Nancy, I know exactly where you're at in deciding on whether to plant a particular perennial or not.
I tend to be a bit of a perfectionist myself (OCD!) in "policing ?" perennial beds: always aiming for blocks of colour.
As many of us would likely say, be very careful of buying perennials from places like garden club plant sales. Why some of those perennials got to be there, for sale, is exactly because they're vigorous seeders or runners. Personally, for me, the main attraction of (more expensive) cultivars, compared with species (wild tyes), is often that they're more tame (well behaved) in perennial bed. And, I aim for the beds to contain enough of a diversity of different perennials for ongoing flower colour, throughout the growing season.
Then, of course, the same perennial can behave differently, in different growing conditions, within the same garden!
It may be reasonable advice to try a certain perennial in your garden; but that goes with keeping a very close eye on it, so that there'll still be time to eliminate it, if necessary.
Vic, you know me; I garden for flower colours. Love colours/colors (latter, my friend, as you'd say!)
