Sacha wrote:

Thinking of purple flowers, I heard from David P the other day that his
Hardenbergia violacea is going great guns and threatening to take over half
his neighbourhood.

It seems there are quite a few variants of H. violacea, although I
doubt that there are more than a few grown in the UK. I'm happy enough
with the vigorous purple form. I had a plant from Ray & Sacha last
year and decided to test its hardiness before giving it pride of place.
Last winter here was colder than any in the past 20 or so and it came
through unscathed, even managing to produce a few flower spikes. This
year it was planted against the wall next to the back door and has
raced up producing a mass of pleasing, deep sage green 'tongues'.
Already I can make out flower buds forming in almost every leaf axil so
I'm anticipating a good show of colour in late winter.

Moving on to Tibouchina, I've only tried T. urvilleana outside in
Torquay (in my previous garden) and it proved to be an excellent late
summer flowering shrub carrying on until early winter. Hardiness
wasn't an issue here since it can easily handle our very infrequent and
light frosts. It is fairly widespread in its native Brazil and is
largely tropical in origin where it can exceed 5 or 6m. In the UK it
can be grown against a wall in some southern counties, but needs
frost-free protection in most of the country. It's a wonderful thing
both in leaf and flower. I especially like it toward the end of the
growing year when the first chills of late autumn cause the older
leaves to turn a vibrant orange - very fetching in combination with its
silky purple flowers.