With the aim of shifting from vegetative propagation to seed planting and developing F1 globe artichoke hybrids, knowledge of the floral biology of the species is crucial, especially if extended to both male fertile and male sterile genotypes. Moreover, it is important to understand the causes and the expressivity of male sterility trait. The size of floral organs and the developmental stage have been analysed from the pre-meiosis to the anthesis phases. The developmental stage in ovules and anthers, relative to the progression of sporogenesis and gametogenesis, has been investigated by aniline blue, acetocarmine, and DAPI stainings. Male sterility did not produce any effect on the extent of both anther and time of the development. Male sterility is of pollinic type and the causing defect is represented by a postmeiotic block, probably due to a low nutritional activity of the anther tapetal cells and associated to a direct or indirect exine deposition. Differences in the female reproductive organs have been found, with ovaries and ovules more elongated in the male sterile clones respect to the male fertile ones and a hypothetical tendency to parthenocarpy. © ISHS.