Operational nursery environments shape the morphological quality of container-grown forest seedlings beyond species and stocktype

Understanding container seedling quality is crucial for determining post-planting survival and early growth, yet the contribution of operational nursery environments to morphological variation in seedlings remains poorly quantified. This study examined shoot height (H), root collar diameter (RCD), and the height to diameter ratio (H/D ratio) of 4835 container-grown seedlings representing seven species across five nurseries affiliated with the Gyeonggi Province Nursery Association, South Korea. Nursery identity explained 46.8%, 32.8%, and 66.6% of total variation in H, RCD, H/D ratio, respectively, in Pinus strobus (stocktype 2 +2, P < 0.01), demonstrating substantial morphological variation among operational nurseries. At one nursery, production records documented the omission of a scheduled transplanting step from 6-cell to single-cell containers. In the older stocktype, both P. strobus and Chamaecyparis obtusa showed greater shoot height without a corresponding increase in RCD, together with high H/D ratios. In P. koraiensis (stocktype 3 +0), shoot height differed 2.72-fold between two nurseries with contrasting documented fertilization management, whereas RCD differed by only 1.18-fold. Across all species, median H/D ratios ranged from 32.5 in P. koraiensis to 154.8 in Betula pendula , confirming substantial species dependence. These findings indicate that operational production histories are associated with distinct morphological patterns and that H/D ratio should be interpreted together with its component traits and production context. Integrating routine morphological monitoring with production history records may improve the consistency of quality assessment and help identify unusual morphological patterns before seedlings leave the nursery.