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Rhubarb (''Rheum rhabarbarum'') is a species of plant in the family Polygonaceae. It is a herbaceous perennial growing from short, thick rhizomes. It produces large leaves that are somewhat triangular, with long fleshy stalks and small flowers grouped in large compound leafy greenish-white to rose-red inflorescences. In culinary use, fresh raw leaf stalks (petioles) are crisp (similar to celery) with a strong, tart taste. Most commonly, the stalks are cooked with sugar and used in pies and other desserts. A number of varieties have been domesticated for human consumption, most of which are recognised as ''Rheum'' x ''hybridum'' by the Royal Horticultural Society. Rhubarb is usually considered a vegetable. In the United States, however, a New York court decided in 1947 that, since it was used in the United States as a fruit, it counted as a fruit for the purposes of regulations and duties. A side effect was a reduction on imported rhubarb tariffs, as tariffs were higher for vegetables than fruits.〔findlaw.com "(NIX v. HEDDEN, 149 U.S. 304 (1893) )〕 Rhubarb contains anthraquinones including rhein, and emodin and their glycosides (e.g. glucorhein), which impart cathartic and laxative properties. It is hence useful as a cathartic in case of constipation.〔(【引用サイトリンク】title=Pharmacognosy of Rhubarb )〕 ==Cultivation== Rhubarb is grown widely, and with greenhouse production it is available throughout much of the year. Rhubarb grown in hothouses (heated greenhouses) 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 outdoors rhubarb.〔Rombauer, Irma S. ''Joy of Cooking'' Indianapolis/New York:1975 Bobbs-Merrill Co., Inc. Page 142〕 In temperate climates, rhubarb is one of the first food plants harvested, usually in mid- to late spring (April/May in the Northern Hemisphere, October/November in the Southern Hemisphere), and the season for field-grown plants lasts until September. In the northwestern US states of Oregon and Washington, there are typically two harvests, from late April to May and from late June into July. Rhubarb is ready to consume as soon as harvested, and freshly cut stalks are firm and glossy. In the United Kingdom, the first rhubarb of the year is harvested by candlelight in forcing sheds where all other light is excluded – a practice that produces a sweeter, more tender stalk.〔McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. New York, NY: Scribner, 2004. p 367〕 These sheds are dotted around the noted "Rhubarb Triangle" of Wakefield, Leeds, and Morley.〔(【引用サイトリンク】url=http://www.wakefield.gov.uk/CultureAndLeisure/HistoricWakefield/Rhubarb/default.htm )〕 The advocate of organic gardening Lawrence D Hills lists his favorite rhubarb varieties for flavor as Hawke's Champagne, Victoria, Timperley Early, and Early Albert, also recommending Gaskin's Perpetual for having the lowest level of oxalic acid, allowing it to be harvested over a much longer period of the growing season without developing excessive sourness.〔Lawrence D Hills. Organic Gardening. Penguin 1997. page 145〕 Because rhubarb is a seasonal plant, obtaining fresh rhubarb out of season is difficult in colder climates, such as in the UK, Ireland, Russia, etc. Rhubarb thrives in areas of direct sunlight and can successfully be planted in containers if they are large enough to accommodate a season's growth. Rhubarb damaged by severe cold should not be eaten, as it may be high in oxalic acid, which migrates from the leaves and can cause illness.〔 (【引用サイトリンク】publisher=Ohio State University Extension Fact Sheet ) 〕 The color of rhubarb stalks can vary from the commonly associated crimson red, through speckled light pink, to simply light green. Rhubarb stalks are poetically described as "crimson stalks". The color results from the presence of anthocyanins, and varies according to both rhubarb variety and production technique. The color 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rhubarb」の詳細全文を読む スポンサード リンク
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