I've only grown one sunflower this year, and that was an accident. It's sprouted, incongruously, in a tiny hanging pot which I had planted with a Crazytunia and Sweetunia (the crazy outcompeted the sweeties, though that may have been down to position rather than vigour) and has a teeny tiny protoflower. A+ for effort; in my usual way I've not done any removal. I reuse old potting compost (OMG diseases trumped by continuation of biome - which in so many ways are essntially the same thing) so a seed probably went in in that. I have lots of sunflower seeds, most from the first glorious year of sunflowers, before I put in the fennel and the raspberries and the sunflowers had the fertility hotspot all to themselves. Lots of other people have planted sunflowers this year, though (there are some lovely giants right in the my street!) including my local park:
Water and temperature stress (and everything has been stressed this year, whether they like it warm, cold, hot, wet, dry or mild) makes for interesting variety in the mutable petals of the sunflowers. I especially like the ones which show little green flashes of sepal above their petals. But of course you can't order that.