Coreopsis "Jethro Tull"
Penstemon "Dark Towers"
Penstemon "Mystica"
Amsonia "Blue Ice"

A nearly infinite list of plants could be generated by your question, especially in lovely zone 7. Most plants will increase their size in some way. As a general rule, though, plants to avoid are those that produce runners or copious amounts of seeds. Do you have a bloom color preference? Height preference? Any issues with drainage, rabbits, deer? Do you prefer fragrant flowers? With the number of plants that fit your initial request, you can afford to be much more specific.

I might recommend getting your own personal copy of "the bible" - The Well-Tended Perennial Garden by Track DiSabato-Aust, or at least check it out of your library. My other favorite book is Botanica's Annuals & Perennials. This is the most comprehensive list of flowering (2,000) plants I've ever seen, with pictures of most.

In the past, I've never had the results I wanted by starting my planning with the question "what do I want?" The chances of finding those particular plants in a store near you are not always good. Lots of people do it, but I'm not comfortable ordering plants from faraway places by mail or internet. So I find it's best to shop around, see what's available, then decide "which of these plants do I like?" From there, you can determine which of those would perform to your satisfaction in your garden.

Well, I guess that was a rather open-ended question. What I meant was that I want only groups of individual plants like astilbe or mums and it is difficult to tell that from plant descriptions in catalogs. For some reason, they don't like to say "invasive", LOL!

I seem to have bad luck and end up with perennials that want to spread all over the garden I had to dig up all the Knautia last year because of self-seeding up to 10' away. I am going to dig up the Teucrium because it just keeps creepin over its neighbors. The Salvia Purple Knockout ends up everywhere (and in the lawn). The last straw was the Lysimachia Firecracker I received mislabelled as Coreopsis Golden Gain and is now threatening to take over my garden.

So I thought suggestions of nice polite perennials from people who have them seemed like a good idea.

Basically, my garden has (of the polite plants) Coneflower, Astilbe, Stella D'Oro, Aquilegia, Trollius, Autumn Joy Sedum, Veronica, Stokesia, Aster, Mum, Hostas, Ferns, Heuchera, Liatris, and Oriental Daylilies.

Any other types I should explore?

You're talking yourself through your own answer (smiles!) Almost anything suggested as a ground cover, anything "creeping" and heavy seed producers are going to displease you. Here's a few to consider...

Delphinium
Iris
bulbs for earlier
Baptisia
Thalictrum
Brunnera
Bergenia
Polemonium
Dianthus (will spread politely)
Creeping Phlox (will spread politely)
some of the fragrant, tall garden Phlox (selection varies by geographical area)

Any interest in bigger plants like roses, peony, beauty berry, hydrangea, butterfly bushes? All extremely polite, non-fussy residents.

Sorry, I should have mentioned shrubs. The background is butterfly bushes, nandina, euonymous, and spring flowering almond shrub.

And I forgot the baptisia, which make a great backdrop to the deck. But the others, those are suggestions I will look up. And THANK YOU so much for them!

I'd like to warn you : Polemonium caeruleum is a terrible seeder. You will regret it bitterly. Tall garden phloxes do not stay put. Many varieties send runners, David being the worst of all. Brunnera is a seeder as well as Thalictrum, especially aquilegifolium, but you can cut the spent flower stalks of.

Well, folks, if you don't want plants to reseed, don't let them!!! Just cut them back before the seed is set. It's simple and it's what gardeners do! It's called tending your garden.

Basically I agree with laceyvail. But in cases like Polemonium caeruleum or Tradescantia it would be too much work. It would involve removing individual flowers, and I don't think they are worth the trouble.