Rationalization of Camellia japonica L. pot cultivation: a multidisciplinary approach

Camellia japonica L. is an evergreen flowering perennial with more than 3,000 named cultivars of great ornamental value. These are nowadays traded worldwide as containerized small sized plants. Cultivation of ornamental plants is strongly oriented to sustainable production on the one hand and on a consumer-oriented high quality product on the other hand. In this context, the present work concerned a series of critical points of the cultivation cycle of potted C. japonica: the reduction of fertilization; the choice of a peat alternative substrate; the regulation of plant growth for size and flowering control; the control of the dormancy release of flower buds. Experiment 1 concerned the application of commercial biofertilizer inocula which included a specific arbuscular mycorrhizal fungus (AMF) isolate or a consortium of microorganisms (AMF, saprophytic fungi and helper bacteria) as alternatives to inorganic fertilization of pot cultivated C. japonica. To deepen AMF role, Experiment 2 evaluated potential specific isolates associated with camellia roots (active population) or surrounding soil (potential and soil exploring population) of centennial specimens found in natural or semi-natural ecosystems. Experiment 3 assessed the efficacy of flurprimidol and three peat alternatives (nutshells, rice husk, coconut fiber) on camellia growth control. Finally, Experiment 4 used a multidisciplinary approach to describe and characterize the effects of cold treatments on the dormancy release of flower buds. Overall, the results highlighted that C. japonica is susceptible to AMF inoculation and that a series of benefits can be achieved by inoculating pots with specific symbiotic fungi. Moreover, two newly tested materials (nutshells and rice husk) were suitable as partial peat alternatives (30% v/v), and the efficacy of very low concentrations of flurprimidol to control growth and enhance flowering was underlined. Lastly, the use of cold treatment allowed the achievement of an earlier, uniform and enhanced flowering