Phenological growth stages of Dendrobium moniliforme (L.) Sw. according to the extended BBCH scale

Dendrobium moniliforme (L.) Sw. is a rare and endangered epiphyte plant of Orchidaceae with significant medicinal and ornamental value in China. It is necessary to use artificial cultivation to protect the wild resources because of its difficulty to survive in the wild. To date, more and more researchers have paid attention to the importance of phenology in stem development, flowering, pollination and fruiting of Dendrobium, but no specific and detailed phenological scale was set. Based on the extended BBCH scale, we used morphological and anatomical techniques to observe and record the growth and development characteristics of D. moniliforme. As a perennial herb, the growth process was divided into juvenile period and adult period. The juvenile period can be divided into two phases: seed germination (0) and seedling morphogenesis. Four stages are composed of the seedling morphogenesis, i.e. leaf development (1), formation of side shoots (2), stem (protocorm) elongation (3) and adventitious root formation (4). The adult period can be divided into vegetative growth and reproductive growth phases. Vegetative growth phases include bud development (0), leaf development (1), shoot development (3), root development (4) and dormancy (9). The reproductive growth phases include inflorescence emergence (5), flowering (6), development of fruit (7) and ripening of fruit and seed (8). For the entire growth and development process of D. moniliforme, 74 secondary growth stages were further coded and described. Additionally, the time series of different development stages in the annual growth cycle were discussed. This extended BBCH scale may provide guidance for the production and management practices of D. moniliforme.