Whilst Sweet Pittosporum (Pittosporum undulatum) is a native to Australia, it’s considered by most to be a weed in the Dandenongs.
In the last few years I’ve been associated with a site in the Dandenongs where someone has been working at getting rid of Sweet Pittosporum on his property.
It’s been a long, hard, expensive, leech infested slog but improvement is possible. If it’s worth doing you need to stick it out for the long term. The area in the photograph below was suffering from Sweet Pittosporum.