Phenological growth stages of Magnolia ×soulangeana according to the extended BBCH scale

Magnolia × soulangeana, one of the most famous ornamental trees of Magnoliaceae, is widely cultivated around the world. However, its phenological characteristics at life-cycle scale have never been detailedly reported so far. In this article, the extended BBCH (Biologische Bundesanstalt, Bundessortenamt, und Chemische Industrie) scale was applied to divide the growth and development cycle of M. × soulangeana in both juvenile phase and adult phase, and describe the characteristics of phenological development stage, so as to provide theoretical guidance for its cultivation measures implementation. Based on the BBCH phenological scale, the processes of germination (0), leaf development (1), main stem elongation (3) and dormancy (9) were observed in the juvenile phase. Likewise, the morphological changes of organs in adult phase were abundant, and eight principal growth stages were described: vegetative bud development (0), leaf development (1), shoot development (3), reproductive development (5), flowering (6), fruit development (7), maturity of fruit (8) and dormancy (9). Our newly developed scale provides a unified standard for describing and identifying the phenological period of M. × soulangeana. In addition, it is of great significance to understand the phenological characteristics of M. × soulangeana for its breeding and cultivation management.