I snapped this photo yesterday with my telephone as I was playing in the garden with Sadie the Dog. If you aren't familiar with Tatarian Aster, it's one that you need to check out!
Aster tataricus, hardy zones 3 to 9
I got a tiny little clump of this baby a couple of years ago from a gardening friend, and now have enough to have split that original piece into six spots around the Stepchild Garden. It is definitely a strong plant, but not one that I would call invasive or a thug of any sort. It just hangs out in its original location, steadily growing into a larger clump. It separates beautifully and easily, so sharing is no problem at all.
The real appeal to me with this plant is that it is as close to maintenance free and I have found in the perennial bed. Seems to be just fine in wet years and dry, and is always neat and tidy. I have done NOTHING to this plant all season, and the stalks are all now about 4 feet tall and standing perfectly erect. No staking, no "Chelsea Chop," nothing. When frost finally gets it, I'll go through and cut back to the stalks to the base, and then it will do its thing for another year.
It is a late bloomer (some time shortly after Labor Day in Atlanta), so tuck it somewhere in the back of the bed. It just sort of hangs out looking well behaved and a strong green until August, and then it gets its growth spurt. Once it bursts into bloom, it is covered with butterflies and bees, and has a really beautiful clear lavender-blue color.