Pruning Query - Pittosporum Tenuifolium Silver Queen - Privacy Screen In Planters

Hello.

On my roof terrace I have 8 Pittosporum Tenuifolium Silver Queen plants in 4 large wooden planters situated along the perimeter wall (2 plants in each planter). The reason is for both privacy and to allow a decent amount of sunlight through, as opposed to a dense hedge.

As can be seen on the first photo the bottom two thirds of the plants are void of leaves... apart from the odd ones at the end of leggy stems the leaves are situated at the top third.

I would like to know if it's possible to hard prune them into their thick trunks quite low down in the hope that new branches grow with leaves covering the bottom area as well as the rest?

The plants are about to begin this year's new growth.

Interestingly I have two different types of Pittosporum Tenuifolium Silver Queen's and the problem is only with this variety, which has small leaves and dark wood. Photo 2 shows the other variety which has never been a problem, having larger leaves and lighter wood - it has enough branches hanging downward and the larger leaves to create perfect privacy without being too dense therefore allowing light through. Maybe it has something to do with the position, as the variety that is fine is along a different aspect.

Photo 1 (problem plants):



Photo 2: