This pretty flower is a weed and one that we don’t want spreading. It is Epilobium hirsutum, Giant Willow-herb, and native to the Northern Hemisphere and grows to about 2m. There are native plants in this genus but they have much smaller flowers. It was noticed on a creekline in Buninyong. Looks like Ballarat Council needs to come out and get rid of it. They have been trying to control it for a few years but as you will see from the photos it produces a lot of small seeds.