Epilobium tetragonum

Epilobium tetragonum, commonly known as the square stalked willow herb, is a species of flowering plant in the willowherb family Onagraceae.
The erect perennial herb typically grows to a height of and can have several stems. It blooms between January and November and produces pink-purple flowers.
The species has become naturalised in the Perth and Peel regions of Western Australia.