A Towering Flower

Hello! I am 5'3", which isn't that tall for an adult. However, I'd consider a flower that height or taller to be pretty tall. 

For example, the Joe Pye Weed (Eupatorium maculatum 'Gateway') I have growing in my backyard:

I bought this plant as a young perennial several years ago at a local nature center's plant sale. The accompanying tag said that it could be planted in either sun or partial sun. I have more of the latter than the former in my yard, so I figured this plant would work for me. It was supposed to grow to the 5'-6'range and would have "enormous, fragrant flower clusters up to 18" across" that attract butterflies. Sounded good to me! 

I brought the Joe Pye Weed plant home and placed it alongside the neighbor's fence. It grew fine for several years, but never got any taller than 4' high.  Didn't get much bigger around either, and I didn't get those enormous flower clusters. I was disappointed and thought perhaps I hadn't sited it well. I considered moving it to another part of the yard but didn't do so.

Then last year, for no apparent reason, it dramatically increased in height and spread, and did the same this year. It is now around 7' in height, and has spread enough that I occasionally cut some of its stems just so I can walk through that part of the yard without feeling I'm in a jungle. 
 
These stems, cut further down, made for a nice arrangement in a vase along with some rudbeckia:

May not look like much, but the vase itself is over a foot tall. The height of the tallest stem is over 2' tall. This arrangement is now adding some flower power to our dining room. 

I'm glad I hadn't gotten around to moving my plant to another spot, as it's obvious now that it's quite happy where it is! Guess I just needed some patience to let it do its thing.