Rhubarb is a common name used to decribe the plants of the Rheum genus.Often though to be a fruit, rhubarb is actually a vegetable, closely related to the sorrel family.

Originating in the mountains of the North-western provinces of China and Tibet, rhubarb has been culivated for over 5000 years for its medicinal purposes. It is first mentioned in the Chinese herbal Pen-King, which listed it as being used as a purgative and stomachic, but more 'modern' uses have it down as being used as an insecticide, a hair dye, and even to clean burnt pans.

It found its way to the West via Turkey and Russia, and was first planted in England by an apothecary named Hayward in 1777. It soon found its way into the kitchens, where its tart flavour of the became popular in desserts such as Rhubarb Crumble, as well as in jams, jellies and sauces.

Rhubarb stalk can be cooked, or eaten raw with some people dipping raw stalks in sugar to remove some of the tartness. It should be noted that generally only the stalk of the plant is eaten, as the leaves of this plant contain Potassium Oxalate. In large quantities this substance can sometimes cause poisoning, occasionally fatal in people with a suceptability to oxalic acids.

Sources include
http://www.botanical.com/botanical/mgmh/r/rhubar14.html http://www.rhubarbinfo.com/