As I neared Miles (Queensland) I was impressed to see fields of purple flowers (purple is my favourite colour), though I knew not what they were until I spoke with folk at Miles.
They are not native to Australia, and sadly have run amok around the west of Brisbane. Along the side of the roads, there are purple patches of these flowers. They go for hundreds of kilometers. The local folk get angry that in the city, these plants are for sale - giving further opportunity for them to be seeded and sent further into places where they are not wanted.