I too planted some tubers this year about 4 of them, I am in zone 6/7 mine are about 8 feet tall also but no flowers, it looks like they have flower heads forming. They form these tubers to survive the winter so they have some time before harvest. I had not planned to harvest mine until they die back. If you harvest as much as the tubers as you can even if you miss a few next year you may have a plant or two. I don't think they will take over the garden bed as quickly as you may be thinking. If you don't harvest the tubers then you may have more than you want next year. I planted them because it's a good source of food that is preserved on its own in the ground and as long as the ground is not frozen you can harvest as needed.

Good luck and I will be interested in what others have to say as I too am new to growing these.

Jerusalem Artichokes essentially grow themselves. You need do nothing at all as long as they have sufficient moisture. The lack of flowers is irrelevant. Mine have never flowered. It's the tubers which matter and they are totally hardy. When the stems die back you can cut them down and add to the compost heap but leave a bit sticking out of the ground so you know where the tubers are. You can dig them at any time if you can get a fork into the ground.

I think it is too early to harvest now. If you are in a place that had little rain this summer that may be the problem, well unless you have been watering them. I think they are running late for blossoms this year.

They will grow in heavy brush area if you want to move them or let them go wild. Or you can put them in a pot but the roots will come out. Cut the blossoms off before they go to seed if you don't want them to spread.

I have them growing wild all over on my property...mine do flower. I haven't done anything to grow them, they are basically weeds with benefits...I am wondering, though, because they are perennials if they need a few years to get established? Most perennials do. I dig them after a couple of hard frosts, and i put the small tubers back in the ground. I have them in many spots so I never dig the same spot more than once every 3 or 4 years.

Donna that's a good point, not sure if they need a few years to develop larger tubers. Mine were about the size of two golf balls side by side when I planted them, I planted 4 of them. I will have to remember to harvest and take a pic to show if they did well for me year one. I do plan on leaving some for next year.