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Wollamai Point, northern shore of Lake Illawarra, New South Wales.

Wollamai Point, northern shore of Lake Illawarra, New South Wales.

Wollamai Point, northern shore of Lake Illawarra, New South Wales.

Wollamai Point, northern shore of Lake Illawarra, New South Wales.

Wollamai Point, northern shore of Lake Illawarra, New South Wales.

This is just about the worst groundlayer weed of this patch of littoral rainforest. It is very shade tolerant and spreads amazingly fast after good rains, though only vegetatively. In fact, I doubt that it's known to set seed in Australia - I have never seen a seedling.