California poppy (Eschscholzia californica), a member of the Papaveraceae, is native in west coast of North America, and globally used as ornamental plant with its beautiful flower. This plant is also used as herbal medicine, because it produces various types of benzylisoquinoline alkaloids (BIAs), i.e., aporphine-, pavine-, protoberberine-, protopine-, and benzophenanthridine-type alkaloids. So far, the major alkaloid biosynthesis pathways and biosynthetic enzymes of these BIAs in this plant species have been characterized at the molecular level. Because of its relatively small genome size (502 Mb), the genome sequence of this plant species has been determined to study genome structure of BIA biosynthetic enzyme-encoding genes and the evolution of BIA biosynthesis in land plants.