Hi, This is my take about this. I think you will find that the Japanese sunflower and the Mexican sunflower you see growing wild sometimes along road sides are classed as obnoxious weeds.
Not trying to be a spoilt sport, but like already stated, Sunflowers are not native to Australia and Sunflower seeds are high in fat and are basically not recommended as a natural diet for Australian native parrots except as an occasional treat in spite of seeing them in those wild bird mixes you buy. They are a high heat fuel source, can overheat their bodies thus affect their feathering, can be addictive and cause some birds endless health problems like obesity.
The domestic type Sunflowers you see in people's gardens have high cultivation needs and don't take well to growing wild. The birds will often rip the seeds out from the ground before the plants get a chance to grow anyway.
I've worked with Australian endangered flora and my thinking is that if one is to plant something, that is, if it is legal to do so on public land, maybe a yellow flowering (I gather Allison loved yellow flowers), native plant suitable to the local area and one which is of a species that the local native wildlife feed from and rely on for their well being.
Some seed mixes contain large quantities of sunflower seeds, which may attract larger seed-eating (granivorous) birds (particularly parrots), but these seeds are high in fat. Black sunflower seeds should be avoided altogether; a small quantity of grey-striped sunflower seeds is fine. (The detrimental effects of high fat diets on bird health are similar to those for us unfeathered creatures).
http://www.brisbanebirdvet.com.au/LinkClick.aspx?fileticket=G83tQP4QcPA=&tabid=21642&mid=13254
).. ( And you only need a little bit of water to drown.)
