The purpose of trimming olive trees is to open more of the tree up to sunshine. The parts of a tree that are in shade will not produce fruit. When you trim olive trees to allow sun to enter into the center, it improves the fruiting.  Don’t start trimming olive trees during their first year or its second year. You shouldn’t touch that pruner to your tree branches until the olive tree is at least four years old. During these early years, you should encourage foliage to form and leave it alone. A tree’s leaves produce its food, so having many leaves when the tree is young provides good energy for growth.

When it is time to shape the tree, remember that it is better to make a few, well-placed cuts than to make many small ones. You should use a lopper and a pruning saw to make these cuts.

Open-center or vase pruning is very common with olive trees. For this type of pruning, you remove the tree’s central branches to allow sunlight to penetrate the tree. Open pruning also increases the surface fruiting area of the tree.

After you have removed central branches and established a sound structure for the tree, all subsequent pruning is for maintenance. At that point, trimming olive trees involves only removing any growth that starts to fill in the center of the tree.

You can also keep down the height of the tree by pruning out the tallest branches. This is often important when you are pruning olive trees in containers. Use thinning cuts, not heading cuts, since the latter will stimulate new tall growth. Thinning cuts involve cutting something out, while heading cuts– also called topping cuts – involve cutting something off. Generally, you’ll want to use thinning cuts in olive tree trimming.

If you are wondering when to prune olive trees, it is between winter’s end and flowering. You can prune olive trees in spring or in early summer once the tree begins to open its flower buds. Pruning an olive tree while it is in bloom allows you to assess the probable crop before you trim.

Always wait to trim until the rains of winter are done, since pruning opens entry points for water-borne disease to enter the tree. An olive tree is more vulnerable to frost damage once it is trimmed, which is another argument for waiting until spring.

Hope this helps!