Influence of greenhouse climate and plant density on external quality of chrysanthemum (Dendranthema grandiflorum (Ramat.) Kitamura):: First steps towards a quality model

The effects of greenhouse climate and plant density on external quality of chrysanthemum (Dendranthema grandiflorum syn. Chrysanthemum morifolium) are reviewed. The external quality aspects analysed in this paper are stem morphology (length, diameter and "strength") leaf morphology (number and size) and flowering aspects (number, size and position). Increasing assimilate availability level (e.g. higher light intensity, higher CO2 concentration and/or lower plant density) has a positive effect on several external quality aspects of chrysanthemum. It results in longer stems, more lateral branches, a higher number of flowers and increased flower size per plant. Furthermore, both temperature and daily light integral are the main factors that determine stem elongation and time to flowering. Time to flowering is not affected by the CO2 level. In general it can be concluded that each external quality character is influenced by several growing conditions interacting with each other. Therefore, the development of an explanatory model, as a climate control tool to predict and optimize external quality in year-round chrysanthemum production, would be of utmost importance. To build such a model detailed and integrated information about chrysanthemum growth and development is needed. This review intends to serve as a starting point for modelling external quality of cut chrysanthemum.