Hibiscus richardsonii (Flower-of-an-Hour)

Description and photo in: Craven, L.A., de Lange, P.J., Lally, T.R., Murray, B.G. & Johnson, S.B., (2011) A taxonomic re-evaluation of Hibiscus trionum (Malvaceae) in Australasia. New Zealand Journal of Botany 49(1): 30-34, Figs 1A, 2A, 3.

It can be distinguished from the introduced H, trionum (a potential garden escapee) by the flower having only small purple patches at the base of the petal, not large ones.  Found in near-coastal locations from NSW north coast to Tathra, and possibly proliferating after disturbance.