Gardening - Vegetables: Selecting & Planting
The rhubarb or pie plant (Rheum rhaponticum) belongs to the Polygonaceae or buckwheat family. The plant is a herbaceous perennial with leaves growing directly from the crown. The leaf petioles or stalks are used in making pies, sauces and various tart food items. The leaf blades contain considerable soluble oxalic acid and are poisonous to humans. Less oxalic acid is present in the petioles. The lower concentration and the decreased solubility of the oxalic acid in the petioles make them edible for human beings.
Nutritionally, rhubarb provides appreciable amounts of Vitamins A and C. It also contains moderate levels of calcium and potassium. It is low in fats and carbohydrates but very acid. Its acidity requires the addition of considerable sugar, which greatly adds to the caloric content of ready-to-eat products made from rhubarb.
"SP291-Q-Rhubarb in Home Gardens," The University of Tennessee Agricultural Extension Service, SP291Q-2M-6/03(Rev) E12-5115-00-022-03, https://trace.tennessee.edu/utk_agexgard/45