Improvement of compactness and floral quality in azalea by means of application of plant growth regulators

The ornamental industry's difficulties in producing compact and well branched plants have been the subject of extensive evaluation, the problems being compounded by the fact that each species, and even each cultivar, requires a specific protocol. In this work, growth regulators (daminozide, paclobutrazol and chlormequat chloride) and chemical pinching agents (fatty acids) were applied to reduce shoot extension with a view to lowering production costs whilst optimizing plant quality in the production of azalea japonica. Assessment of the effectiveness of the different treatments was achieved using image analysis as a quantitative method which we consider to be a faster and more objective technique than classic biometry. The results indicate that daminozide and paclobutrazol treatment are the best options to control vegetative development and to promote the flowering of azalea japonica in a cold and humid zone such as Asturias. However, daminozide treatment induces floral deformation in one of the tested cultivars, Blaauw's Pink.