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The rhizomes of rhubarb are collected from plants eight to ten years old. Then the rhizomes are dried either in the sun or in the ovens. After the drying operation the rhizomes are peeled. Rhubarb was used in China more than 4000 years ago. It was used by the Greek and Roman physicians and was used in Europe in the middle ages.
Rhubarb is used for its purgative action.