Rhubarb

Rhubarb

Overview
Rhubarb is a group of plants that belong to the genus Rheum
Rheum (genus)
Rheum is a genus of about 60 perennial plants in the family Polygonaceae. The genus includes the vegetable rhubarb The species have large somewhat triangular shaped leaves with long, fleshy petioles. The flowers are small, greenish-white to rose-red, and grouped in large compound leafy...

in the family Polygonaceae
Polygonaceae
Polygonaceae is a family of flowering plants known informally as the "knotweed family" or "smartweed family"— "buckwheat family" in the United States. The name is based on the genus Polygonum and was first used by Antoine Laurent de Jussieu in 1789 in his book, Genera Plantarum. The name refers...

. They are herbaceous perennial plant
Perennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...

s growing from short, thick rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...

s. They have large leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 that are somewhat triangular-shaped with long fleshy petiole
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...

s. They have small flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s grouped in large compound leafy greenish-white to rose-red
Rose (color)
Rose is the color halfway between red and magenta on the HSV color wheel, also known as the RGB color wheel, on which it is at hue angle of 330 degrees.Rose is one of the tertiary colors on the HSV color wheel...

 inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...

s.

Although the leaves are toxic, various parts of the plants have medicinal and culinary uses. The traditional Chinese pharmacopeia features rhubarb (as a laxative).
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Unanswered Questions
Encyclopedia
Rhubarb is a group of plants that belong to the genus Rheum
Rheum (genus)
Rheum is a genus of about 60 perennial plants in the family Polygonaceae. The genus includes the vegetable rhubarb The species have large somewhat triangular shaped leaves with long, fleshy petioles. The flowers are small, greenish-white to rose-red, and grouped in large compound leafy...

in the family Polygonaceae
Polygonaceae
Polygonaceae is a family of flowering plants known informally as the "knotweed family" or "smartweed family"— "buckwheat family" in the United States. The name is based on the genus Polygonum and was first used by Antoine Laurent de Jussieu in 1789 in his book, Genera Plantarum. The name refers...

. They are herbaceous perennial plant
Perennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...

s growing from short, thick rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...

s. They have large leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 that are somewhat triangular-shaped with long fleshy petiole
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...

s. They have small flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s grouped in large compound leafy greenish-white to rose-red
Rose (color)
Rose is the color halfway between red and magenta on the HSV color wheel, also known as the RGB color wheel, on which it is at hue angle of 330 degrees.Rose is one of the tertiary colors on the HSV color wheel...

 inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...

s.

Although the leaves are toxic, various parts of the plants have medicinal and culinary uses. The traditional Chinese pharmacopeia features rhubarb (as a laxative). In culinary use, fresh raw stalks are crisp (similar to celery) with a strong tart taste; most commonly the plant's stalks are cooked and used in pies and other foods for their tart flavour. A number of varieties have been domesticated for human consumption, most of which are recognised as Rheum x hybridum by the Royal Horticultural Society
Royal Horticultural Society
The Royal Horticultural Society was founded in 1804 in London, England as the Horticultural Society of London, and gained its present name in a Royal Charter granted in 1861 by Prince Albert...

.

Rhubarb is usually considered to be a vegetable
Vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....

; however, in the United States, a New York court decided in 1947 that since it was used in the United States as a fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

, it was to be counted as a fruit for the purposes of regulations and duties. A side effect was a reduction in taxes paid.

Cultivation



Rhubarb is now grown in many areas and, thanks to greenhouse production, is available throughout much of the year. Rhubarb grown in hothouses (heated greenhouse
Greenhouse
A greenhouse is a building in which plants are grown. These structures range in size from small sheds to very large buildings...

s) 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, more tender and sweeter-tasting than cultivated rhubarb. In temperate climates, rhubarb is one of the first food plants to be ready for harvest
Harvest
Harvest is the process of gathering mature crops from the fields. Reaping is the cutting of grain or pulse for harvest, typically using a scythe, sickle, or reaper...

, usually in mid- to late spring (April/May in the northern hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

, October/November in the southern hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

), and the season for field-grown plants lasts until September. In the northwestern US states of Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

 and Washington, there are typically two harvests: one from late April to May and another from late June into July. Rhubarb is ready to be consumed as soon as it is harvested, and freshly cut stalks will be firm and glossy.

In the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, the first rhubarb of the year is harvested by candlelight in forcing sheds - where all other light is excluded; the sheds are dotted around the noted "Rhubarb Triangle
Rhubarb Triangle
The Rhubarb Triangle is a triangle in West Yorkshire, England located between Wakefield, Morley and Rothwell famous for producing early forced rhubarb. It includes Kirkhamgate, East Ardsley, Stanley, Lofthouse and Carlton. The Rhubarb Triangle was originally much bigger covering an area between...

" of Wakefield
Wakefield
Wakefield is the main settlement and administrative centre of the City of Wakefield, a metropolitan district of West Yorkshire, England. Located by the River Calder on the eastern edge of the Pennines, the urban area is and had a population of 76,886 in 2001....

, Leeds
Leeds
Leeds is a city and metropolitan borough in West Yorkshire, England. In 2001 Leeds' main urban subdivision had a population of 443,247, while the entire city has a population of 798,800 , making it the 30th-most populous city in the European Union.Leeds is the cultural, financial and commercial...

, and Morley
Morley, West Yorkshire
Morley is a market town and civil parish within the metropolitan borough of the City of Leeds, in West Yorkshire, England. It lies approximately south-west of Leeds city centre. Together with Drighlington, Gildersome, Churwell, Tingley and East/West Ardsley, the town had a population of 47,579 in...

, a practice that produces a sweeter, more tender stalk.

Rhubarb will grow year-round in warm climates, but in temperate climates, the aboveground portion of the plant completely withers away at the onset of freezing temperature; the plant grows from the root at the return of warm weather. Rhubarb growth can be forced or encouraged to grow early by raising the local temperature, usually by placing an upturned bucket over the new shoots. Because rhubarb is a seasonal plant, obtaining fresh rhubarb out of season is difficult in colder climates, such as in the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

.

Rhubarb can successfully be planted in containers, so long as the container is large enough to accommodate a season's growth.

The colour of rhubarb stalks can vary from the commonly associated crimson red, through speckled light pink
Variations of pink
This article is about notable tints and shades of the color pink. These various colors are shown below.-Pink:At right is displayed web color pink.This color is identical to the color Tamarisk, the color of the flowers of the Tamarisk plant....

, to simply light green. Rhubarb stalks are poetically described as crimson stalks. The colour results from the presence of anthocyanin
Anthocyanin
Anthocyanins are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH...

s, and varies according to both rhubarb variety and production technique. The colour is not related to its suitability for cooking: The green-stalked rhubarb is more robust and has a higher yield, but the red-coloured stalks are much more popular with consumers.

Historical cultivation



Rhubarb has been used for medical purposes by the Chinese for thousands of years and appears in The Divine Farmer's Herb-Root Classic which legend attributes to the mythical Shen Nung, the Yan Emperor
Yan Emperor
The Yan Emperor, or Yandi was a legendary Han Chinese ruler who lived in pre-dynastic China. Modern scholarship has identified the Sheep's Head Mountains just north of Gaoping in Shanxi Province as his homeland and territory....

, but is thought to have been compiled about 2700 years ago. Though Dioscurides' description of ρηον or ρά, a root brought to Greece from beyond the Bosphorus may have included rhubarb, the commerce did not become securely established until Islamic times, when it was imported along the Silk Road
Silk Road
The Silk Road or Silk Route refers to a historical network of interlinking trade routes across the Afro-Eurasian landmass that connected East, South, and Western Asia with the Mediterranean and European world, as well as parts of North and East Africa...

 reaching Europe from the 14th century through the ports of Aleppo
Aleppo
Aleppo is the largest city in Syria and the capital of Aleppo Governorate, the most populous Syrian governorate. With an official population of 2,301,570 , expanding to over 2.5 million in the metropolitan area, it is also one of the largest cities in the Levant...

 and Smyrna
Smyrna
Smyrna was an ancient city located at a central and strategic point on the Aegean coast of Anatolia. Thanks to its advantageous port conditions, its ease of defence and its good inland connections, Smyrna rose to prominence. The ancient city is located at two sites within modern İzmir, Turkey...

, and becoming known as "Turkish rhubarb". Later, when the usual route lay through Russia, "Russian rhubarb" became the familiar term.

For centuries the plant has grown wild along the banks of the River Volga, for which the ancient Scythian hydronym
Hydronym
A hydronym is a proper name of a body of water. Hydronymy is the study of hydronyms and of how bodies of water receive their names and how they are transmitted through history...

 was Rhā. The expense of transportation across Asia caused rhubarb to be highly expensive in medieval Europe where it was several times the price of other valuable herbs and spices such as cinnamon
Cinnamon
Cinnamon is a spice obtained from the inner bark of several trees from the genus Cinnamomum that is used in both sweet and savoury foods...

, opium
Opium
Opium is the dried latex obtained from the opium poppy . Opium contains up to 12% morphine, an alkaloid, which is frequently processed chemically to produce heroin for the illegal drug trade. The latex also includes codeine and non-narcotic alkaloids such as papaverine, thebaine and noscapine...

 and saffron
Saffron
Saffron is a spice derived from the flower of Crocus sativus, commonly known as the saffron crocus. Crocus is a genus in the family Iridaceae. Each saffron crocus grows to and bears up to four flowers, each with three vivid crimson stigmas, which are each the distal end of a carpel...

. The merchant explorer Marco Polo
Marco Polo
Marco Polo was a Venetian merchant traveler from the Venetian Republic whose travels are recorded in Il Milione, a book which did much to introduce Europeans to Central Asia and China. He learned about trading whilst his father and uncle, Niccolò and Maffeo, travelled through Asia and apparently...

 was therefore much interested to find the plant being grown and harvested in the mountains of Tangut province. A measure of the value set upon rhubarb can be gotten from Ruy Gonzáles de Clavijo
Ruy Gonzáles de Clavijo
Ruy González de Clavijo was a Castilian traveller and writer. In 1403-05 Clavijo was the ambassador of Henry III of Castile to the court of Timur, founder and ruler of the Timurid Empire...

's report of his embassy in 1403-05 to Timur
Timur
Timur , historically known as Tamerlane in English , was a 14th-century conqueror of West, South and Central Asia, and the founder of the Timurid dynasty in Central Asia, and great-great-grandfather of Babur, the founder of the Mughal Dynasty, which survived as the Mughal Empire in India until...

 in Samarkand
Samarkand
Although a Persian-speaking region, it was not united politically with Iran most of the times between the disintegration of the Seleucid Empire and the Arab conquest . In the 6th century it was within the domain of the Turkic kingdom of the Göktürks.At the start of the 8th century Samarkand came...

: "The best of all merchandise coming to Samarkand was from China: especially silks, satins, musk, rubies, diamonds, pearls, and rhubarb...".

The term rhubarb is a combination of the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 rha and barbarum; rha is a term that refers both to the plant and to the River Volga. Rhubarb first came to the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 in the 1820s, entering the country in Maine
Maine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...

 and Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...

 and moving westwards with the European American
European American
A European American is a citizen or resident of the United States who has origins in any of the original peoples of Europe...

 settlers.

Uses


Rhubarb is grown primarily for its fleshy petioles
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...

, commonly known as rhubarb sticks or stalks. The use of rhubarb stems as food is a relatively recent innovation, first recorded in 17th century England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, after affordable sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

 became available to common people, and reaching a peak between the 20th century's two world war
World war
A world war is a war affecting the majority of the world's most powerful and populous nations. World wars span multiple countries on multiple continents, with battles fought in multiple theaters....

s.

Rhubarb can be dehydrated and infused with fruit juice. In most cases it is infused with strawberry juice to mimic the popular strawberry rhubarb pie
Strawberry rhubarb pie
A Strawberry rhubarb pie , is a type of tart/sweet pie made with a strawberry and rhubarb filling, and sometimes containing tapioca. It has a bottom pie crust and often a lattice-style upper crust....

.

Rhubarb root produces a rich brown dye similar to walnut husks. It is used in northern regions where walnut trees do not survive.

Cooking



One way is to cut up the stalks into 1 inches (2.5 cm) pieces and stew them (boil in water); it is necessary only to barely cover the stalks with water because rhubarb stalks contain a great deal of water; add 1/2 to 3/4 cup of sugar for each pound of rhubarb; then add cinnamon
Cinnamon
Cinnamon is a spice obtained from the inner bark of several trees from the genus Cinnamomum that is used in both sweet and savoury foods...

 and/or nutmeg
Nutmeg
The nutmeg tree is any of several species of trees in genus Myristica. The most important commercial species is Myristica fragrans, an evergreen tree indigenous to the Banda Islands in the Moluccas of Indonesia...

 to taste. Sometimes a tablespoon of lime juice or lemon juice
Lemon juice
The lemon fruit, from a citrus plant, provides a useful liquid when squeezed. Lemon juice, either in natural strength or concentrated, is sold as a bottled product, usually with the addition of preservatives and a small amount of lemon oil.-Uses:...

 is added. The sliced stalks are boiled until soft. An alternative method is to simmer slowly without adding water, letting the rhubarb cook in its own juice.

At this stage, cooked with strawberries or apples as a sweetener, or with stem or root ginger
Ginger
Ginger is the rhizome of the plant Zingiber officinale, consumed as a delicacy, medicine, or spice. It lends its name to its genus and family . Other notable members of this plant family are turmeric, cardamom, and galangal....

, rhubarb makes excellent jam. Other fruits, with the addition of pectin
Pectin
Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot...

 (or using sugar with pectin already added), can be added to rhubarb at this stage to make a variety of jams: the fruit is added at a ratio of one part rhubarb to two parts fruit, consisting of strawberries, raspberries, or chopped plums, apricots, or apples. Boiling should continue for at least ten minutes after all fruit is completely softened, depending on whether a simple refrigerated jam is made, or if (with longer cooking) jam is to be bottled for a long shelf life.
To make a "sauce" of rhubarb (to which dried fruit could be added near the end), continue simmering 45 minutes to one hour at medium heat, until the sauce is mostly smooth and the remaining discrete stalks can easily be pierced with a fork, yielding a smooth tart-sweet sauce with a flavor similar to sweet and sour sauce. This sauce is called rhubarb sauce, analogous to apple sauce. Another name for it is stewed rhubarb. Like apple sauce, this sauce is usually stored in the refrigerator
Refrigerator
A refrigerator is a common household appliance that consists of a thermally insulated compartment and a heat pump that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room...

 and eaten cold. The sauce, when stewed over medium heat only a short time (about 20 minutes) and with only a little water so that the rhubarb stalks stay mostly discrete, may be used as filling for pie
Pie
A pie is a baked dish which is usually made of a pastry dough casing that covers or completely contains a filling of various sweet or savoury ingredients....

s (see rhubarb pie
Rhubarb pie
Rhubarb pie is a pie which is particularly popular in those areas where the rhubarb plant is commonly cultivated, including Sweden, the United Kingdom, Ireland and the New England and Upper Midwestern regions of the United States. Besides diced rhubarb, it almost always contains a large amount of...

), tart
Tart
A tart is a baked dish consisting of a filling over a pastry base with an open top not covered with pastry. The pastry is usually shortcrust pastry; the filling may be sweet or savoury, though modern tarts are usually fruit-based, sometimes with custard....

s, and crumble
Crumble
A crumble is a dish of British and Irish origin that can be made in a sweet or savoury version, depending on ingredients used, although the sweet version is much more common. It also can be traced to American cuisine during the European colonization of the Americas. A sweet variety usually contains...

s. Sometimes stewed strawberries
Strawberry
Fragaria is a genus of flowering plants in the rose family, Rosaceae, commonly known as strawberries for their edible fruits. Although it is commonly thought that strawberries get their name from straw being used as a mulch in cultivating the plants, the etymology of the word is uncertain. There...

 are mixed with the rhubarb to make strawberry-rhubarb pie. This common use has led to the slang term for rhubarb, "pie plant", by which name it was more commonly known in the United States in the latter nineteenth century. In her novella The First Four Years
The First Four Years (novel)
The First Four Years is a book written by Laura Ingalls Wilder and found in the belongings of Rose Wilder Lane by Roger Lea MacBride, Rose's heir, upon Rose's death in 1968...

, American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 author Laura Ingalls Wilder
Laura Ingalls Wilder
Laura Elizabeth Ingalls Wilder was an American author who wrote the Little House series of books based on her childhood in a pioneer family...

 refers to rhubarb as "pie plant". It can also be used to make a fruit wine
Fruit wine
Fruit wines are fermented alcoholic beverages made from a variety of base ingredients ; they may also have additional flavours taken from fruits, flowers, and herbs. This definition is sometimes broadened to include any fermented alcoholic beverage except beer...

.

In former days, a common and affordable sweet for children in parts of the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 and Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 was a tender stick of rhubarb, dipped in sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

. It is still eaten this way in western Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

 and Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

 and some other parts of the world, including rural Eastern Ontario
Eastern Ontario
Eastern Ontario is a subregion of Southern Ontario in the Canadian province of Ontario which lies in a wedge-shaped area between the Ottawa River and St. Lawrence River...

. In Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

, Chilean rhubarb is sold on the street with salt or dried pepper, not sugar.

Medicine


Rhubarb can be used as a strong laxative
Laxative
Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under...

. Its roots have been used as a laxative for at least 5,000 years.

The roots and stems are rich in anthraquinone
Anthraquinone
Anthraquinone, also called anthracenedione or dioxoanthracene is an aromatic organic compound with formula . Several isomers are possible, each of which can be viewed as a quinone derivative...

s, such as emodin
Emodin
Emodin is a purgative resin, 6-methyl-1,3,8-trihydroxyanthraquinone, from rhubarb, the buckthorn and Japanese Knotweed...

 and rhein
Rhein (molecule)
Rhein, also known as cassic acid, is a substance in the anthraquinone group found in rhubarb species like Rheum undulatum or Rheum palmatum or in Cassia reticulata. Rhein has been reevaluated as a new antibacterial agent against Staphylococcus aureus in 2008....

. These substances are cathartic
Cathartic
In medicine, a cathartic is a substance that accelerates defecation. This is in contrast to a laxative, which is a substance which eases defecation, usually by softening feces. It is possible for a substance to be both a laxative and a cathartic...

 and laxative, which explains the sporadic use of rhubarb as a dieting
Dieting
Dieting is the practice of eating food in a regulated fashion to achieve or maintain a controlled weight. In most cases dieting is used in combination with physical exercise to lose weight in those who are overweight or obese. Some athletes, however, follow a diet to gain weight...

 aid.

Rhubarb roots are used in traditional Chinese medicine
Traditional Chinese medicine
Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...

; rhubarb also appears in medieval Arabic and European prescriptions.

The rhizomes ('roots') contain stilbenoid compounds (including rhaponticin
Rhaponticin
Rhaponticin is a stilbene glucoside compound that can be found in rhubarb rhizomes.It has beneficial effects on diabetic mice, and may be relevant to Alzheimers disease....

) which seem to lower blood glucose levels in diabetic mice.

Toxicity



Rhubarb leaves contain poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

ous substances, including oxalic acid
Oxalic acid
Oxalic acid is an organic compound with the formula H2C2O4. This colourless solid is a dicarboxylic acid. In terms of acid strength, it is about 3,000 times stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations...

 which is a nephrotoxic and corrosive
Corrosive
A corrosive substance is one that will destroy or irreversibly damage another surface or substance with which it comes into contact. The main hazards to people include damage to the eyes, the skin, and the tissue under the skin; inhalation or ingestion of a corrosive substance can damage the...

 acid that is present in many plants. The (median lethal dose) for pure oxalic acid in rats is about 375 mg/kg body weight
Body weight
The term body weight is used in daily English speech as well as in the contexts of biological and medical sciences to describe the mass of an organism's body. Body weight is measured in kilograms throughout the world, although in some countries it is still measured in pounds or stones and pounds...

, or about 25 gram
Gram
The gram is a metric system unit of mass....

s for a 65 kg (~140 lb) human. (Other sources give a much higher oral LDLo
Lowest published lethal dose
In toxicology, the LDLo is the lowest dosage per unit of bodyweight of a substance known to have resulted in fatality in a particular animal species...

 (lowest published lethal dose) of 600 mg/kg.) While the oxalic acid content of rhubarb leaves can vary, a typical value is about 0.5%, so a rather unlikely 5 kg of the extremely sour leaves would have to be consumed to reach an of oxalic acid. Cooking the leaves with soda can make them more poisonous by producing soluble oxalate
Oxalate
Oxalate , is the dianion with formula C2O42− also written 22−. Either name is often used for derivatives, such as disodium oxalate, 2C2O42−, or an ester of oxalic acid Oxalate (IUPAC: ethanedioate), is the dianion with formula C2O42− also written (COO)22−. Either...

s. However, the leaves are believed to contain also an additional, unidentified toxin, which might be an anthraquinone
Anthraquinone
Anthraquinone, also called anthracenedione or dioxoanthracene is an aromatic organic compound with formula . Several isomers are possible, each of which can be viewed as a quinone derivative...

 glycoside
Glycoside
In chemistry, a glycoside is a molecule in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme...

 (also known as senna glycosides
Senna glycosides
Senna glycosides or sennosides are a number of anthraquinone derivatives useful as a laxative. They are dimeric glycosides named after their abundant occurrence in plants of the genus Senna....

).

In the petioles
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...

, the amount of oxalic acid is much lower, only about 2-2.5% of the total acidity which is dominated by malic acid
Malic acid
Malic acid is an organic compound with the formula HO2CCH2CHOHCO2H. It is a dicarboxylic acid which is made by all living organisms, contributes to the pleasantly sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms , though only the L-isomer exists...

. This means that the raw stalks may not be hazardous, although the tart taste of raw stalks is so strong as to be unpalatable to many.

Pests


The rhubarb curculio, Lixus concavus
Lixus concavus
Lixus concavus , is a member of the weevils group, also called the snout beetles. Rhubarb is a host, together with dock, sunflower and thistle.-Characteristics:...

, is a member of the weevils group, also called the snout beetles. Rhubarb is a host, damage being visible mainly on the leaves and stalks, with gummosis
Gummosis
Gummosis is the formation of patches of a gummy substance on the surface of certain plants, particularly fruit trees. This occurs when sap oozes from wounds or cankers as a reaction to outside stimuli such as adverse weather conditions, infections, insect problems, or mechanical damage. It is...

 and oval or circular feeding and/or egg-laying sites.

Hungry wildlife will dig up and eat rhubarb roots in the spring as stored starches are turned to sugars for new foliage growth.

"Rhubarb rhubarb"



In British theatre and early radio drama, the words "rhubarb rhubarb" were repeated for the effect of unintelligible conversation on the background
This usage lent its title to the 1969 film Rhubarb
Rhubarb (1969 film)
Rhubarb was a 1969 British short film written and directed by Eric Sykes, starring Sykes and Harry Secombe. The dialogue consisted entirely of repetitions of the word "rhubarb", all the characters last names were "Rhubarb", and even the license plates on vehicles were "RHU BAR B"...

and its 1980 remake Rhubarb Rhubarb
Rhubarb Rhubarb
Rhubarb Rhubarb is a 30 minute television comedy special made by Thames TV and transmitted in 1980. The special is a re-make of Eric Sykes' 1969 film, Rhubarb.-Plot:...

.

Further reading


External links