Rhubarb is a group of plants that belong to the genus Rheum in the family Polygonaceae.
They are herbaceous perennial plants growing from short, thick rhizomes. They have large leaves that are somewhat triangular-shaped with long fleshy petioles. They have small flowers grouped in large compound leafy greenish-white to rose-red inflorescences.
Although the leaves are toxic, various parts of the plants have medicinal uses. 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.
Rhubarb is botanically classified as a vegetable; however, in the United States a New York court decided in 1947 that since it was used in the United States as a fruit it was to be counted as a fruit for the purposes of regulations and duties. A side effect was a reduction in taxes paid.
One way is to cut up the stalks into one-inch pieces and stew them (boil in water); it is only necessary 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 and/or nutmeg to taste. Sometimes a tablespoon of lime juice or lemon juice 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, rhubarb makes excellent jam. Other fruits, with the addition of pectin (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 two parts fruit to one part rhubarb, 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, which yield a smooth tart-sweet sauce with a flavor similar to sweet and sour sauce. This sauce is called rhubarbsauce, analogous to applesauce. Like applesauce, this sauce is usually stored in the refrigerator 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 pies (see rhubarb pie), tarts, and crumbles. Sometimes stewed strawberries 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”, American author Laura Ingalls Wilder refers to rhubarb as “pie plant”. It can also be used to make a fruit wine.
In former days, a common and affordable sweet for children in parts of the United Kingdom and Sweden was a tender stick of rhubarb, dipped in sugar. It is still eaten this way in western Norway and some other parts of the world. In the United Kingdom the first rhubarb of the year is harvested by candlelight in dark sheds dotted around the noted “Rhubarb Triangle” of Wakefield, Leeds, and Morley, a practice that produces a sweeter, more tender stalk.