Rhubarb
Rhubarb is a
perennial plant that grows from thick short
rhizomes, comprising the genus
Rheum. The large, somewhat triangular
leaf blades are elevated on long, fleshy
petioles. The
flowers are small, greenish-white, and borne in large compound leafy
inflorescences.
The plant is indigenous to
Asia, and many suggest that it was often used by the
Mongolians; particularly, the
Tatars tribes of the Gobi. Varieties of rhubarb have a long history as medicinal plants in
Traditional Chinese Medicine, but the use of rhubarb as food is a relatively recent innovation, first recorded in
17th century England, after affordable
sugar became available to common people.
Rhubarb is now grown in many areas, primarily for its fleshy petioles, commonly known as
rhubarb sticks. In temperate climate rhubarb is one of the first food plants to be ready for harvest, usually in April/May. The
petioles can be cooked in a variety of ways. Stewed, they yield a tart sauce that can be eaten with sugar or used as filling for
pies,
tarts, and
crumbles. This common use led to the slang term for rhubarb,
"pie plant" (
piestengel in
German). Cooked with
strawberries as a sweetener, rhubarb makes excellent jam. It can also used to make
wine.
In former days, a common and affordable sweet for children in parts of the United Kingdom was a tender stick of rhubarb, dipped in
sugar. In the
UK the first rhubarb of the year is grown by candlelight in dark sheds dotted around the noted‘
Rhubarb Triangle' of
Wakefield,
Leeds and
Morley.
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A Homemade Rhubarb Pie |
In warm climates, rhubarb will grow all year round, but in colder climates the parts of the plant above the ground disappear completely during winter, and begin to grow again from the root in early spring. It can be
forced, that is, encouraged to grow early, by raising the local temperature. This is commonly done by placing an upturned bucket over the shoots as they come up.
The plant is represented by about 60 extant species.
Those most commonly used in cooking are the
Garden Rhubarb (
R. rhabarbarum) and
R. rhaponticum, which though a true rhubarb bears the common name False Rhubarb. The drug rheum is prepared from the rhizomes and
roots of another species,
R. officinale or Medicinal Rhubarb. This species is also native to Asia, as is the
Turkey Rhubarb (
R. palmatum). Another species, the
Sikkim Rhubarb (
R. nobile), is limited to the
Himalaya.
Rhubarb is used as a strong
laxative and for its astringent effect on the
mucous membranes of the mouth and the
nasal cavity.
Rheum species have been recorded as
larval food plants for some
Lepidoptera species including
Brown-tail,
Buff Ermine,
Cabbage Moth,
Large Yellow Underwing,
The Nutmeg,
Setaceous Hebrew Character and
Turnip Moth.
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Rhubarb |
Rhubarb leaves contain
poisonous substances. Rhubarb leaf poisoning is most often caused by
oxalic acid, a
corrosive and
nephrotoxic acid that is abundantly present in a lot of plants. The
LD50 for pure oxalic acid is predicted to be about 375
mg/
kg body weight, or about 25
g for a 65 kg human. While the oxalic acid content of rhubarb leaves can vary, it averages about 0.5%, so a rather unlikely five kilograms of the extremely sour leaves would have to be consumed to reach an LD50 dose. In the petioles, the amount of oxalic acid is much lower, especially when harvested before mid-June so the
phloem will explode (on the northern hemisphere), but it is still enough to cause slightly rough teeth.
The roots and stems are rich in
anthraquinones, such as
emodin and
rhein. These substances are cathartic and
laxative, which explains the sporadic abuse of Rhubarb as a
slimming agent. Anthraquinones are yellow or orange and may colour the
urine.
It is or was common for a crowd of
extras in
acting to shout the word "rhubarb" repeatedly and out of step with each other, to cause the effect of general hubbub. As a result, the word "rhubarb" sometimes is used to mean "length of superfluous text in speaking or writing", or a general term to refer to irrelevant chatter by chorus or extra actors.
Possibly from this usage, possibly from a variant on "
rube", or perhaps some of both, the word also denotes a loud argument. The term has been most commonly used in
baseball.
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The Rhubarb Compendium
