This work was carried out in the orchard of Toshka Horticultural Research Station, Aswan Governorate. It went on for two successive seasons (2018 and 2019). The work involved six mature Valencia orange trees. The trees were about 15 years old. All the investigated trees were on sour orange rootstocks. The objective of this experiment was studying the behavior of growth of Valencia orange trees grown under Toshka conditions. It was also decided to study the distribution of the newly developing shoots throughout the growth seasons. Results showed that all investigated trees trended to have two growth cycles (spring and summer cycles):
• The spring growth flush (main cycle) took place by the beginning of April till the end of May.
• The summer growth flush took place by the beginning of July till the end of October.
• All the new shoots started to grown slowly, then rapidly and gradually slowed down by the end of the period.
• The Valencia trees tended to bear the flowers on two types of growth. The first type was the new shoots (leafy inflorescences) that developed during April and May.
• The second type was the woody inflorescences that was borne on the old wood developed in the previous years.
• Fruit set was much higher in the leafy inflorescences than that on the woody type.
Results showed that all the investigated trees trended to have two growth cycles (spring and summer cycles) .The spring flush (main cycle ) took place.