I don't have a big assortment but of those I have probably Frikart asters and Rozanne ('Gerwat') geranium.

Actually I think my older, bigger ones are 'Jolly Bee' (there is a visible difference, despite what has been claimed. With the now discontinued - as in forced off the market - 'Jolly Bee' being the better of the two).

Deadheading prolongs the bloom season.

Corydalis lutea, indefatigable self sower, in bloom from May till November at least.

Salvia 'Hot Lips' (although may technically be a subshrub :-) Blooms from early spring (March?) until late November....sometimes even into December. Next in line would be Erysimum 'Apricot Twist' or 'Bowle's Mauve'. Geranum Rozanne is pretty high on the list as well.

In Michigan I find Rozanne hard to beat. Gaillardia, Zagreb, and various echinacea are also on the list of my longest-blooming plants. Stella d’Oro has a blank spell for me but I don’t deadhead enough and it was a dry summer.

My longest bloomers are..

Spring:

candytuft

Aubrieta

Creeping Phlox

Centranthus ruber

Summer:

Geranium rozanne (all summer)

Coreopsis moonbeam (going on 9 wks)

Dianthus Carnation (if deadheaded)

Garden phlox

Veronica Royal candles (with great rebloom)

Fall:

Asters

Sedum

hoping for new...Montauk Daisy

gdinieontarioz5

I don't find corydalis lutea to buy here. I ordered the seeds online and sowed them last autumn. Nothing came up. Then I cold-moist stratified the seeds for 6 months in the fridge and sowed them last week. I wish them so much but can't get them established here. :(

Totally agree with your list. Gaillardia 'Goblin' just does not stop. Coreopsis g. 'Sunray' is another but hands down Persicaria polymorpha is my longest bloomer. It starts in May and blooms all summer then in fall the seed heads continue the show.

peren.all

wow, persicaria polymorpha is really stunning. Never heard of it before. Maybe because it's quite a large plant and my garden is small so I grow small persicarias like p. affinis Darjeeling Red and Persicaria vaccinifolia.

Does it tolerate drought? Or it needs consistently moist soil?

It performs beautifully no matter what the weather throws at it. We had an extremely hot dry summer and it laughed it off.

Last year it did not stop raining until the end of July and it performed equally well. Love this plant!

Your zone is so different than mine it surprised me how many plants are happy in both locations.

SeedG, I googled around a bit, and it seems they are hard to sow indoors because of a need for hot and cold stratification. But I have a feeling your zone would be too hot for them. Depending on the source, I found that they handle up to zone 7,8 or 9, but no higher. Also warnings that they won’t grow in the deep south, cannot handle high temps and high humidity, etc. So unless you find them growing in your area, I think this is one you may have to give up on. Sorry.

Here is another two, Roguchi and Betty Corning clematis. Roguchi started in May and is still blooming. Betty Corning started in May and stopped about two weeks ago, BC is my favorite!

Sherry

Funny I've grown many clematis and I've never grown Betty Corning. I'll have to give that one a try. Thanks for the enabling. :)

My hellebores showed color for so long that I lost track - when other stuff started in May, I forgot about them. When I checked this morning, the blooms are gone now. I bet they were colored for six months.

Not strictly a perennial but there are blooms on my neighbour’s large hardy fuchsia almost 10 months of the year.

I’d say one of mine is Astrantia - it continues to get a few fresh blooms after the main bloom in May/June but the dried blooms keep their color and form, and the bees stil get something out of the dried blooms even now.

floral_uk z.8/9 SW UK

Still waiting for my hardy fuchsia to grow. It was planted last year from a cutting made a year before but it's slow to get going. This year it emerged a bit late and it's only 20 cm high. I hope it'll flower next year.

This topic gives me an opportunity to brag about the performance of my wonderful Penstemon, Sour Grapes. And to feel sad that it seems lost to commerce.

it blooms profusely and continuously for me from mid-May to almost mid-December. It has an unusually dark flower color that seems to blend with any other color. Its foliage is a good dark green and it’s stems are an attractive burgundy. Not only that it has a mannerly upright habit which I particularly appreciate as I’m not fond of the Penstemons that have octopus like arms that invade and smother other plants and layer themselves on the ground.

if it has a fault, it is that it seems lost to commerce, perhaps because of confusion about its name as I can find two other Penstemons named Sour Grapes. What a shame as it is way better than the other two Penstemons named Sour Grapes.

Here’s a photo of three of mine. I keep them in a raised bed where I don’t have to worry about losing them to gophers and I can easily propagate them with layering.

I have other long bloomers as follows:

- Gaillardia Mesa Yellow - early spring to frost

- The new Echinaceas, 3 months in summer

- Most Agastache, 3 months in summer

- Most Pelargoniums, mid spring to frost

- Geranium Rozanne, summer to frost

- Many Heleniums, late summer to frost

I don't have one planted in my yard, but other people in my area have rose of sharon and that seems to bloom for ages.

I second rooguchi and Burning Hearts.

A plant which hasn't been mentioned is Tuscan Sun (Heliopsis). Off hand it may well be the longest blooming plant in our garden.

Linum arboreum, iochroma, anisodontea, salvia greggii (I have quite a few of these) - although possibly classed as shrubs or sub shrubs, have proved long blooming and prolific.

Alstroemeria, limonium perezzii, erigeron karvinskianus, scented leaved pelargoniums, penstemon 'Garnet', aster frikartii, glandularia canadensis, papaver miyabeanum.

Corydalis Lutea from yesterday:

Yellow flowers from as early as April and now into November.

Corydalis, absolutely! Nothing comes even close.

Though G. ‘Rozanne’ is no slouch either, but it starts later.

My agastache apricot (something) has been in constant blooms for months and months … in a constant bloom. Even now after a few light frosts over the past month, it still has blooms on it. It’s almost too much. All your other plants go through phases in the season… this guy just starts blooming heavily and doesn’t stop. A few small seedlings have popped up over the past few years too… so I am adding it to other spots.

I haven't seen anyone mention Fernleaf Bleedingheart Dicentra "Luxuriant". This comes up in March in my SW Ontario garden, bloooms in April and continues to bloom enthusiasticly into November. Mine is blooming still under several inches of snow this morning. The official description says it grows in shade to lart shade but my plants haven't read that. They self seed and grow into massive blooming clumps anywhere they please to in my acre garden. They are the ONLY plant that I allow to self seed at will because I love them so much! https://www.gardenia.net/plant/dicentra-Luxuriant

My top two would be Moonbeam Coreopsis and echinacea-any kind as long as it’s in the pink family. For some reason all shades of pink just go and go and go in my garde.

wyndyacre Maybe in Ontario you can have dicentra in full sun, but down here I'm sure it would scorch in full sun. The description depends on the zone. Full sun in Ontario is not the same as full sun in California.

Nevermore44 - 6a I've been searching for this agastache for a long time. Now the nurseries only hold Agastache aurantiaca 'Tango' so probably won't get Apricot Sprite what I believe yours is. Lucky you.

Malva Zebrina. Temps down to 10-12 seems to stop it. Bloomed since very early this year.

Agastache 'Apricot Sprite' is readily available in seed form, here in the UK. See no reason not to assume it is available in US also. Easy to grow from a spring sowing and blooming, iirc, in it's first year.

Oh, it's available!! Often for sale in area nurseries here but later in the season.....not early in the spring when most of the new stock arrives :-) I have even seen it at the box stores on occasion.

If not available in person, High Country Gardens carries Agastache 'Apricot Sprite' so you could do mail order.