The Swan plant (Gomphocarpus fruticosus) is named for it's distinctive fruiting follicle which resembles a swan in outline. In Apocynaceae, toxic latex sap full of cardiac glycosides. It is a declared noxious weed in Western Australia.But a beloved darling of entomological enthusiasts because it is a host plant of the very attractive wanderer or monarch butterflies (Danaus plexippus and Danaus chrysippus ).
We encountered this weed in Perth's Hills recently, and I've noticed it along the Swan River at Maylands, although that population was quickly eliminated by teh local council (yes, I was surprised - but a local community group must have given them the heads-up).
Anyway - a quick study on this not unattractive plant, which is taking Perth's hills surburbs by storm (looking at you, Serpentine-Byford).