Rhubarb, or Pieplant, a heavy-leafed perennial garden vegetable related to buckwheat. One species is grown for its thick, juicy, rose-colored leafstalks, which are stewed and made into a tart sauce or pie-filling. The leaves, which grow at the end of the tall, hollow stalks, must never be eaten, however. They contain enough oxalic acid to cause serious, sometimes fatal, poisoning. Small, greenish-white flowers blossom above the leaves at the top of each stalk.

Rhubarb, which may have originated in Asia Minor, is grown easily in cool, temperate climates. A winter crop of common garden rhubarb is grown by exposing the crowns (the bud-bearing parts, which lie between the stem and root) to freezing weather, and then allowing them to grow in enclosures kept at a temperature of about 60º F. (16°C). This process is called forcing.

Common garden rhubarb is Rheum rhaponticum. Another species, R. palmatum, is sometimes grown for its handsome leaves. Rhubarb belongs to the family Polygonaceae.