptoms may begin within an hour of ingestion though in some older cases onset took much longer.

Incidents

A visitor to the Alnwick Garden Poison Garden reported that the family's goats had been poisoned by rhubarb leaves after the vicar threw them over the fence into the field where the goats were.

Another visitor said that, when she was a child, she had fed her pet albino rabbit on rhubarb leaves and killed it.

Folklore and Facts

Though stories told by visitors to the Alnwick Garden Poison Garden were always interesting to hear, they were frequently wrong. The rhubarb provides two good examples of such stories.

A visitor claimed that Captain Cook had been the first person to realise the role of green vegetables in preventing scurvy which meant he had the first scurvy free vessel in the navy. Unfortunately, when other green leaves were not available he fed his crew on rhubarb leading to many deaths. In fact, Cook’s vessel suffered almost as many scurvy deaths as other vessels in the fleet in spite of his attempts to provide fresh fruit and vegetables. I can find no reference to his men being fed rhubarb leaves.

Another visitor stated, as fact, that the mixture of rhubarb and pineapple is deadly. This is not so. There are numerous recipes available for rhubarb/pineapple pie. The suggestion is that the acid in pineapple combines with the small amount of oxalic acid in rhubarb stems to produce a harmful strength. The acids in pineapples, which are not oxalic acid, could break down the cell walls of rhubarb and increase the bioavailability of the small amount of oxalic acid in the rhubarb. This could increase the acid taste but would not affect the absorption.

The peak for rhubarb production in the Wakefield area came during the two world wars. Because rhubarb will take on the flavour of other substances many jams and marmalades were made with a high rhubarb content. ‘Raspberry’ jam was around 60-70% rhubarb. It is said that there was a company in Bradford making wooden raspberry seeds to put in the jam to improve its looks but I haven't been able to find any proof of this.

Closer to the truth was the visitor who said rhubarb leaves had been recommended as a green vegetable during wartime shortages. I've heard this said by a number of people and they almost always say this happened in WWII. I've searched for any information on this and only found one reference.

The Canadian Biodiversity Information Facility (formerly the Canadian Poison Plants Information Service) website says that ‘ingesting rhubarb leaves has caused many fatalities, especially during World War II, when the leaves were recommended as food for a short time’. This seems to be the only reference to rhubarb leaves being used in the UK during WWII and could be a typing error because, elsewhere on the same page it says 'Human poisoning was a particular problem in World War I'.

However, on the BBC’s ‘People’s War’ website a woman talks about being 12-years old in occupied France and eating rhubarb leaves as a vegetable until there was an announcement in the press that this could cause poisoning. If such poisonings did occur in France during WWII that might explain why it is a Canadian organisation that refers to it.

Mrs Grieve

Maud Grieve, usually referred to simply as Mrs Grieve, was a leading herbalist in the early 20th century.  She used her garden in Chalfont St. Peter, Buckinghamshire in the growing and preparation of herbs. During the First World War medicinal herbs were an important substitute for the manufactured medicines which could not be obtained and Mrs Grieve set down her knowledge in a great many pamphlets.
 
In the 1920s, Hilda Leyel, founder of the Society of Herbalists, organised these pamphlets into a book and added American herbs, at the insistence of the publishers. ‘A Modern Herbal’ was published in 1931 and combines allusions to the old herbals alongside ‘modern’ uses of the plants and some anecdotal remedies.

Mrs Grieve is a frequently used source for plant information which is unfortunate, as much of what she writes is inaccurate. Two examples will suffice. She says the Atropa belladonna berry is 'intensely sweet' whereas the taste is slightly sweet but insipid. Also, she says aconite was the poison used on Ceos when this was poison hemlock.

There are, however, a number of references to problems during World War I when rhubarb leaves had been recommended as a vegetable until a number of deaths occurred and the advice was withdrawn.

Rheum x hybridum, rhubarb

Mrs Grieve talks about a letter in the Gardeners Chronicle for 1846 in which the gardener of the Earl of Shrewsbury at Alton Towers, Staffordshire, told how rhubarb leaves had been used there for many years as a vegetable. Then he wrote again to correct it and say it was the leaf-stalks he meant. It is possible that this error might have been passed down leading to the misuse of the leaves.

Obviously, in a printed magazine there is no way make an amendment. All that can be done is to announce a correction but, if someone only sees the original piece, they will not know about the amendment. In the electronic era, it should be easier to show corrections but that relies on people accepting that a correction is required.

A few years ago, a television programme about the medicinal uses of plants included a herbalist saying that it was remarkable the rhubarb had dual properties because it had been used to treat constipation and diarrhoea. That statement missed the key point that for a long time it was thought that the way to cure diarrhoea was to give the sufferer a 'purge' and clear them out of whatever was causing the looseness.

In 1254, William of Rubruck was travelling in the Mongol empire and met an Armenian monk who claimed that root of rhubarb cut small and mixed with water would, when used in conjunction with a cross the monk had, determine whether a sick person would recover or die.

If his determination indicated survival, he would give the water to the patient and the strong laxative effect would produce a remarkable physical reaction often perceived as a miracle.