Heliopsis mid June to frost, Tunic Flower, mid June to frost, veronica (with deadheading) 2 months, Lilies, White Butterflies..4 weeks, and Scheherazade almost 4 weeks. Rudbeckia, Early Bird Gold is a new one which is supposed to start blooming earlier and bloom longer, it's day neutral. Time will tell if it lives up to the hype.

Rubeckia fulgida - Orange Coneflower (this the species rather then Goldsturn or other cultivars) starts in July and goes until frost.

Have Heliopsis - False Sunflower too - yes it starts in June & doesn't quit until Thanksgiving.

Red Milkweed - will keep going most of summer if kept deadheaded.

Japanese Anenome 'September Charm' - Once it starts in August it goes almost non stop for about two months.

Knockout Roses (technically a shrub) but starts in June and keeps going until frost.

Phlox paniculata - Garden Phlox - Begins in late July and with deadheading will keep going until October.

Clemtis 'Betty Corning' starts flowering in early July and goes to the end of August, sometimes even early December

Kautia Macedonica - Mid-Jul til first killing frost

Agastache (multiple varieties)
salvia greggii
salvia black & blue
echinacea 'Ruby Star'
KO roses
stick verbena (perennial for me)

Geranium 'Rozanne' or 'Jolly Bee' SUN
Heuchera 'Paris' PART SUN/SHADE
Heuchera 'Rave On' PART SUN/SHADE

All of these start flowering in late May for continue until October/November.

Hellebores and euphorbias for sure, but these are noted for retaining flowers for a long time rather than producing new over an extended period. Erysimum 'Bowles Mauve' is known for a very long bloom season - can be as long as 10 months in mild area but not hardy everywhere. Same with Lavandula stoechas 'Otto Quast'. Hardy fuchsias often bloom for me from June until December, if the weather cooperates. And I'd certainly agree with Geraniums 'Rozanne' and 'Jolly Bee'! Very long blooming and very reliable.

Salvia guarantica 'Black and Blue', Salvia 'Hot Lips', Dicleptera suberecta, clematis 'Petit Faucon' (just realize whether a clematis blooms a long time for you will depend on your zone as 'Betty Corning' blooms only intermittently for me after its original bloom cycle unless I cut it back hard after the 1st bloom flush), definitely verbena bonariensis, Kiss me over the Garden Gate (well probably more like hellobores and euphorbias as Pam pointed out which tend to hold their original flowers rather than rebloom).

I'll throw Helenium 'Mardi Gras' into the mix. It blooms mid-June through killing frost here in Omaha - I had a solid 4.5 months of bloom out of this plant

~Mike

Geranium 'Rozanne' part sun: blooms June until frost with cutting back mid summer to control spread

Shasta 'Becky' full sun: July to Aug.

Agastache 'Blue Fortune' full sun:July until frost with dead heading

Nepeta 'Walkers low' full sun: June and July, deadhead with some late summer to frost blooms

Persicaria polymorpha - about 2 months, with another month with fabulous seedheads
followed by Persicaria amplexicaulis 'Firetail' July to killing frost
and
Clematis 'Arabella' - mid June to killing frost

I have a white blooming verbena called "Snow Flurry" that is in bloom a good ten months of the year here in the deep south. I think it is available from Plant Delights, though it is a popular passalong in our area. If it's hardy in your area, I'd recommend it. Daylilies are incredibly long performers too, especially if you get a good mix of early, mid, and late season bloomers.

Clematis-many type 3s ie Rooguchi June to killing frost
Kalimeris incia 'Blue Star' June till end of August
echinacea-Fragrant Angel,White Swan,Coconut Lime,Tiki Torch and others end of June almost to killing frost
geranium-Tiny Monster and Ork-ney Cherry two dwarf sized geraniums that bloom all season.
Aster-Monch(sp) July till frost
An unknown Rudbeckia (very long saggy yellow petals fully double with clean foliage) June till frost
Veronica- with dead heading as mentioned one of them is June till frost

Sun:
Achillea x 'Coronation Gold'
Callirhoe involucrata (when I can keep deer snouts off of it)
Canna x generalis 'Bengal Tiger'
Delosperma 'Kelaidis'
Euphorbia corollata (again, deer food)
Gaillardia aristata 'Fanfare'
Kalimeris pifinnata
Lantana camara 'Miss Huff'
Nepeta x faassenii 'Walker's Low'
Rosa 'Carefree Delight'
Rosa 'Radrazz'
Salvia greggii
Salvia guarantica
Salvia microphylla
Salvia 'May Night'
Verbena bonariensis

Shade:
Corydalis 'Blackberry Wine'

Found the name of plant above it is Rudbeckia laciniata 'goldquelle' it's beautiful usually free of disease, light yellow double flower with nearly no cone. Grows and over winters well in average garden soil. Blooms from early July till well after frost. Last perennial blooming for me. I try to grow only very healthy perennials that can stand moisture because they are grown around roses which are seldom sprayed. Hope to hear more of others good plants. Pat

My Echinaceas bloom from Spring all the way till frost. Salvia also blooms for a long time.

It's not considered a perennial, but Diamond Frost Euphorbia is amazing and blooms longer than any other plant I've ever seen. It has blooms which are so dainty like baby's breath. I brought it in as a houseplant this winter and it's still blooming. I take cuttings of it every two weeks. I'm going to have it everywhere this spring!

Dahlias.....dahlias.......and dahlias.
Just wonderful for garden display and for picking.

The long-bloomers in my garden -

Buddleia
Scabiosa ochroleuca
Helenium 'Mardi Gras'
Rudbeckia hirta cultivars (short lived perennial)
Rudbeckia triloba

And the very longest bloomer, Dicentra eximia, native Bleeding Heart, which blooms from April-October.

I keep a record of bloom start dates, and weeks of bloom. By far the longest bloomer in my garden is Gaillardia ... all of them - Goblin, Burgundy, and Oranges & Lemons bloomed for more than 10 weeks straight. The second longest bloomers were Coreopsis 'Creme Brule' and 'Autumn Blush', which bloomed for 8 - 10 weeks. Third place goes to Echinacea which lasted about 8 weeks, though they looked pretty ratty towards the end. Oh, and there is one more that was in the 8 - 10 week range - Penstemon, both Penstemon pinifolius and Penstemon barbatus coccineus.

Bonnie

The longest blooming one I have is corydalis ochroleuca. Beautiful little tubular white flowers with foliage that resembles Bleeding Heart. Very delicate looking, but very hardy. When the snow melts, it's not unusual to see it green. It starts blooming mid-April until a hard frost. It's doesn't like the afternoon sun. Anywhere from 3 to 5 hrs of morning sun and it'll do fine. It doesn't like to dry out either, so I mulch it. I water it deeply once a week, and that's just fine unless it stays in the 90s for a week or more. Then I water it twice a week. It'll reseed and pop up in places you wouldn't think it would...but it's not invasive. The seedlings are easily pulled up. It grows about 12" high and at least as wide. It's a great filler plant.
My other long bloomer is geranium 'Jolly Bee'. Starts in mid June and goes to hard frost. I have mine in all morning sun with maybe 2 hrs of afternoon sun. Does great. It's a sprawling plant and fills in empty spots just great.

Kat

It is gaillardia for me. I think it may be the first to bloom and the last to stop. I do try to deadhead it now and then. I have two kinds, one short and one taller.

Salvia farinacea is another; not sure if it is a tender perennial or an annual but it self-seeds for me so I count it as a perennial. Blooms all summer and into fall.

I sure agree with many of the responses but don't see Nepeta Six Hills Giant yet. It's big plant, 4 feet, make a big clump. Ours starts to bloom in early July and keeps going until frost. It's a big time hummingbird attratctor. It can run like the dickens, though so I buried a five gallon pickle bucket with holes punched in the bottom. It stays put in there, grows like crazy and blooms its head off.
A specific clematis is the yellow bells of tangutica that doesn't stop once it starts in mid July.
Tom

I have noticed that Echinacea pallida blooms earlier than my other coneflowers. Plant it for earlier blooms. Tennessee coneflower blooms over and over for me. It's probably the best bloomer of all of them.

Mexican hat plant is a very tough, long blooming plant.

Red false yucca blooms last almost the entire summer. It was a favorite last year.

Asclepias tuberosa will bloom over and over. Simply cut it back to about 4 inches before the first blooms go to seeds.

Hydrangeas last forever here and you can dry the blooms and enjoy them for a long time. I did that this year.

Reading all of these comments is giving me great ideas for this summer. Thanks to you Daisy and all who responded!

Thank you one and all for telling me your favorite long bloomers, many of which I have already atarted from seeds indoors!

Here are some of my favorites that bloomed all last summer:

Rudbeckia Cherokee Sunset - many different colored double flowers (great cut flower too!)

Rudbeckia Summer Magic mix - pretty variety of gold, red and bronze flowers

Salvia May Night - pretty blue which bloomed a long time

Veronica Red Fox - pretty deep pink flowers which kept on going

Geranium - Max Frei and others

Heliopsis - Summer Sun & Smooth Ox-Eye kept blooming until frost

Gaillardia - Fan Fare got a lot of compliments on this one

Agastache Golden Jubille - my first year growing this and the foliage and contrasting flowers lit up the garden

I also loved all of my Heuchera and Sedum which looked pretty all of the time.

Daisy

Thanks for the Nepeta comments, YB; I don't have much blue-ish going on, and if it's a hummer-attracter, I'm all over it! And the tip on the bucket- excellent! Thanks again!

I don't understand why everybody else's Salvia 'May Night' blooms a looooong time but not mine. I have a beautiful flush of blooms in June, and then a few little blooms but it mostly goes to seed. Do you have to deadhead to get continual blooms?

I've got several other cultivars of Salvia nemorosa and pretty much avoid deadheading, dividing, transplanting, or weeding around any of them. Can't stand the smell of it! Ewww.

Salvia 'May Night'... had it for years and I only got one flush. Deadheading did not help. I ripped it out two years ago for something else.

'Butterfly blue' Scabiosa is the longest blooming perennial plant in my garden.

I agree with many of the suggestions here. Some others are:
- astrantia 'Moulin Rouge' - blooms for 2 months
- calamint - from August until frost
- variegated calamint - from late July until frost
- various scabiosas bloom all summer long
- delphinium 'Magic Fountains' - at least 3 weeks in June, and a reliable repeat blooming 3 weeks in September
- primrose - yellow heirloom - 2 months
- polygonum - Himalayan fleece flower - months and months. The light pink flowers age to dark rusty pink but are still very attractive

Also, as others have mentioned:
- coreopsis 'moonbeam' and 'creme brulee'
- verbena bonariensis
- nepeta
- dahlias
- knautia macedonica - from May to frost
- bleeding heart - both regular and fringed
- corydalis lutea - from May until frost

With regards to Salvia 'May Night', it does not bloom through the summer, but rather has two separate flushes of bloom. It starts blooming in May here and continues to the end of June. It's then cut back to the ground and a second flush of blooms forms by the end of August to frost. BTW, I've found that soil conditions make a big difference to the bloom of this plant. I have this planted in two different parts of the garden: one area is dry with very good drainage and the other has good drainage, but the soil is much richer and moister. I definitely get longer bloom from the same plant in the dry soil.

I get a light rebloom from May Night after cutting it it back. For me, Caradonna blooms much longer, with deadheading.Tom, I'll have to check out clematis tangutica.

For shade,geum rivale flowers non stop from aound may till the frosts,in sun potentilla monarchs velvet,geranium orion,geranium patricia and rudbeckia laciniata.

For me it's heucera-the old fashioned one.It starts in the early spring and is still going in the late fall. It's very long lived, the original given to me by a neighbor over 40 years ago. It's still where I planted it then.
Another long bloomer is primrose, there are 2 blooming now and they bloom off and on all year.

Flowergirl - What color are the flowers on you heuchera? That's a much longer bloom time than the heucheras I have. I wonder if someone could chime in here and guess what kind it would be. Have you been able to start new plants from seeds that bloom just as long? I would love to have some especially if hummingbirds like the flowers.

Sorry for straying off topic. My longest bloomers are salvias and the longest of those so far would be s. greggi 'Cherry Queen'. It's barely hardy for me and I'm just thrilled to see it return each spring.

Other long bloomers:

Salvia guaranitica, darcyi, & 'May Night',
purple poppy mallow
nepeta 'Walker's Low' and 'Six Hills Giant'
butterfly bush 'Pink Delight'
verbena bonariensis

The "old-fashioned" Heuchera that flowergirl refers to is likely H. sanguinea, often sold as H. sanguinea 'Splendens' or 'Firefly', although there are several other varieties.

These are relatively long-blooming in most areas, with a main flush in the late spring, and then sporadic bloom all summer and into fall.

As mentioned further above, I prefer the newer forms 'Rave On' and 'Paris'.

The flowers on my old timer coral bells are coral pink in color. Christie, if you would like a plant or two, I would be happy to send you some. No seeds, just plants. They spread on their own, I'm sure I've never had a seedling.

Flowergirl - That would be wonderful! I'll send you an email. I'm sure I can find you some plants to send you in return. Thanks - Christie

My coneflower did tremondous last year. It gets about 8 hours of sun a day and I was really surprised that it bloomed for as long as it did.

Great conversation! I didn't see Purslane- technically its not a perennial, but it does come back from seed = great ground cover, gorgeous flowers and whole plant is delicious in salads or by itself with a little balsamic vinegar. For ongoing perennials: I have five acres,so I'm limited on how many flowers I can keep that require "tending". I have an assortment of hedge roses that bloom spring through fall. Honeysuckle of several varieties. The kind of old fashioned orange daylily that naturalizes (don't know the name)- it blooms constantly too. Sunflowers, that I think came out of my feeding the birds (and some "mammoth sunflowers" - that have regular blooms but the plant is 12 ft high) = both bloom all summer through to frost.

Kautia Macedonia and Geranium Rozanne. I don't touch Rozanne but I do deadhead the Kautia. Both will flower from June to frost for me.