B+ Europe mushrooms. B+ is a variety of the well-known hallucinogenic fungus Psilocybe cubensis. The B+ strain is popular among growers because it is easy to deal with, accepts a variety of growing environments and substrates, and yields huge, thick heads. The Psilocy cubensis strain B+ does not grow the fastest or the slowest. Depending on the growing environment, color varies significantly; enthusiasts describe the enormous golden to caramel-colored crowns as “beautiful.”