I do grow them, but did not get them from MB. The first year they grew about 4-6 ft with a few flowers. The second year, in the gound, mine were over 12 feet tall and just covered with flowers. The third year, I had a few in a five gallon bucket (I had moved) and they still got about 8 ft tall. I just had to water them a little more. They reseed for me. I love mine and hope to never be without them (-:

I don't have that one but have a perennial sunflower I've always thot was a heliopsis which is quite similar to the helianthus. Also called False Sunflower. Mine is multi-petalled. It was a plant I got years ago from a fellow garden club member and has been very reliable in this climate. Grows like a weed and self seeds but is not invasive.

I made the mistake of planting them at the back of the border next to the horse pasture and the horses easily reached over the fence for the tasty snack! LOL After trimming the plants they came back very well and an electric line prevented a recurrence.

This pic and the following close-up show the plant. Last fall they didn't get trimmed back so I should have lots of volunteers - will have lots of plants to give away this year.

Here is a link that might be useful: my perennial sunflowers

I plan on planting more sunflowers this year, too; wasn't aware that there were perennial varieties or that some seeded down. I like the tall ones, but not with multiple flower heads on one stalk.