Pseudobulb Yield and Chemical Quality of Field-Grown Bletilla formosana in Guangfu, Hualien, Across Cultivation Years and Harvest Seasons

Abstract

Bletilla formosana is an important medicinal orchid in Taiwan, but information on how cultivation year, harvest season, and pseudobulb size are associated with yield and chemical quality under field conditions remains limited. This study evaluated field-grown B. formosana in Guangfu, Hualien, Taiwan. Plants cultivated for 1, 2, or 3 years were sampled in winter and summer, and pseudobulbs were classified as large or small using a 3 cm threshold. Agronomic traits, photosynthetic pigments, pseudobulb yield, and chemical constituents were evaluated, followed by hierarchical clustering and correlation network analysis. Pseudobulb biomass was generally greater after 2–3 years of cultivation; for example, total pseudobulb dry weight in winter increased from 18.7 g m–2 after 1 year of cultivation to 178.1 g m–2 after 3 years. Photosynthetic pigment parameters did not differ among cultivation years. All winter treatments met the Taiwan Herbal Pharmacopeia requirement for militarine (19 mg g–1 DW). In Summer 1 Y, militarine content was 17.79 mg g–1 DW in large pseudobulbs, slightly below the requirement, compared with 56.31 mg g–1 DW in small pseudobulbs. Small pseudobulbs from the winter 1-year group showed relatively high total phenolics and several secondary metabolites, while carbohydrate-related constituents were more prominent in summer small pseudobulbs. Hierarchical clustering and correlation network analysis revealed distinct season- and size-dependent patterns of chemical composition and constituent associations. Overall, cultivation for 2–3 years followed by winter harvest provided the most favorable balance between pseudobulb yield and militarine compliance, while pseudobulb size grading may help distinguish materials with different chemical profiles.