Rhubarbs are several species of large-leaved, perennial, herbaceous plants in the buckwheat family (Polygonaceae). Rhubarbs originated in eastern Asia and were not cultivated in Europe until the nineteenth century. Rhubarbs have been used as medicinal plants, as food, and as garden ornamentals.
The initial uses of rhubarb were medicinal, for which both the medicinal rhubarb (Rheum officinale) and, to a lesser degree, the edible rhubarb (R. rhaponticum) are used. In China, the roots of rhubarb are dried and pulverized, and are used to treat various ailments. Rhubarb is commonly used as a laxative, to treat indigestion, and as a tonic. These were also the first uses of rhubarb in Europe, but later on it was discovered that the petioles, or leafstalks, of the plant are edible and tasty when properly prepared.
The edible part of the rhubarb is the petiole of the leaf, which is usually a bright-red color due to the presence of pigments known as anthocyanins. The actual leaf blade has concentrations of oxalic acid great enough to be considered poisonous, and is not eaten. Large doses of rhubarb leaf can cause convulsions and coma. Rhubarb petioles are extremely bitter because of their large content of organic acids, including oxalic and malic acids. The tartness of these acids can be neutralized by cooking rhubarb with a pinch of baking soda (sodium bicarbonate), and rhubarb is also usually sweetened with sugar or fruit before being eaten. Rhubarb is usually steamed or stewed to prepare it for eating, and it is often baked into pies or used as a component of jam and sauces.
Rhubarbs are commonly planted as an attractive, reddish-colored foliage plant in gardens. Various species are used for this purpose, including the Indian or China rhubarb (R. palmatum).