Helianthus is a sunflower - they are beautiful!
I've never seen one. Do they grow tall?
I think so, and they are native to north America.
I think I've eaten the seeds in the past. 
The common sunflower is also "Helianthus annuus"
Funny name. You know a lot of about them. Do you have a flower garden?
No, unfortunately. And perennial sunflowers are usually not suggested for gardens.
Why not? That's strange.