We are in Queenstown and this plant has proliferated throughout our garden.
Lanceolate leaves; 6 concentrically around the stem when young then seem to move into opposite pairs. Leaves found the length of the stem. Grows to about 1.5m on spindly, hollow stem with late season small purple bell like flowers pointing downwards. Either self-seeds or via rhizome, but has spread a lot in just one season. Have searched our library, local gardeners and websites but I'm stumped!!