Impact of mechanical stimulation on Hydrangea macrophylla

Plant compactness is a key feature of ornamentals plants grown in containers. It contributes to plant esthetical value, increases plant robustness, reduces culture and storage surfaces as well as transportation costs for trading. For a long time, chemical growth retardants have been commonly used by growers to control plant growth. However, current concerns about the preservation of the environment have led to the banning of several of these products. Alternative methods to chemical control of plant growth are thus urgently needed by producers. Mechanical stimulation mimicking wind impact on wild plants has proven efficient in reducing growth in several species, including ornamentals. However, not all plant species respond similarly to a given mechanical treatment. Therefore, research need to be carried out to find the efficient protocol that meet growers’ objectives for each species. Using an experimental set-up, different mechanical treatment has been used to investigate the phenotypical responses in three cultivars of H. macrophylla. It was concluded that mechanical treatment induced a significant reduction of stem elongation and an increase of stem diameter depending on stimulation material and cultivars.