I started out with the best intentions with several of these....due to Life taking me down some bumpy roads once I put them in the ground, I didn't follow through much, other than to occasionally put the sprinkler on them.
Let me back up a bit. I planted them in our very poor, compacted, but sandy soil, under the fringe edge of a mature Box Elder. I did amend the soil with some decent garden soil, and some green sand. They are on the south side of a border fence and get a lot of snow cover, because that is where I shovel it to while making runs for my dogs in winter.
I am in zone 3, and they have performed absolutely wonderfully for the haphazard care I have given them. Mine are about 6 or 7 years old now, and have reached a height of at least 6 feet. The form isn't the best due to my lack of pruning, but it's not bad either all on it's own. And the flower heads are truly spectacular this year, despite a really crummy harsh winter. They are absolutely a sea of LARGE flower heads. 3 of them will fill a vase. 5 is opulent. I've been giving away bouquets to neighbors, who are extremely impressed by my largesse. Hah -- little do they know I'm just thinning the herd a bit, and trimming them out to ensure even MORE blooms next year!!
These are spectacular, gorgeous, and dry well too. They are one of my favourites, and my Gramma would be proud to see these.