Arctotheca calendula Cape Weed
This introduction from the Cape of Good Hope in South Africa was first noticed around Albany in the early 19th century and since then has spread all over western Australia. It has been used as a fodder plant which explains why you can see acres and acres of yellow flowers extending on the horizon in some parts of W.A. on the coast road to Geraldton from Perth.
It is also sometimes known as the Cape Dandelion.