Karl Foerster was one of the most significant perennial gardeners and breeders of the early 20th century, as well as a successful writer. "The Blue Treasure of Gardens" is one of his masterpieces. This book contains nearly all of Karl Foerster's historical texts and continues to provide a unique poetic reading pleasure even today. The historical texts are complemented by current contributions on new developments in the field of blue plants and their use throughout the gardening year, written by selected experts.