A Genma Tree is a large Genma that resembles a cherry blossom tree. Genma Trees are actually created from a mass of human corpses with the souls trapped in antagonizing pain. In time, the Genma Trees produce Genma Insects which are eaten by humans and cause them to either become Genma or turn into Genma Trees themselves.
During the events of Onimusha: Dawn of Dreams, Hideyoshi Toyotomi and the Genma under Claudius, Rosencrantz, and Ophelia act to gather the Genma Trees to Kyoto to use in conjunction with the Mother Genma Tree to bring about the resurrection of Fortinbras. However, the Mother Genma Tree reverts back to Lady Yodo while Soki sacrifices himself to wipe out the remaining Genma trees.