Salvia uliginosa bloom longer in my garden than just about anything else. Calamint is a close second with catmint probably in third. Salvia guaranitica bloome pretty much constantly once it reaches blooming height, but that can take a few weeks. Still, it blooms right through from midsummer until cold weather, which is when I bring it in.

Cannas bloomed all season for me last year, too, but I dig those up - I don't actually know whether they'd last the winter out there or not.

Roses bloom longest for me....or are they a shrub?
Linda C

Gaillardia 'Goblin' bloomed here from mid-May until the first hard frost. It loves full sun, and is drought tolerant.

Bonnie

Geranium "Jolly Bee" was my longest bloomer last year beginning in late May and ending in late September.

Ozark primrose (Oenothera missouriensis) is another very long bloomer. A nice trailing habit with poppy type large yellow flowers.

Nepeta subsessillisis was colorful from early June till Setpember. A lot of intrest in the bloom from the bees, butterflies, and hummingbirds. The goldfinches then came for the seeds in the fall.

Verbena Homestead Purple. It's supposed to be treated as an annual here, but has returned for it's fourth season. Began to bloom this week and will continue until hard frost. Love it!

Penstemon blooms nearly year round here; hardy fuchsia blooms from August to December; and erica (heath) blooms from late December to late April or May.

I'm not sure that is helpful to folks in other climates, but I really treasure these plants that work so hard for me.

Geranium Roxanne - it never stops.

Purple coneflowers and joe pye weed don't start blooming until late June or so, but they last until fall. And the foliage gives substance, too. Also, my coreopsis verticilata...species and cultivars have a long bloom time. The balloon flowers, too.

gaillardia,scabious(pincushion flower),balloon flower can go 10 months in here...love em.

For me,the longest bloomer is verbena 'snowflurry'. It starts blooming with the daffodils and does not stop, even with a hard frost. It will bloom off and on during the winter when night temps stay above the mid-twenties. I live in zone 6. Amazing plant! Plus it comes true from seed. It does not spread like 'Homestead Purple' and gets a little taller.

Here is a link that might be useful: picture of verbena 'Snowflurry'

For me, it's may night as well as anise hyssop, catmint, balloon flower, my shrub roses, shastas, daylilies, speedwells, liatrus, coneflowers, gallardia, sedum, phlox, chrysanthumums, and more that I planted in the fall and I'm waiting to see how they perform this year. There are alot of good choices out there to try. Have fun with it.

Geranium 'Jolly Bee' here as well. It got to the point where I got a little tired of it! That and my knockout rose were still blooming up to the first frost.

farmerbell..thanks for the info on Snowflurry. I've stayed away from verbenas since Homestead Purple took over my yard 5 or 6 years ago. I was ripping it out by the wheelbarrow and hesitant to try another one, but I'd like to try this one. Also I think white might be a little easier to work with.

The following plants bloom for more than two months:

Achillea 'Coronation Gold'
Euphorbia corollata
Allium senescens var. calcareum (Blooms late May-mid July, takes a short rest and then blooms again Late Aug-Sept)
Perovskia x atriplicifolia 'Longin'
Salvia greggi 'Cherry Queen'
Salvia microphylla 'Wild Watermelon'
Salvia x 'Maraschino'
Stokesia laevis 'Peachey'
Verbena bonariensis

The very best are Alstromeria, then Penstemon, then Salvia.

I've a geranium in a pot that has has continuous bloom for about three years. Sometimes it gets a ugly and I clip them all off but left to its own it seems it would bloom continuously.

We a rose of some sort that blooms from may until frost.

Salvia microphylla "Hot Lips".

salvia 'purple rain', rose campion, scabiosa, jasione, corydalis lutea, calamint

I will have to try that white verbena, I never heard of it but it's lovely.

Scabiosa is the longest blooming for me.

It's got to be scabiosa ochroleuca for me. Rose campion does ok too.

1. Gaillardia
2. Purple perennial Verbena

moonbeam correopsis
and of course, my roses.
some clematis rebloom from June through to fall.

Clematis Ville De Lyon. Starts blooming in late June and goes heavy on the flowering straight into September.

Rudbeckias -Gloriosa Daisies. Can't beat them. They keep going from July until frost.

Verbena Bonariensis - Minimum 2 months bloom and the butterflies are a bonus!

Scabiosa ochroleuca was a very long bloomer last summer - and I didn't even deadhead because the Goldfinches love the seeds!

Winter-sowed lots of cultivars of Rudbeckia hirta this year, so I'm looking forward to those blooms.

Knautia macedonica starts in May and goes through Fall
Geranium Rozanne
Clematis Betty Corning and Polish Spirit are my longest bloomers.

To all you verbena people,

How do you keep your verbena alive over winter? Mine just die in the garden. I have tried various times with various varieties.. They just don't make it.

Do you plant them in sand for extra drainage?

Don't cut back the verbena at all until spring/last frost and don't water it during the dormant season. I had a beautiful pink and white verbena come back this year because it was sheltered under a lavender. I definitely thought it would be annual.
But we had a very mild winter too.

Lantana, Snowflurry verbena (it seeds around too, without being a pest. Great plant!), Salvia guarantica Black and Blue, Salvia farinacea Mystic Spires, Tibouchina (takes a while to get going), nothing blooms longer than (the right) roses, butterfly weed, cannas, Gulfcoast penstemon.

Scabiosa
Nepeta 'Walker's Low' and 'Six Hills Giant'
Verbena bonariensis
Homestead Verbena
Perennial heliotrope 'Azure skies'
Salvia greggii 'Navajo Red'
Delosperma cooperii

My snapdragons are perennials here, but annuals other places. They bloom forever it seems.

Cameron

My heliopsis "summer sun" is one of the first to bloom in my garden and goes ALL summer

Modern Roses
Veronica "Sunny Border Blue"
Nepeta
Russian Sage
Verbena Bon.
Coreopsis Vert. "Moonbeam"
***
Dianthus Int. "Ideal" or "Bouquet"
***
Gaura "Siskuyu Pink"

Only the first category are really perennials. The Dianthus hybrids are theoretically annuals, but keep coming back for me. But then the Gaura is supposed to be a perennial, but blooms like an annual - and dies out in winter like on too!
I only buy it if it's priced like an annual.

Heliopsis (not sure of variety - probably summer sun) blooms from June almost to frost
Coreopsis (not sure if this is moonbeam or zagreb)
I also have a yellow echinacea that blooms for quite a long time

Lamium - chequers variety also blooms all summer
My hardy Geranium blooms all summer but i hardly count it because it is so sparse.
Oh wait, you said sun...

If we are counting roses - Golden Showers and Mary Rose both bloom from June until the petals are frozen.