Rhubarb, also called sweet round-leaved dock or pieplant, is usually thought of as a fruit, but it is actually one of the few perennial vegetables in existence. And the root can be used as medicine. Chinese rhubarb has a much stronger taste and properties than the common American variety. We generally use rhubarb root as a laxative and purgative for the treatment of both constipation and diarrhea, depending upon the dosage used.