An untrimmed olive tree slowly transforms into a rounded bush, with the furthest (distal) branches that vegetate and bear fruit, while inside the branches progressively lose their leaves: in fact the olive tree is a plant in which the growth of the branches it is greater in the part closest (proximal) to the central stem, and is surrounded, if not pruned, gradually, by branches that rise vertically, filling the central part of the tree, with the fruiting part relegated to the top; plants in which the central stem is greater than the distal ones are called basitone.
Man therefore tries to modify this bushy growth, making sure that the fruiting part is easily reachable for harvesting, and controlling the vegetative growth of the plant itself, eliminating the fruitless branches: in the olive tree, at the end of pruning, the light!
But how to deal with an olive tree ???? It is not easy!!!!!!! But some things are easy for everyone! Me too! First of all, via the suckers, those branches that rise straight up, both on the lateral branches and on the trunk, via the suckers, other straight branches that generally start from the stump of the plant … (attention that suckers can also become fruiting if they are generally sterile. I generally stop here … to let the expert’s hand, not to touch the extension branches (they are those branches that rise obliquely and tend to lower) and the fruiting branches, that is the branches that the following year they will bear fruit! In fact the fruits are born on the twigs that are born in that year, less on those two or more years ..
Why can an olive tree be filled with suckers and suckers? The suckers are born from latent buds, present both on the trunk and on the lateral branches, the excessive growth of these denotes an excessive vegetative activity of the olive tree, due either to large pruning, or to too much fertilization or too much spraying … …

here a small video of a pruner at work ..