Hildegard von Bingen (1098-1179), abbess at the head of three monasteries in twelfthcentury Germany, experimented many medicinal plants on the sick people. From these experiences, she wrote a unique medical treatise entitled Physica whose book I is mainly devoted to medicinal plants, some of which remain unknown today. The purpose of this work was then to try to identify these plants and compare their medicinal uses between the Hildegard era and the 21st century. After a first part that puts Hildegard in the historical context of the time, then come the medical sources on which Hildegard was able to rely on for the writing of his work of medecine. A biography of this visionary follows. Elements for the identification of plants are included ...