Family: Lythraceae (Loosestrife family).
Native of Australia and southern Europe. There has been speculation that Small Loosestrife is non-native.
Occurrence: Widespread and common in damp places e.g. at the edge of lakes and streams, and in roadside depressions.
Photos 1,2,3: Small Loosestrife. Forest Creek. 4: Small Loosestrife in profusion. Bells Swamp.
Purple Loosestrife (Lythrum salicaria) is a much larger plant with showy flowers.