Harvest season outweighs provenance in determining the phytochemical and mineral quality of Cyclocarya paliurus leaves: A common-garden basis for multi-objective harvest timing

Cyclocarya paliurus is cultivated as a medicinal sweet-tea crop whose raw-material quality depends on leaf chemistry. This study quantified the relative contributions of harvest month and provenance to leaf composition and identified candidate harvest windows for different end-uses. A common garden comprising 11 provenances and 32 open-pollinated families was sampled from June to October 2020 for eleven constituents: three flavonoids, total triterpenes, polysaccharides, β-sitosterol and five mineral elements. In the complete eleven-trait profile (38 provenance-by-month means), harvest month explained 57.1% of multivariate variation and provenance 19.4%. Across sequential and marginal partitions with and without selenium, the corresponding shares were 50.4–57.1% and 19.4–20.9%. Constituents peaked asynchronously: kaempferol and isoquercitrin peaked in July, total triterpenes in September, and quercetin and polysaccharides in October. The composite flavonoid desirability was highest in October (1.00), followed by July (0.93). The mineral objective peaked in July, whereas the triterpene objective peaked in September. Combining four objectives identified October as the highest-scoring balanced window (0.85), with selenium excluded because of frequent non-detects and incomplete detection-limit documentation. These concentration-based results support end-use-specific harvest scheduling, subject to validation across sites and years and clarification of analytical and sampling limitations.