Plants are grown in a greenhouse in plant rows (1), between which plant row gaps (2) are provided. The greenhouse plants are illuminated in such a manner that they receive the light required for photosynthesis at least partly in a lateral direction from illuminators (10) moved along the greenhouse plant row gap (2) alongside the plants by directing light to each plant for part of the time. The illuminators may be arranged in arrays and fastened to carriages, for example.
