Juglone is an aromatic organic compound with the molecular formula C10H6O3. It occurs naturally in the leaves, roots, husks, and bark of plants in the Juglandaceae family, particularly the black walnut. Juglone is an allelopathic compound, meaning it's synthesized by one type of plant and affects the growth of another. In the case of juglone, it's toxic or growth-stunting to many types of plants. Landscapers have long known that gardening underneath or near black walnut trees can be difficult.… (More on Juglone)