Citrus Flowering and Fruit Setting

In citrus, flowering is a regular process under tropical and subtropical climates, unless external conditions harmonized it into a precise period of intense bloom. During winter, air and soil temperature of subtropical areas drops below about 15°C for some months, causing the cessation of growth for 3–4 months. This phenomenon enables the plant to tolerate frost damage and brings about changes within the buds, encouraging flowering when exposed to a warmer temperature. In subtropical areas with cold winters, citrus blooms abundantly in the spring and has only one main crop which depending on the variety and seasonal temperature regime, matures in late fall or winter, or even the following spring. In citrus, flower development is encouraged by low temperatures or drought. A citrus fruit has a sigmoid growth habit, taking place in three phases cell division, enlargement, and maturation. Climatic variables (water and temperature) and some endogenous factors (hormones and carbohydrates) affect fruit growth.