I just bought a Helianthus called 'Happy Days.' It says it's hardy to Zone 9. I'm trying to find out what kind of light exposure to give it in my area. The tag says full sun, but I know some plants can't take the heat here. Those plant tags don't always have good info on them .I've never grown a perennial sunflower before. If this works out, I will be growing more. Does anyone know anything about growing these plants in the south. I'm in zone 7b in West Tennessee. Any tips would be greatly appreciated!