by Ian Duggan
Despite the danger of rhubarb leaves being known for over one hundred years, their consumption remains one of the most highly reported causes of poisoning by plants in New Zealand. Based on data from the New Zealand National Poisons Centre collected between 2003 and 2010, for example, rhubarb was ranked as the eighth most reported cause of poisoning by plants to its phone centre, representing 121 phone calls, of which 76% was from consumption by children.[i]

The widespread use and popularity of rhubarb in Great Britain began in the early 19th Century,[ii] and its import to New Zealand likely occurred not long after. Indeed, newspaper advertisements for rhubarb in New Zealand can be found as early as 1840.[iii]
The first reports in New Zealand newspapers of death by the ingestion of rhubarb leaves came from a curious case in England in 1917. At this time, during World War I, rhubarb leaves were being recommended in Great Britain a substitute for green vegetables due to wartime shortages.[iv]
Here, it was reported that a Presbyterian minister, a Rev. W. R. Colville, had died in Enfield Cottage Hospital, north of London, five days after he had consumed rhubarb leaves that were “cooked as cabbage”. It was noted, contrary to previous advice, that “the public would be well advised to refrain from indulging in rhubarb leaves as a substitute for spinach or cabbage”. Poisoning by oxalic acid was suggested by the British Medical Journal as the explanation of cases of poisoning from eating rhubarb leaves.[v],[vi]
News continued to filter through to New Zealand on this case. At the inquest, it was reported, expert opinion on the dangers of using rhubarb leaves as a food was provided by Mr J. Webster, a pathological chemist and assistant analyst to the Home Office, who presented an analysis of the rhubarb leaves taken from the same ground as those from which the deceased ate, which showed that oxalic acid was present. Dr Spilsbury, who made the post-mortem, found fatty degeneration of the heart and liver, apparently due to poison. Death was thus concluded to be due to poisoning from the oxalic acid contained in the leaves. The coroner, a Mr Forbes, said the case was important, because people economising on food were using food substitutes: “If using rhubarb leaves involved risk, the public should know it, and the present inquiry should be given the fullest publicity. Considerable harm had been caused by advising the people to eat rhubarb leaves”. However, “Nothing need prevent the use of stalks as fruit”.[vii]
Overall, this report was among the first to provide an appreciation of the dangers of eating rhubarb leaves in Great Britain, and among the colonies. Nevertheless, prior to this, a number of illnesses and deaths had been reported in New Zealand relating to consumption of rhubarb, some of which may ultimately have been the result of oxalic acid via consumption of the foliage. In particular, a series of 1885 articles concerned a boy “who had died at Oamaru from poisoning resulting from eating green rhubarb tops”.[viii]
Here, it was reported that a “boy, aged eight years, died suddenly on Sunday morning. An inquest was held today, at which the medical evidence gave the cause of death as poisoning. It appears that the boy had eaten green rhubarb tops on Saturday last, and on Saturday night and Sunday morning was taken ill with vomiting and purging. The post mortem examination revealed the fact that the irritation caused by eating the rhubarb had brought about congestion of the brain”.[ix] At this time, the effects were thought to be because the “rhubarb tops… had been lying on a galvanised iron roof for some time, and were slightly decayed”[x]

Regular stories of rhubarb poisoning in New Zealand continued from there, though not always linked to consumption of leaves. Often, illness was put down to improper preservation. In 1872, for example, it was reported that “A family in Greytown had a narrow escape from poisoning from eating preserved rhubarb. Severe symptoms for a time existed, but ultimately they recovered under the care of Dr Welch”. The newspaper noted, “It is remarkable how people will persist in eating imported preserves of any kind, when, by a trifling expenditure of money and labor [sic], they can produce a much superior article. Extreme care should always be taken that the part next the tin be not eaten. The acid of preserves dissolves the tin, producing in some cases a deadly poison”.[xi]
A similar story emerged in 1878: “A singular case of fruit poisoning came under our notice a few days ago!”, exclaimed the Thames Advertiser. “A family were enjoying a pie made of rhubarb which had been preserved in tins, when they commenced to feel very sick, and afterwards vomiting ensued. An inquiry into the cause of the sickness resulted in one of the members of the family taking up the tin and finding that some of it was crusted over with rust, the acid having eaten away the tin, which was in solution, causing the sickness. The attack was a very severe one, and continued for the space of an hour, not ceasing until, by the aid of emetics, the poisoned fruit had been removed”.[xii]
In 1898, a serious case of poisoning was reported, affecting six Auckland residents. There, “an elderly couple named Mr and Mrs Colvin, their son Thomas Colvin, aged 20 years, a married daughter named Mrs Page, and two grandchildren, were all taken so seriously ill that Dr. Lewis was sent for”. It was determined that the family were suffering from “ptomaine poisoning” [xiii] – a now obsolete term relating to food poisoning caused by bacteria or their toxins. An investigation by a Dr Lewis indicated that the illness was due to a rhubarb pie that had been kept in a ‘close safe’ near the fireplace, which had fermented.[xiv] Thankfully, all of the family completely recovered.[xv]
While other similar stories exist, a large amount of coverage and correspondence was given to a major food poisoning case in Christchurch following the consumption of rhubarb in 1968, which suggested that some of the previous cases of food poisoning may have actually been the result of consuming oxalic acid from the leaves.
There, the Health Department reported 126 cases of food poisoning in one week, with rhubarb blamed for most of them: “…120 adults at an institution suffered from food poisoning in which the food eaten in common was rhubarb”. Symptoms including nausea, vomiting and diarrhoea. A Mr Snoad, the supervising district inspector of health, noted that the “green leaves and any green portions of the stalks of rhubarb normally contain oxalic acid which is toxic and would cause these symptoms If consumed”, indicating he believed that he may have thought consumption of the foliage may have been the cause. However, he broadened the possibility by stating, “Also it is thought by some people that ‘first-of-the-season’ rhubarb tends to be somewhat of an irritant of which too much should not be eaten”. The report was clear with caution, stating that, “When preparing rhubarb always discard the leaves and green portions of the stalks. The red portions of the stalks are quite safe to cook and eat in moderation.”[xvi] Indeed, following tests, Mr Snoad stated that although the result of the analysis of the only sample available was not as clear as he had hoped it would be, it pointed strongly to oxalic acid as the cause. He reiterated at this point that “people should not eat the green parts of rhubarb stalks, nor use the leaves as a substitute for spinach”.[xvii]

Being such a notable event, much correspondence followed in Christchurch newspaper, The Press.
An Isabella C. Brown wrote to say that she was “surprised to learn that many Christchurch people have been suffering from food poisoning after eating rhubarb”. She believed that most people would be aware that the veins and leaves of rhubarb contain oxalic acid, and she had thus never before heard of anyone being poisoned by eating them. Her main concern, however, appeared to have been of the danger of potatoes: “instead of being sold in paper bags or other safe containers all potatoes are now sold in transparent plastic bags, fully exposed to the light. I have no doubt that many other cases of food poisoning could be traced to eating green potatoes. The practice of storing them in plastic bags should be discontinued”. The Medical Officer of Health, Dr L. F. Jepson, however, responded that they did not “consider the packing of potatoes in plastic bags hazardous”.[xviii]
This was followed soon after by correspondence from someone using the moniker “Rhubarb”, concerned by the negative publicity from the recent press: “Because of the adverse publicity given rhubarb recently after cases of poisoning, our sales of spring rhubarb, on which we usually depend for our rates money, have been severely cut down. We would like to have it made clear that, provided rhubarb is cooked properly —without using any of the green leaf—it is quite safe and will incur no risk of poisoning.[xix]
Further correspondence followed, including a theory by “No Sago” that the poisoning had possibly been caused by the consumption of the combination of rhubarb and sago.[xx] E. D. P., in response, responded that “During World War I rhubarb leaves were freely used as spinach. However, there were some cases of poisoning and the public were warned not to use baking soda (sodium bicarbonate), as the addition made the leaves poisonous”. They pondered, “As far as rhubarb and sago are concerned, I often cook both together, as for apple sago, and it makes a pleasant dish. It has never upset any of us. Is it possible that “No Sago” could have confused soda with sago?”[xxi]
These continued communications worried some. “Not Indisposed” wrote, “As you may be aware considerable correspondence has ensued after the recent case of rhubarb poisoning. I have failed to note any replies or statements on the matter by more competent authorities and wonder if you could perhaps discuss this aspect in your column as it would undoubtedly make the position clearer to many of us, including myself, who grow or buy and consume it”.[xxii]
The Press reminded the readers at this point that, indeed, the “Christchurch Health Department issued a statement on the matter shortly after the incident occurred which I think should have quelled any misgivings about rhubarb”, adding, “Dr Connor, in his publication “Poisonous Plants in New Zealand,” states that “the leaf stalks of rhubarb are edible but care must be taken not to include the leaves”.[xxiii] And, with a sense of finality, followed with, “[This correspondence is now closed.—Ed., “The Press.”].” [xxiv]
References
[i] Slaughter, R.J., Michael, D., Beasley, G., Lambie, B.S., Wilkins, G.T. & Schep, L.J. (2012). Poisonous plants in New Zealand: a review of those that are most commonly enquired about to the National Poisons Centre. New Zealand Journal of Medicine 125: 87-118.
[ii] Foust, C.M. & Marshall, D.E. (1991). Culinary Rhubarb Production in North America: History and Recent Statistics. HortScience 26:1360-1363.
[iii] New Zealand Advertiser and Bay of Islands Gazette, 3 September 1840, P2
[iv] Yamaguchi, M. (1983). Toxic Substances and Folk Medicinal Uses of Vegetables. In: World Vegetables. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-7907-2_5
[v] Rhubarb Leaves. Mataura Ensign, 6 July 1917, P5
[vi] Entre Nous. Free Lance, 3 August 1917, P11
[vii] Dangers of Rhubarb Leaf. Evening Star, 26 July 1917, P4
[viii] Table Talk. Auckland Star, 30 September 1885, P2
[ix] Singular Death of a Boy. Evening Post, 30 September 1885, P2
[x] North Otago Times, 30 September 1885, P2
[xi] Wellington Independent, 24 December 1872, P2
[xii] Thames Advertiser, 22 August 1878, P2
[xiii] Serious Poisoning Case. Auckland Star, 10 January 1894, P5
[xiv] Accidents and Fatalities. Press, 10 January 1894, P5
[xv] New Zealand Herald, 19 January 1894, P4
[xvi] Five Outbreaks of Food Poisoning. Press, 1 October 1968, P12
[xvii] Poisoning From Acid In Rhubarb. Press, 4 October 1968, P1
[xviii] Potatoes. Press, 11 October 1968, P12
[xix] Rhubarb. Press, 12 October 1968, Page 12
[xx] Rhubarb Or Sago. Press, 21 October 1968, P12
[xxi] Rhubarb Or Sago. Press, 23 October 1968, Page 18
[xxii] Gardeners’ Queries. Press, 25 October 1968, Page 6
[xxiii] Gardeners’ Queries. Press, 25 October 1968, Page 6
[xxiv] Gardeners’ Queries. Press, 25 October 1968, Page 6


































