Olive trees (Olea) are native to areas of the Mediterranean, Africa and Asia. Although their need for warm temperatures makes them difficult to grow outdoors in most areas of the UK, olive trees make attractive houseplants. Unfortunately, certain adverse conditions can cause the leaves to wilt and fall from the tree.
Dropping leaves are often a sign of poor health due to improper care. Olive trees require plenty of bright light. Keeping your potted olive tree in a sunny window will help provide adequate light. Transferring it to a sunny porch or patio during the summer may help enhance its growth and appearance. This type of tree prefers slightly moist soil near the roots. Lack of water can cause the leaves to dry out and wilt.
Olive trees are prone to certain illnesses. The most common type of fungal disease is verticillium wilt, a disorder that attacks the roots of the tree and often results in the loss of the entire plant. The first symptom is sudden wilting of the leaves early in the growing season. While some of the wilted leaves may fall from the tree, many remain on the branches. Although fungicides may help, there is no proven remedy for this fungal disease. Olive knot is a bacterial disease that can affect olive trees. In addition to stressing the tree to the point of leaf loss, olive knot disease causes gall formation over wounded areas of the tree. Pruning off the affected growth will help eliminate the spread of this illness.
In outdoor settings, the major pests that damage olive trees include the olive moth, olive-kernel borer, olive fruit fly and black scale. However, olive trees grown as houseplants can experience the same pests as other plants in the vicinity, such as spider mites. Removing the damaged areas and quickly treating a pest infestation with an appropriate pesticide can help limit the damage. Treating other houseplants at the same time will decrease the risk of new infestations.
The best way to determine whether leaf loss is due to a nutritional deficiency is to test the soil in the pot surrounding the olive tree's roots. While calcium, phosphorus, potassium and boron are all important to healthy growth, a lack of nitrogen is the most likely cause of a nutritional deficiency that causes the leaves to wither and fall. Applying a nitrogen fertiliser formulated for fruit-bearing trees can help improve the health and appearance of the tree.