Sweet fennel is a native Mediterranean plant and has widely naturalised and escaped from cultivation worldwide. We aimed to study the changes occurred in the physical, chemical and biochemical characteristics during development and under cold storage to determine the maturity stage and the most suitable age for harvesting. Two experiments were carried out on sweet fennel cultivar "Florence" in the winter seasons of 2016-2017 and 2017-2018 at a private farm located in Behiera Governorate. Bulbs of 70, 90, 110, 130, 150 and 170 days age from seed sowing were examined The obtained results showed that there were gradual increases in the bulb fresh weight, size and diameter till the age of 130 days after which a rapid increase took place up to the last examined age of170 days exhibiting statistically a curvilinear pattern. However, the bulb firmness increased gradually with the age proceeding till 170 days age. Moreover, an increase in the T.S.S, ascorbic acid and antioxidant activity was detected up to the age of 130 days then followed by a decline up to the age of 170 days showing statistically a curvilinear shape. Furthermore, storing the developmental stages at 15ºC and 95% RH showed that the bulbs of 130 days age reflected the minimum loss in weight and the lower unmarketable percentage during storage and the highest contents of T.S.S, ascorbic acid and antioxidant activity. From the obtained results, it was clear that the bulb maturity stage of the variety Florence of sweet fennel was reached after 130 days and this age was fortunately the most suitable age for harvesting.