Rhubarb is the stalk of a leafy perennial plant.
It is actually a vegetable, not a fruit. We usually treat it as a fruit, because of its high acidity, but some cultures do use it as a vegetable in savoury dishes, so don’t be entirely surprised if you come across such recipes.
The leaves are extremely poisonous. They contain in abundance a toxic amount of oxalic acid, which causes cramps, nausea, and often, death. Apparently, someone in living memory has actually tasted them and lived, so we know that they don’t taste very good anyway (they are very bitter.) Don’t let the leaves put you off rhubarb, though: potato and tomato leaves would kill you, too.
We mostly use rhubarb for desserts, in pies, puddings and stewed sweet sauces. Don’t feel, however, that you can only use that sauce on your cheesecake: rhubarb sauce is also really amazing with pork, lamb and pâtés. You can also make rhubarb chutney, flavoured with ginger, orange zest, brown sugar, and sultanas. Rhubarb jam makes a good filling for layer cakes and cookies. You can also roast it in chunks, accompanying root veg such as carrots and parsnips.
Rhubarb always needs to be sweetened, but be careful not to go overboard — part of the appeal of rhubarb should be its underlying tartness. Strawberries are the usual favourite fruit to mix with rhubarb. Rhubarb also goes great with raspberries, currants, black berries, apricots and peaches. But just as with sweetening it, it’s easy to overwhelm the flavour of the rhubarb with other fruit.
The bright-red stalk rhubarb is the one that we are most familiar with (called by monikers which are variations of “Crimson” or “Cherry”, depending on where you live.) It has the tartest stalks. Rhubarb can also be bought with pink, light-red, green or white stalks (see entry for Champagne Rhubarb.) The redder the stalk, the more sour it will be. Hothouse rhubarb, the kind you mostly see in stores during the winter, will have lighter-coloured stalks, be less sour and be less stringy than garden or field rhubarb.
When buying rhubarb, pick firm stalks; avoid limp ones that are on their way out. As with many things in life, firmness can be a better indication of quality than size.
Rhubarb is a rarity in the American south, because it does not like warm climates.
Allow rhubarb to grow for two years untouched before harvesting. You can start harvesting it in the third year. In that third year, you can harvest for up to 4 weeks at the start of the season. By its fourth year, and after, you can harvest stalks for 8 to 10 weeks. Stop harvesting rhubarb by mid-June, leaving at least 1/3 of the stalks. The plant needs this to store strength in the roots to produce a good crop next year. Jauraon, Richard. Answers to Frequently Asked Rhubarb Questions. Iowa State University Extension. 14 May 2004. Accessed June 2016 at .http://www.ipm.iastate.edu/ipm/hortnews/2004/5-14-2004/rhubarb.html
Opinions as to whether you can harvest in the fall — because the stalks would die anyway — vary. The USDA says you can. They say, “Select young, tender, well-colored stalks from the spring or late fall crop.”  Rhubarb – Stewed. United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2009. Page 2-22.. Some bloggers suggest that if you do, harvest only about a third of the stalks at a time.
Other authorities say that harvesting in the fall is not a good idea: ” Harvest in the fall only when the plants are to be discarded the next season.” Wolford, Ron. University of Illinois Extension. Watch your garden grow: rhubarb. Accessed June 2016 at .https://extension.illinois.edu/veggies/rhubarb.cfm
Many people feel that it’s fine to take a few stalks now and then during the course of the summer and fall, especially if the leaves on them are going to be overshading something else in the garden that needs the sun to be productive. These occasional stalks can be washed, chopped, and frozen in the freezer until enough have accumulated to do something with.
Don’t allow flower stalks to form, as that will weaken next year’s crop. Remove them and discard; don’t consume.
Rhubarb leaves are highly poisonous (see Nutrition below.) Even so, it is safe to compost the leaves:
“While the rhubarb leaves do contain poisonous materials, they can be used in the compost pile. Oxalic acid and soluble oxalates are not readily absorbed by the roots of plants. Compost containing decomposed rhubarb leaves can be safely worked into the soil of vegetable gardens.” Iowa State Extension Service. Safety Concerns about Rhubarb. May 2, 1997. Accessed May 2016 at .http://www.ipm.iastate.edu/ipm/hortnews/1997/5-2-1997/rhubarbsafe.html
Rhubarb stalks don’t become poisonous, even as they age. Iowa State Extension Service says:
“Do the rhubarb stalks become poisonous by summer? … The rhubarb stalks may become somewhat woody by mid-summer, but they don’t become poisonous.” Ibid.
pH values of rhubarb
Rhubarb, California, stewed 3.20 – 3.34
Rhubarb 3.10 – 3.40
Rhubarb, Canned 3.40
Source: FDA. Approximate pH of Foods and Food Products. April 2007. Accessed March 2015.
Once again, the leaves are poisonous. Discard them completely. (It is safe to add the leaves to compost heaps, though, as the poison will break down when decomposed.)
Wash the stalks, rubbing with your finger where any dirt has adhered. Trim off the ends. If it is very stringy, pull out the strings. Cut stalk into pieces anywhere from 2.5 to 5 cm (1 to 2 inches), and use as per your recipe.
Because rhubarb is so acidic, don’t cook in an aluminum pot.
Raw rhubarb contains a lot of water in it; generally, you don’t need to add any when cooking it. Just tightly cover the pot you are cooking it in over a low heat until it releases all its juices, then you can raise the heat a bit, remove the lid and cook a while longer.
In a pressure cooker, put in steamer basket over 250 ml (1 cup / 8 oz) of water and cook on low pressure for 4 minutes. After cooking, scoop it out of the basket into a bowl and stir your sweetener in to taste.
Sweetening the rhubarb
If you can weigh the rhubarb, you will likely need to add sugar to the pot equalling at least 1/4 of the weight of the Rhubarb you are cooking up.
The food writer, Sophie Grigson, says that adding a few sprigs of Sweet Cicely herb can reduce the tartness of the rhubarb and thus reduce the amount of sugar required. Grigson, Sophie. My resistance to rhubarb crumbles. London: The Independent. 19 February 1994.
For sugar-reduced diets, you could use a few drops of liquid stevia or some Splenda® (aka sucralose.)
If your rhubarb is the red stalk variety, if desired you could stir a few drops of red food colouring to it after cooking to deepen the colour.
Try other tart fruit such as cranberries or quince.
Rhubarb leaves are seriously poisonous because they contain very high amounts of Oxalic Acid. Always discard the leaves.
Rhubarb is high in vitamin C and dietary fibre.
A standard 9 inch (23 cm) rhubarb pie recipe will call for 4 cups (500 g / 1 lb / 4 large stalks / 8 small stalks) of rhubarb that has been trimmed of leaves and rough ends and chopped into 1 inch (3 cm) pieces.
550 g / 1 1/4 lbs rhubarb stalks, no leaves but untrimmed = 500 g / 1 lb with rough ends trimmed away
500 g / 1 pound rhubarb stalks (leaves and rough ends trimmed away) = 4 large or 8 small stalks = 4 cups trimmed (1 US quart) chopped into 3 cm (1 inch) pieces = 2 cups cut and cooked
1 small to medium stalk of rhubarb (about 3 cm / 1 inch wide), cut into 3 cm (1 inch) pieces = approximately 1/2 cup ( a good handful) = 2 tablespoons pure rhubarb cooked purée, with no sugar or liquid added
Refrigerate fresh rhubarb stalks wrapped in plastic or in a plastic bag for up to 5 days. Remove (and discard) their leaves first so that the leaves don’t draw moisture from the stalks.
Rhubarb can be home-canned, either on its own, or as part of various preserves, from pie fillings to chutneys. For options, see “Canning rhubarb” on our sister site for home canning.
Rhubarb can also be dehydrated, then stored as is, or ground into powder for use as a spice.
To freeze rhubarb, wash it, chop into 2 to 5 cm (1 to 2 inch) pieces, toss in freezer bag, and freeze for up to a year. Optionally, you may also blanch for 1 minute first (and drain) before freezing. You may also pack in a sugar syrup. For full details, see “Freezing Rhubarb” on the site for the National Center for Home Food Preservation.
The Chinese were growing rhubarb in 3000 BC for what they thought were its medicinal properties in treating headaches and fevers. It was brought to Europe and cultivated there for its purgative abilities. The English first tried using it as food, rather than medicine, in the 1600s. Unfortunately, the brave pioneers of the kitchen focussed on cooking and eating the leaves, which didn’t do anything to popularize the plant as a staple in the kitchen.
Rhubarb appeared in America sometime after the revolution, again, being raised for medicinal properties.
No one seems to have even thought of eating the stalks until the 1800s. You need copious amounts of sweetener to make something from the tart stems, and sugar had been a very expensive commodity up until then (they had honey of course, but honey wasn’t much cheaper.) The Victorians really got the hang of cooking with rhubarb, and valued it as an early-season “fruit” that was available when nothing else had even really started to grow yet.
But even in the first bit of the 1900s, for some reason we just hadn’t fully given up on the leaves. During WW1, the English were encouraged to eat rhubarb leaves as a supplement to fresh vegetables, which added a few home front casualties to the overall toll of the war. ”Consumption of rhubarb leaves as a food substitute for spinach was encouraged in England during World War I until several deaths were attributed to the ingestion of cooked leaves.” Barceloux, Donald G. Rhubarb and Oxalosis (Rheum Species). Mosby, Inc: St. Louis, Missouri. In: Leikin, Jerrold B., Ed. Disease-A-Month.Volume 55, Issue 6, June 2009, Pages 403-411. Robb HF. Death from rhubarb leaves due to oxalic acid poisoning. JAMA 1919; 73:627-62.
Literature & Lore
Native to the south-east part of Russia, beyond the Volga. Thus its name from the ancient Greek: “Rha” (Volga) and “barbarians.”
In some parts of North America, rhubarb is called “the pie plant.”
The North Dakota State University Extension Service once fielded this question about rhubarb and weed killer:
Q: My husband got spray happy, so in the process of spraying cocklebur he sprayed my rhubarb patch. He assures me you can’t kill rhubarb. For his sake lets hope not! He used Trimec. The rhubarb is curled but still green. We have had a great deal of rain. (Ellendale, N.D.)
A: Let me count the ways that husbands can place themselves on thin ice. This certainly has to rank right up there among the top 10. The rain will help. Your husband is wrong, rhubarb can be killed especially with a Trimec product. Tell him to not be so trigger happy next time.  Ron Smith, Horticulturist, NDSU Extension Service. Questions on rhubarb. Accessed June 2016 at .http://www.ext.nodak.edu/extnews/hortiscope/fruitveg/rhubarb.htm
Lois Hole, former Lieutenant Governor of the Canadian province of Alberta, reminisced about the rhubarb she knew while growing up in a small town in the neighboring province of Saskatchewan:
“Rhubarb grew like a weed on the streets and in the backyards of Buchanan, the small Saskatchewan town where I grew up. Far from a nuisance, the tall crimson stalks hidden beneath those large, bristly leaves were the “Red Gold’ of the Prairies. In a climate where hardiness was the ultimate garden virtue, rhubarb’s tenacity made it an indispensable staple, one depended on by generations of prairie families. Fruit choices at the local grocery store were limited back then, making rhubarb’s early emergence and strong flavour all the more welcome. Since there weren’t many fruits to work with, we found a number of ways to enjoy rhubarb.” — Hole, Lois. Introduction to: Rhubarb, more than just pies. Vitt, Sandi and Michael Hickman. Edmonton, Alberta: University of Alberta Press. 2000.
Early documentation of rhubarb leaves poisoning
From: Robb HF. Death from rhubarb leaves due to oxalic acid poisoning. JAMA 1919; 73:627-62.
DEATH FROM RHUBARB LEAVES DUE TO OXALIC ACID POISONING
To the Editor: I enclose herewith a case history reported by Dr. Harry J. Robb of Broadview, Montana. I should be interested in having your opinion on Dr. Robb’s diagnosis of this case. John J. Sippy, M.D., State Epidemiologist, Helena, Montana.
“On the morning of May 6, Mrs. A. made breakfast, but at the time did not feel well. She then went to bed where she remained. She began to have cramplike pains in the abdomen during the forenoon. These pains continued intermittently all day until 12:30 a. m., May 7. I was called to see her, and arrived at her home, 20 miles away, at 1:30 a. m., May 7. At that time she was very weak and pale, and so drowsy that it was difficult for her to answer any questions intelligently.
Her temperature was normal. The respirations were 36 a minute. The radial pulse could not be felt. The heart beat was 120 a minute, The extremities were cold. She could keep nothing in her stomach, and vomited a brown, bloody fluid. I found the complete products of conception of about six weeks’ development, discharged into the bed. The placenta was bloodless, and a small amount of blood discharged with it did not coagulate after several hours.
Heat to the body and stimulants gave no improvement, and her condition continued to become worse until her death, a few hours later. After death there was considerable bleeding from the nose. This blood failed to coagulate.
I learned from Mr. A. that she had not taken any drugs except a couple of acetylsalicylic acid tablets, which she took that day for her pain.
May 5, Mrs. A. prepared some rhubarb for supper. The leaves were fried for greens and the stalks were boiled. She ate most of the leaves herself and seemed to relish them, Mr. A. took a spoonful of the leaves, but preferred the stalks.
Mr. A. said he felt weak and sometimes dizzy, May 6. Mrs. A. had been in good health previous to this illness.
The leaves and root of the-rhubarb plant have a content of oxalic acid in the form of oxalates, the dried roots containing as high as 40 per cent. What the content in the leaves is, I do not know. The marked exhaustion, the vomiting of bloody material, early cardiac failure, the early termination of illness in death, and especially the absence of coagulation of the blood in the case of a person who had been perfectly well apparently, thirty hours previous to death, led to my conclusion that death was due to poisoning from the oxalic acid contained in the leaves of the rhubarb eaten.
I shall gladly answer any additional questions you may wish to ask, and would appreciate very much to hear your decision in the case.” — H. F, Robb, M.D.
Comment.—It seems probable that the case reported by Dr. Robb is one of oxalic acid poisoning as a result of ingesting a relatively large amount of rhubarb leaves. Both the leaves and stalks of rhubarb contain salts of oxalic acid, but the amount is greater in the leaves. A number of deaths from the use of the leaves have been reported; as far back as seventy-five years ago its toxic effects were noted. During the war the use of the leaves as a food substitute was encouraged in England; when the danger of fatal poisoning became apparent (owing to several deaths), warnings were issued against the use of the leaves. The small quantities of oxalates which occur in the stalks are seemingly ineffective in the quantities ordinarily eaten. Oxalic acid and the oxalates produce local irritation and corrosion ; “in addition they produce violent stimulation and later paralysis by depriving the tissues, of their calcium through precipitation” (Sollmann, Pharmacology, 1917, p. 691). The symptoms are usually those of collapse, possibly preceded by convulsions. The nephritis produced by oxalic acid was discussed editorially in The Journal, June 16, 1917, p. 1820. The chemical antidote would be the administration of calcium.—Ed.
The following references may be consulted:
Oxalic Acid in Foods, editorial, The Journal, Nov. 17, 1917, p. 1699.
Poisoning from Rhubarb Leaves, The Journal, June 30, 1917, p. 1954.
Death from Eating Rhubarb Leaves, London Letter, The Journal, June 23, 1917, p. 1978.
Maillart: Poisoning from Rhubarb Leaves, Rev. Méd. de la Suisse Rom., June, 1917.
Poisoning by Rhubarb Leaves, Lancet, 1: 847, 1917.
Rhubarb Poisoning by Leaves, Pharm. J. 98:413, 1917.
M. L. J.: Severe Poisoning Apparently Due to Eating Rhubarb, Lancet 1:1110, 1915.
Fry, H. J. B.: The Decalcifying Action of Oxalic Acid Illustrated by Three Cases of Poisoning, Lancet 2:220, 1913.
Brown, O. H., and Scott, W. G.: Oxalic Acid Poisoning, The Journal, April 27, 1912, p. 1280
Adams, Stephen. Delia Smith causes rhubarb shortage. London: Daily Telegraph. 4 April 2010.
|↑1||Jauraon, Richard. Answers to Frequently Asked Rhubarb Questions. Iowa State University Extension. 14 May 2004. Accessed June 2016 at .http://www.ipm.iastate.edu/ipm/hortnews/2004/5-14-2004/rhubarb.html|
|↑2||Rhubarb – Stewed. United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2009. Page 2-22.|
|↑3||Wolford, Ron. University of Illinois Extension. Watch your garden grow: rhubarb. Accessed June 2016 at .https://extension.illinois.edu/veggies/rhubarb.cfm|
|↑4||Iowa State Extension Service. Safety Concerns about Rhubarb. May 2, 1997. Accessed May 2016 at .http://www.ipm.iastate.edu/ipm/hortnews/1997/5-2-1997/rhubarbsafe.html|
|↑6||Grigson, Sophie. My resistance to rhubarb crumbles. London: The Independent. 19 February 1994.|
|↑7||”Consumption of rhubarb leaves as a food substitute for spinach was encouraged in England during World War I until several deaths were attributed to the ingestion of cooked leaves.” Barceloux, Donald G. Rhubarb and Oxalosis (Rheum Species). Mosby, Inc: St. Louis, Missouri. In: Leikin, Jerrold B., Ed. Disease-A-Month.Volume 55, Issue 6, June 2009, Pages 403-411.|
|↑8||Robb HF. Death from rhubarb leaves due to oxalic acid poisoning. JAMA 1919; 73:627-62.|
|↑9||Ron Smith, Horticulturist, NDSU Extension Service. Questions on rhubarb. Accessed June 2016 at .http://www.ext.nodak.edu/extnews/hortiscope/fruitveg/rhubarb.htm|