Coreopsis 'Zagreb' has been very vigorous for me, and at times a little too vigorous. It would definitely naturalize if allowed. Deadheading doesn't seem to make that much of a difference.
After two years, Coreopsis 'Moonbeam' has disappeared from every spot in the garden. It's a mystery.
Crystalview, this article about coreopsis research at Mt. Cuba Center was specifically for the Mid-Atlantic region, but you might find some of this information helpful.
http://www.mtcubacenter.org/im...
