Description B Magic Mushroom Grow Kit B Magic Mushroom Grow Kit. B is a strain of Psilocybe cubensis, a well-known hallucinogenic mushroom species. The B strain is popular with growers because it is easy to work with, accepting a very wide range of growing conditions and substrates and producing large, thick caps. Though not the fastest-grower among P. cubensis strains, B is not the slowest, either.
