Top-geoherbs of traditional Chinese medicine: common traits, quality characteristics and formation.

Top-geoherbs used in China are always featured with high qualities, and they grow in specified areas with specific environment. Recently, researches on top-geoherbs have attracted increasing attention in China and other countries. In order to have a thorough knowledge of top-geoherbs, this article reviews the concept, historical evolution, common trait and quality characteristics of top-geoherbs, and explains the forming mechanism including genetic mechanism and environmental mechanism. In addition, it introduces the influence of human factors on the quality of top-geoherbs. Finally, it proposes some problems that should be paid attention to in the researches on top-geoherbs.