Plants interact with fungi in their natural growing environments, and relationships between plants and diverse fungal species impact plants in complex symbiotic, parasitic, and pathogenic ways. Over the past 10 years, we have intensively investigated plant growth regulators produced by mushrooms, and we succeeded in finding various regulators from mushroom-forming fungi: (1) fairy chemicals as a candidate family of new plant hormones from Lepista sordida, (2) agrocybynes A to E from fungus Agrocybe praecox that stimulate strawberry growth, (3) armillariols A to C and sesquiterpene aryl esters from genus Armillaria that are allelopathic and cause Arimillaria root disease, and (4) other plant growth regulators from other mushrooms, such as Stropharia rugosoannulata, Tricholoma flavovirens, Hericium erinaceus, Leccinum extremiorientale, Russula vinosa, Pholiota lubrica and Cortinarius caperatus.