If you are looking to make a statement in yellow then you should consider Rudbeckia.
I planted three small pieces from the house yard into the rows last Autumn. I had to tie it up just a few weeks ago as it was flopping all over the place. It flowered two weeks ago and still looks good after a weekend of wind and rain. It is hard to show just how tall they are without a person in the shot but I estimate them at 10 ft tall (3.5 metres just doesn't have the same ring to it.)
The Zinnias are dwarfed by the Rudbeckia stand.
This next plant is a Cherry Rudbeckia. This is the first time I have grown it and I am surprised at how different it is. I have had just one spectacular flower on a very short stem. Our summer was very mild so it is hard to know what it could have become with a little bit of warmth and all the rain.
There has been a population explosion of pumpkin beetles.
I am going to get my gloves on for a squashathon .