The olive is an evergreen plant that can grow as a shrub, hedge, or tree. Olive trees can grow as tall as 30 feet. Olives bear small pitted fruits that can be cured for table consumption or pressed for oil. Some olives are grown for ornamental use, often as shrubs or hedges–the olive’s narrow gray-green leaves offset the dark green of most gardens and the olive’s branching is noted for its billowing form.
Olive trees grown for their fruit are best trained and pruned to a manageable height–from 12 to 15 feet tall–the shorter stature will allow for an easier harvest.
Pruning olive trees. Olive trees fruit along one-year-old wood usually at the periphery of the tree canopy. Prune each year to encourage wood that will fruit. Thin out broken, diseased, and unproductive wood. Head back drooping wood and prune out water sprouts. Olives are best trained on trunks 3 to 4 feet tall with 3 to 4 scaffold or main lateral branches trained or pruned to different direction beginning at about 4 feet from the ground. (Multi-trunked olives are often used ornamentally, but can be kept to a manageable height for harvesting. Don’t allow multi-trunked trees to grow too dense in the center.)
Train and prune olives to an open center allowing sunlight to reach deep into the crown of the tree. Remove basal sprouts; pull them away don’t cut them to make sure they do not regrow. Rub off buds near the ground level that may become suckers. Olives that go unpruned will become densely twigged and crowded.
When to prune. Prune olive trees in early spring before buds and flowers set. Olive trees can be thinned any time of the year without damaging the tree. However, if you prune in late spring or summer after flowering, the harvest is likely to be decreased. You can prune in winter if the weather is frost-free and dry. Prune in dry weather to allow cuts to heal before frost or rain. Regularly pruned olives will require less pruning and thinning than trees that have been neglected. In regions with severe droughts, pruning in summer will reduce the number of leaves competing for water and may enhance the harvest.
Thinning the fruit for harvest. Olives fruit from the leaf axial along one-year-old wood or stems, not at the end of stems. Three to four fruits per foot are sufficient for a good crop. Thin away extra fruit to increase the size and oil content of the fruit on the tree. Thinning will also hasten the harvest and allow for a good harvest the next year. Olives are best thinned in late spring or early summer several weeks after the initial fruit set. Hand thinning is the most effective way to thin.
Training new trees. Train new trees to have a clear trunk 3 to 4 feet tall. Prune away side branches below where you want the main scaffold to branch; the main scaffold should begin at 4 to 5 feet from the ground. Select 3 or 4 well-spaced laterals or branches to form the main scaffold. Train these young branches in the desired direction away from each other.
When to begin training a new tree. There are two schools of thought on this. Some begin training new trees immediately, selecting a leader to become a trunk and then encouraging select laterals to form a scaffold. Others allow olive trees to grow for 3 or 4 years almost as a shrub before beginning to prune and train. This strategy allows the tree to gain strength and even begin to bear fruit before the main trunk and scaffold branches are selected.
Renovating a mature tree. An overgrown and unattended olive should be pruned to regain the tree’s form and open its crown to sunlight. Prune to establish a clear trunk 3 to 4 feet tall. Prune out broken, dead, diseased, and unproductive wood first. Prune to establish a crown with 3 to 5 main branches. Once the main scaffold is established, thin out new shoots to open the tree to sunlight and continue to prune away suckers and water sprouts on a yearly schedule. An olive tree will recover from a heavy pruning. Pruning will stimulate and encourage the growth of new fruiting wood.