Rhubarb, like asparagus, is a perennial vegetable. It is harvested for the leaf stem, which is also called a petiole. Some years rhubarb will produce large, hollow-stemmed seedstalks that arise from the center of the plant. These should be broken or cut out as they appear so that energy will go into plant vigor rather than seed production. It will take several weeks for all the seedstalks to appear so be vigilant in removing them. Newer varieties of rhubarb are selected for vigor, bright red-colored stalks and less of a tendency to produce seedstalks than the older types. (Ward Upham)
