Because our season begins in February there are few perennials left come late summer. So the answer for me is the annuals, particularly a single red tall cutting zinnia I get from Renee's Garden. Perennials I do have that keep the show going are the salvias that bloom most of the year, agastaches that likewise have a long bloom, the alstromeria that comes back happy once the heat slows down, and mums, if I am faithful to keep cutting back clear into August. I took out Japanese anemone Honorine Jobert because it spread too much and never really looked good and does not cut well. I have been adding: aster Purple Dome, which I loved but accidently chopped off, eupatorium chocolate which has off-white fuzzy flower heads, Kirengshoma (sp?) which hasn't bloomed yet but should have soft yellow bells, filipendula, a hosta, dictamnus and maybe some I am forgetting. Phlox blooms right on through as well.

Zebrina malva ,Autumn Joy sedum, Fall Asters,

I love native plants for late blooming summer perennials!
Tall native sunflowers come in several varieties. Maximillian isn't quite as tall, there are the willow leaf types and so many others. There are also many types of ironweed, the above mentioned asters, hardy chrysanthemums (dentranthemum as the names are changing again), and of course so many beautiful types of native and hybridized native solidago. There are also solidasters, helenium, salvia greggi and relatives which seem to get a 2nd wind...and frankly my brugmansias look the best in the fall, which is why I decided to plant oranges/yellows since they look so pretty with the other fall colors in the garden.

GGG

Boltonia is a lovely late summer/fall bloomer. I also like Eupatorium 'Chocolate', perennial anemones, purple coneflower, sedum Autumn Joy, ornamental grasses and annual zinnias for fall color.

Yep - Dahlias steal the show in late summer and fall. I dig them up and replant them every year- but it is worth it. I also do Cannas- they are also tall and mighty by august ad september!

My hardy perennials though- you gotta have mums, aster, and i just got Montawk Daisy. Like a shasta only more liek a mum and blooms in fall! I also have a perrenial called "Turtle head" and it is fabulous. Never gets disease or any problems with bugs and it blooms pink flower that are shaped liek a turtle head. the foliage is very dark green too. I need to work on my arrangement so that there is fall stuff through the gardens though.

Usually my coneflowers ( pink/purple) keep going too if you are deadheading them.. but i leave them for seed for the goldfinches.

I think nobody has mentioned naked ladies yet. They bloom for me in September and are a lovely addition to a late Summer/early Fall garden. I also do Joe Pye Weed, mums, Autumn Joy sedum, as the others suggested. However, Fall for me is the riot of foliage and berries - I absolutley love them. Can't beat firethorn for a Fall look, loaded with red or orange berries, as well as beautyberry (callicarpa) paired with naked ladies and smoke bush - the ultimate Fall combo, IMO. Japanese maples with viburnum opulus and mahonia is another winning combination for me. For window boxes and containers, mums and coleus work the best. For those with enough room for the vine, ornamental pumpkins are also a great addition. And a couple of deciduous trees with good Fall color. This will vary according to your climate, but in mine the best colors come from the sweetgum.

Eduarda

I'll definitely second the dahlia recommendation. Mine bloomed well into November, after several frosts here in zone 5, which was amazing.

Also, my cosmos,snapdragons, and marigolds kept going all season long.

For perennials, I had the best luck with guara "Siskiyou Pink," mums, salvia "May Nights," and veronica "Goodness Grows." Of course our climates are different, so I'm not sure how these would work for you.

Tracy

My season starts around March 15. My late summer workhorses are abelia, blanketflower and mossy verbena. I also rely heavily on rainflowers, salvias and miniature roses. I cut back the blanketflower and verbena at least twice during the season and they will carry on into fall without a problem. Abelia and mini roses take at least two to three seasons to really get established, then they pretty much bloom from April through late fall. If you like zinnias I would suggest Persian Carpet, much smaller than the modern cutting zinnias but the colors mix well with the summer borders we have here in the south. Pinetree and JL Hudson both carry seed.

Caryopteris holds off until August in my garden and attracts butterflies by the hundreds. Mine is planted between two Montauk Daisies (aka Nippon Daisies). The caryopteris is just winding down as the daisies take over. For anyone who's not grown this plant...it's wonderful! It's a sub-shrub (like lavender gaura, Russian sage, etc.) and grows to a 4'x4' globe with thick foliage/stems...almost like a succulent. I prune mine down twice/season and it is always covered with hundreds of 3-4" white daisies Labor Day through Halloween.

Also, hardy hibiscus will bloom well into late September...early October here. Sedums have faded by mid-August but still I leave the flower heads standing because I think they're attractive in their own right.

I rely heavily on berry producing shrubs, foliage, & ornamental grasses for late season color. By mid-September to early October...my perennials are winding down...and so is their gardener!

Tracy,

Glad you mentioned cosmos. I haven't grown them in a while and wondered if I should set some out now (they're fast growers here).

Anne

for annuals - cosmos, sunflowers, snaps, zinnias

for perennials - Clematis tangutica (gorgeous!), rudbeckia

for shrubs - hydrangeas, Blanc Double de Coubert rose - pure white, very hardy rugosa that blooms continually here from early May until November, which is a feat in Canadian zone 4B/5A!

Dahlias, asters, and fuchsias are my favorite fall bloomers. I like upright small-flowered hardy fuchsias (hardy here in zone 8 anyway), and they bloom non-stop from mid-summer until frost. Hummingbirds like them too, and also Cape Fuchsias, Phygelius, though I am down on them some as most died out on me after a few years. Some roses are reliable in fall, like Marie Pavie and Zepherine Drouhin, for me anyway.

My favorite fall bloomer is pineapple sage. I think it would grow in zone 9.

Color wise, Dahlias and Cannas definitely. Sedum and Asters, as common as they are, are pretty darn reliable as well.
The real stars for late summer/early fall/winter are my ornamental grasses. My garden becomes a total riot of grassy plumage(word?) this time of year. Great for interest and structure all the way into late winter.

DAhlias, yes, and aconitum! Otherwise known as monkshood, it is one of my favorite things in the garden- I wait for it every year. It is poisonous which deters some people but so is digitalis and anenomes. Gorgeous blue.

Toadlilies (Tricyrtis), hardy plumbago (electric blue flowers well into fall), solidagos, Japanese and hybrid anemones, Helenium, any of the salvias, hardy or otherwise. And a second on the hardy fuchsias if available and truly hardy for your area. These will keep pushing a profusion of blooms well into fall and in milder climates, often into winter as well.

If deadheaded, many of the common prairie flowers will keep producing until late season - heliopsis, coreopsis, echinaceas and rudbeckias, oenothera.

Thank you for all the wonderful ideas. I'm looking forward to planting many of these in my garden.

Don't forget the annual vines! Mina lobata (the name has changed, but you'll still find it under this) is a fabulous annual fall blooming vine. Ipomoea quamoclit and it's close relatives are lovely as well. I love the wildly flamboyant florists chrysanthemums (Dendra..something now) I get from King's Mums each spring. They bloom from August or September clear into December in my mild climate. Caryopteris is great for the bees and I really like Japanese anemones, probably because my mother grew them when I was a child, but they also look nice and I just pull up the starts.