Interesting question, but "good growers (vs. slow growers)" and "without demanding a lot of extra care" does leave a lot to personal interpretation.

From my experience, I agree with Helenium 'Rubinswerg' and Aster x frikartii 'Mönch' not requiring a lot of attention. The former is longer lived (e.g. lasts more than five years in our growing conditions). Both are clump-forming and the clumps seem to expand quite slowly. In our mixed perennial beds, I'd take that as a positive.

Have tried a number of Gaura lindheimeri cultivars, but none survived the winter in our own garden. On the other hand, I've seen Gaura overwinter in another garden in our neighbourhood.

I'm very fond of Pardancanda. I have a fairly large planting of them near some Echinacea and the summer combo is great. I do wish they bloomed a little longer. But also appealing are the sword-like leaves which, unlike those of bearded iris, stay handsome looking throughout the season. Very low care, though I do cut them back after bloom because, though the seed heads are very interesting, I simply cannot deal with all the reseeding.

I am big on perennials that do not need watering (slow and steady wins the race in my garden). I love HERBS (especially rosemary, lavender, sage and thyme), ornamental grasses (especially the smaller less domineering ones), prickly pears (Opuntia humifusa), and Russian Sage.

I too like very much frikartii Monch. For the first time I trimmed it back earlier this summer to minimize its flop. It is just starting to bloom for me now.

Marlorena, I love that picture of 'orientale'.

rouge..thanks.. .. I love Pennisetum's although I know they're not that hardy in northern zones...

...fortunately my 'Monch' doesn't flop... but I think I'm right in saying that there are a number of clones doing the rounds that masquerade as 'Monch' that do flop.... so we never know which we've got until they grow...

laceyvail, I've never heard of 'Pardancanda', so I got to go look that up...