The Tibouchina is a fabulous plant. Some to look out for include Tibouchina 'Kathleen', with its beautiful, mauve-pink flowers. Another that's popular is Tibouchina mutabilis 'Noelene' - the flower starts white and turns to a mauve-pink. It mutates hence the name - mutabilis. And Tibouchina lepidota 'Alstonville' is covered in masses of purple flowers from autumn right through to winter. It's called Alstonville because it was developed in Alstonville in northern New South Wales.

The plants filmed by Gardening Australia are in a garden in the hinterland of the Sunshine Coast where the soil is acidic - absolutely ideal for Tibouchinas. If the soil is not acidic enough the leaf burns at the edges, turns brown and eventually the leaf dies. If that happens correct the soil acidity by adding sulphur on the ground, around the roots, or use an acidifying fertiliser.

They do need pruning, otherwise they will grow into a fairly large tree. Afer they finish flowering, prune the plant back. Delaying the pruning means you throw the whole flowering season out of kilter and this will result in spasmodic flowering.

Link- http://www.abc.net.au/gardening/factsheets/tibouchina/9428216