Effects of Planting Season, Planting Method, and Fertilization Regime on Survival and Early Growth of Camellia rubriflora

Single petal red camellia ( Camellia rubriflora ) is a rare endemic species with high ornamental, medicinal, and conservation value in northern Vietnam. However, its large-scale cultivation remains constrained by high mortality and inconsistent early growth due to the lack of standardized agronomic practices. This study provides a systematic evaluation of key cultivation factors affecting the establishment phase of C. rubriflora , aiming to develop an optimized technical framework for its sustainable production. Three independent experiments were conducted using a randomized complete block design (RCBD) with three replications at Thai Nguyen University of Agriculture and Forestry from 2023 to 2024. The study investigated the effects of planting season (spring, autumn, winter), planting method (open-field monoculture vs. intercropping), and fertilization regime (varying levels of organic manure combined with NPK 16: 16: 8) on survival rate and growth performance. Plant height, basal diameter, and survival rate were monitored over 12 months and analyzed using ANOVA and LSD tests (p < 0.05). The results revealed that planting season significantly influenced long-term plant performance, with spring planting achieving the highest survival rate (85.55%) and superior growth. Intercropping systems markedly improved microclimatic and soil conditions, resulting in significantly higher survival (88.89%) and enhanced vegetative growth compared with monoculture systems. The optimal fertilization regime was identified as 5 kg of well-decomposed manure combined with 0.3 kg NPK per planting hole, ensuring balanced growth and maximum survival (90.89%). These findings provide novel insights into the integrated effects of ecological and nutritional factors on C. rubriflora , offering a robust scientific basis for developing standardized cultivation protocols and supporting sustainable expansion of this valuable species.