Boron deficiency in olives
Native to the Mediterranean region, tropical and central Asia, and various parts of Africa, olives require a long, hot growing season to properly ripen the fruit, no late spring frosts to kill the blossoms, and sufficient winter chill to insure fruit set. Olives are also grown commercially in California, Australia, and South Africa.
Olives will grow and produce fruit even on extraordinarily poor, stony soils, yet they respond to fertilizers.
Boron is a crucial trace element for olive trees. Fertilizing olive trees with adequate boron is necessary for:
- Flower formation
- Fruit set
- Quality olive oil
- Stable olive oil
Boron deficiency makes leaves fall and branches die in the upper parts of the tree. Secondary shoots develop at the base of the dieback, and the number of suckers in the lower part of the trunk increases.
The leaves show a distinct apical browning which can extend up to two-thirds of the leaf while the rest of the leaf remains a normal green color. Subsequently, the leaves may become completely yellow and later turn a leathery brown from the apex. In cases of mild boron deficiency, some fruit may ripen normally but most will drop prematurely or become deformed and corky. As the boron deficiency becomes more severe, the olive tree will become increasingly less productive and may ultimately die.