Trachystemon orientalis, commonly known as Abraham-Isaac-Jacob, is a perennial herb of the family Boraginaceae. This plant prefers the shadows of hygrophytes deciduous forests. Its large green leaves can be clearly outlined in the foliage. Despite the solid cloth on them, the forest dwellers prefer its taste, which the reason why the leaves are often ripped at the edges. Small blue-violet flowers with protruding stamens are located outside of high-branched stems. This perennial herb usually reaches a height of 20 cm to 60 cm. Trachystemon orientalis is a species recorded in Bulgaria's Red Book as rare.
Trachystemon orientalis is native to most of Strandzha Mountain, but can be found only in one other location in Bulgaria – the Eastern Rhodopes. The species is representative of the South Black Sea (Euksin) floral elements, preserved as relicts in Strandzha. This is an example of the close connection between Strandzha Mountain’s flora and the Pont-Euksin flora of the Caucasus and Asia Minor. In the past, 7500 years ago, between Strandzha and Asia Minor there was a broad land connection, ensuring the free circulation of South Black Sea vegetation. During the Quaternary glaciers covered most of Europe, but in Bulgaria solid glaciers are formed only in the high parts of Rila and Pirin Mountains. The warm and humid climate in the valleys of Strandzha during this critical period helped the preservation of ancient plants called relics in the area. They define the specific habitat of Strandzha Mountain, as well as attract tourists from all over Bulgaria and worldwide.