Assessment of seasonal, substrate and hormonal factors influencing the propagation and rooting of <i>Camellia rubriflora</i> ’s cuttings

Camellia rubriflora (C. rubriflora), a member of the genus Camellia, is an endemic species in the northern mountainous region of Vietnam. However, overexploitation of this species has placed it at risk of extinction, and conservation strategies need to be implemented to ensure its continued survival. This study evaluated the ex-vitro propagation potential of C. rubriflora using cuttings obtained from a nursery. The effects of seasonality, rooting media, and NAA concentration on survival rate, bud break rate, rooting ability of cuttings were investigated. Spring propagation of cuttings performed significantly better than those in other seasons. Using a rooting medium composed of soil and carbonized rice husk, combined with 150 ppm NAA, significantly enhanced growth parameters, achieving a 77.8% survival rate, 94.4% bud break rate, and 72.2% rooting rate, significantly higher than the control using soil without NAA. Root number and root length were also significantly increased under optimal conditions, reaching 5.2±1.0 roots per cutting and 9.4±0.9 mm, respectively. The high correlation between survival rate, bud break rate, and rooting rate was observed, especially when using Soil+CRH, ranging from 0.709 to 0.843, showing the simultaneous impact of experimental factors on the evaluation criteria. Evaluating optimal conditions for the propagation of C. rubriflora played an important role in enhancing the conservation potential of this endemic species at risk of extinction.