Height control in ornamental plants: sustainable alternatives to growth regulators. The need to find sustainable and efficient strategies to control plant height is currently a great challenge in the protected cultivation of ornamental plants. The aim of this study was to: (1) analyse the available information on the factors involved in plant height; (2) understand the underlying physiological mechanisms behind stem elongation; (3) define sustainable alternatives for producing compact floricultural crops, reducing the application of chemical growth retardants to a minimum level. It was concluded that keeping a night temperature higher than the day temperature (negative DIF or DROP treatment) or changing the light quality (high red/ far-red ratio) have a high potential as non-chemical methods for controlling plant height in several species of ornamental plants. Increasing the red/ far-red ratio can be done in different ways including the use of photoselective films and/or using several easy to apply measures, including: (i) avoiding very high plant densities; (ii) using supplementary light with a high red/far-red ratio (e.g. assimilation lamps instead of incandescent lamps); (iii) avoiding plant exposure to the twilight period (due to the natural reduction of the red/far-red ratio). Mechanical stress is also an effective strategy for producing compact plants in some species. Furthermore, plant breeding might offer good possibilities for developing dwarf cultivars. Nevertheless, in most cases, it will not be one single measure that will result in compact plants, but it is rather the combination of several strategies.