Quantitative morphometric analysis reveals morphological overlap among traditional sepal types in Cymbidium goeringii

Introduction Traditional sepal classification in Cymbidium goeringii relies on expert-based descriptions, but the quantitative basis and extent of morphological overlap among categories remain poorly understood. This study investigated the planar morphometric differentiation of traditional sepal categories. Methods A total of 1,380 floral-organ observations from 46 traditional cultivars were collected using a standardized scanning protocol. Morphometric descriptors were analyzed using linear discriminant analysis (LDA), with SMOTE balancing and stratified cross-validation to explore morphological separation among categories. Results Shui-xian-ban showed substantial morphological overlap with mei-ban, whereas zhu-ye-ban and he-ban exhibited relatively greater morphological separation. Sepal tip angle and sepal length contributed most strongly to the observed separation. Organ-specific misclassification patterns also highlighted the limitations of two-dimensional representation for capturing three-dimensional floral features such as qi-dou. Discussion The findings indicate that traditional sepal categories do not consistently correspond to distinct planar morphometric boundaries. Quantitative morphometrics provides an exploratory approach to characterizing morphological variation associated with traditional floral classifications, but the results do not establish a validated cultivar-authentication method. Independent cultivar-level and external validation across additional germplasm collections are needed to assess generalizability and practical applicability.