ABSTRACT
The modern roses and most species of the genus Rosa form the subgenus Eurosa and are part of the family Rosaceae. In most species, the floral structure is based on 5 sepals and 5 petals. A full list of all the existing species and interspecies hybrids of roses is given in Modern Roses. Most species flower during the spring and summer seasons. The length of the period required for transition from the vegetative state to the first visible symptom of floral differentiation varies from 4 to 21 days, when the lateral shoots are 3 to 4 cm long, according to the cv or species and the temperature. A similar period of vegetative growth prior to flower differentiation has also been observed in rose seedlings and was defined as the juvenile period.
