The Effects of Different Container Types and Substrate Ratios on the Growth Characteristics of Zelkova schneideriana Hand.-Mazz. Seedlings

To optimize container seedling cultivation of Chinese zelkova (Zelkova schneideriana Hand.-Mazz.), a three-factor completely randomized design was used to systematically evaluate the effects of container material, container size, and substrate composition on seedling growth, physiological traits, and root morphology. Different container materials, three container sizes, and multiple composite substrates were tested. Seedling height, biomass accumulation, photosynthetic characteristics, and root morphological indices were measured, and principal component analysis combined with comprehensive evaluation was applied to identify optimal treatments. The results showed that container size was one of the major factors affecting overall seedling quality, with large containers generally enhancing seedling height, biomass accumulation, photosynthetic capacity, and root development. Among container materials, B-type containers generally exhibited better overall performance under medium- and large-size conditions. Substrate composition showed a significant regulatory effect under appropriate container conditions, and the T3 composite substrate, composed of yellow soil (40%), peat (10%), sphagnum peat (15%), vermiculite (10%), rice husk (15%), and corn cob (10%), achieved the highest comprehensive score. According to the PCA-based comprehensive evaluation, the T3/A3 treatment ranked first, followed by T3/B2. Overall, the combination of B-type containers, appropriate medium-to-large container size, and the T3 substrate showed superior nursery performance. In particular, T3/A3 ranked first in the comprehensive evaluation, followed by T3/B2, indicating that both large black plastic containers and medium-sized B-type containers performed well under the T3 substrate.