The term "jusei" means the growth or vigor of a tree, indicating its state of development. It is also called "momentum of the tree's spirit". Jusei applies to bonsai as a way of evaluating the quality and health of a tree, based on its branches, leaves, trunks and roots. Different tree species have different requirements for their cultivation, training and care, so bonsai tree identification is crucial to maintain good jusei. Jusei also refers to the properties of trees concerning their growth speed, shape, resistance to pollution and suitability for bonsai.