Abstract: As a genuine medicinal material in North China, the ecological cultivation of Forsythia suspensa is a critical concern in the current production of medicinal materials. We investigated the morphological phenotypes, module quantities, and the module distribution pattern of F. suspensa with different numbers of main branch formed under ecological cultivation using hierarchical survey, as well as their impacts on the yield and quality. We found a substantial morphological plasticity in the crown width of F. suspensa, of which those with three to five main branches had a 1.64-fold difference compared to that with one branch (P<0.01). The plasticity of plant height and ground diameter was relatively small (P>0.05). The module numbers of branches, leaves, flowers, and fruits of F. suspensa exhibited high plasticity. According to the distribution pattern of F. suspensa modules, the branches of F. suspensa were distributed within 60-160 cm in the vertical direction and within the middle layer of the canopy in the horizontal direction. In terms of reproductive modules, the distribution patterns of flowers and fruits were basically the same as those of its branches. However, there were significant differences in fruit-setting rates at different locations. Vertically, the fruit-setting rate in the middle (60-140 cm) of the crown was higher than that in the upper and lower layers, with the highest rate at 80-100 cm (55.2%). Horizontally, the fruit-setting rate in the middle and outer (80-140 cm) of the crown was significantly greater than that in the inner layer, with the highest rate at 80-100 cm (69.4%). F. suspensa with one main branch and that with five main branches had distinct advantages in fruit yield, which are suitable for intensive and extensive management, respectively. In addition, F. suspensa with one main branch had the highest contents of volatile oil and forsythin, and the content of forsythoside A did not show significant difference from the highest value found in other types with different main branch numbers. Taken together, F. suspensa with one main branch is an excellent type among the five types with different main branch numbers, embracing higher economic benefits and medicinal value.

Key words: population module, Forsythia suspensa, phenotypic plasticity, quantitative characteristics, distribution pattern