Catmint is my absolute favorite tough, long-blooming plant. Needs almost no water, and once it starts blooming in mid summer it keeps going right until frost. It doesn't creep, but it does continue to increase in size, so it will either need a really big area or you'll need to split it once a year.

The only thing to watch for: bees LOVE this plant. That doesn't bother me - I've found I can cut this plant to the ground even when it's covered with bees if I move carefully - but maybe it should go in the back of a public garden.

Sorry, Jan, forgot to specify - part to full sun for catmint.

My longest blooming plant this year was Salvia. I'm not sure the variety. (Is there anything such as a standard salvia, tall with purple flowers? ;)

It seemed like it bloomed all the way from June and ending only in the 2nd week of October when we had a killing freeze (it survived a number of frosts before succumbing to the freeze). Bees and butterflies love it, too!

Mine was growing in full sun. It can definitely survive with less watering.

Yesterday as I was working in my garden I noted the long blooming period of gallardia 'Burgundy' which is still in full bloom and putting out new blossoms. Mine is planted by the mailbox in full sun and survives with little more than rainfall.

Guara is another that continues to bloom for me.

My Favorite Yellow Quill mum starts blooming midsummer and continues through light frosts.

Annual alyssum is still in full bloom after two light frosts.

Others to consider: echinacea, rudbeckia, delphiniums (second bloom when cut back after first blooms), some shasta daisies, upright sedums, clematis, campanula Blue Clips, White Clips, alchimilla, Heliopsis 'Summer Sun', lobelia siphilitica 'Great Blue', hellenium, veronica, salvia (both annual and perennial), melapodium, gomphrena, buddleia, penstemon 'Cambridge' (blooms all summer for me & is perennial, short and compact).

All grow in my gardens in either full sun or part sun with limited supplemental watering.

Are you looking for perennials or annuals. My garden club plants several beds each year. The median bed is always planted with annuals. This year in the median bed we used cleome Senorita Rosalita, Profusion yellow zinnia and Vista Bubblegum petunia. We had great comments. We've used Vista Bubblegum several times now always with stellar results. All three of these plants bloomed all summer with no deadheading and only occasional watering after the first couple of weeks getting established. IMHO Vista Bubblegum petunia is one of the best petunias the plant breeders have come up with in years.

I second the Vista Bubblegum recommendation. It has become my favorite petuntia for my large containers. Angelonia is another great long blooming annual. Profusion zinnias and Zahara zinnias are long bloomers and powdery mildew resistant.

Bergenia cordifolia is the longest blooming plant in my garden. It grows in shade, part sun and sun. I have seen it is a evergreen and I have seen it blooming before the snow is all gone and it is still blooming today, Nov 1. I love it. It also spreads a lot.

Thanks for the thumbs up on the "bubblegum"
I just thought of Bergenia this week. I know it spreads, but will it kill other plants? It is beautiful, tho I haven't seen it bloom. Definitely Angelonia, Walker's Low catmint and May Night salvia . Is the yellow quill long lasting or would yarrow be more so. You have intrigued me with Profusion zinnias and Zahara zinnias - long bloomers and powdery mildew resistant. Good to know, I love zinnias.
grammajan

zenpotter, is there a certain variety of Bergenia you are growing that blooms for that long or do you have it in full sun? I love my bergenia but none of them blooms all summer. One variety blooms in the spring and is blooming again now but the other only blooms in the spring.