Yup, hibiscus alright. Not to be confused with the Oyama magnolia. Invasive plants often (not always but often) start as escapees from someone's garden, and with no natural predators it takes over ground and crowds out native plants. Victoria is up to its armpits in ENGLISH ivy, HIMALAYAN blackberry SCOTCH broom (actually from Egypt) and JAPANESE spurge, to name a few.
Mike.