The olive tree, Olea europaea, is a long-lived evergreen crop native to the Mediterranean. Although these trees do not shed all their leaves seasonally, they constantly replace their foliage. New leaf production is a necessity for maintaining photosynthetic capacity. The rhythm of this renewal is closely tied to the seasons, resulting in distinct periods of rapid growth and times of near-dormancy.
The Annual Cycle of Vegetative Growth
The most substantial flush of new leaf growth begins in early spring, following the period of winter rest. As temperatures climb, the tree directs stored energy toward shoot and leaf production. This primary growth phase typically starts in March and continues vigorously through June, depending on the local climate.
During this time, buds open, developing into either vegetative shoots, which produce new stems and leaves, or floral shoots. The new leaves emerge in a predictable pattern, with two leaves growing in opposite directions at each node. A secondary, less intense period of vegetative growth often occurs in the autumn, provided conditions are mild and moisture is available.
Growth slows down significantly, or halts entirely, during two other times of the year. In the winter, cold temperatures induce dormancy. In the heat of summer, high temperatures and water stress cause the tree to enter summer dormancy. This shutdown protects the plant from excessive water loss, limiting new leaf production until conditions improve.
Environmental Factors Driving Leaf Production
The initiation and speed of new leaf production are governed by specific environmental triggers, primarily temperature and water availability. Vegetative growth, including new leaf development, generally requires a lower threshold temperature (LTT) for the shoots and crown between 13°C and 14°C.
The optimal temperature range for this growth is between 20°C and 25°C; temperatures above 25°C begin to slow down new growth. Roots must also be active to supply the necessary water and nutrients, a process that relies on warm soil temperatures.
Adequate water availability, often following winter and spring rains, is also a necessity because rapid growth cannot be sustained under dry conditions. Conversely, when air temperatures exceed approximately 30°C, the tree minimizes water loss by closing its stomata. This dramatically reduces photosynthetic activity and stops new leaf growth.
Leaf Longevity and Natural Shedding
The appearance of new leaves is part of the continuous foliage renewal characteristic of the olive tree’s evergreen nature. Individual olive leaves have a defined lifespan, typically remaining on the tree for an average of two to three years. This longevity allows the tree to maintain a canopy year-round, an adaptation to its native Mediterranean climate.
As an individual leaf nears the end of its lifespan, it undergoes senescence, often turning yellow before detaching from the branch. This natural shedding is a gradual process that happens throughout the year, meaning the tree never appears bare.
The greatest amount of leaf drop is often observed in late winter and early spring, just before the main flush of new growth begins. This timing allows the tree to shed older, less efficient foliage while simultaneously producing fresh, highly productive leaves.