also consider planting 2 together ... you can extend flower period that way ... ken

I’ve heard Rogouchi names as one of the longest flowering. It’s got little bell shaped flowers, though, rather than the large showy ones.

I usually have very good luck with many of mine blooming almost continuously if I keep up with deadheading and watering. The first flush is the best, but they will continue to pump out enough flowers to keep me happy. :) Pink Chiffon (aka Hagley Hybrid) has been one of the most reliable in that regard. Fairy Dust (a sport of Venosa Violacea) blooms nicely for a very long period, as well.

jackmanii at a local zoo bloomed heavily for months.

Also what Ken said. Planting multiple varieties, especially if they are in different clematis groups, can help extend bloom time dramatically.

Planting two different pruning groups together can increase the bloom period but it also greatly increases the difficulty with pruning. And if you can't easily prune an individual vine according to its group guidelines, you run a high risk of altering that vine's bloom cycle. So it might work OK the first season but fail in extending the bloom period in subsequent years

Very few clems have a long bloom season. The pruning group 2's will often have a rebloom or a second flush later in the season but rarely - as in almost never - flower all summer. And deadheading won't help with that :-)

Jackmanii is known to have a long and almost continuous bloom through summer (July, August and September). And 'Arabella', which is a hybrid between a vining clem and a herbaceous one, has been acknowledged as the longest blooming cultivar (June through to October) but is a sprawler, not a vining plant, and best used to scramble through other plants, as a groundcover or to drape over a wall.

Good point re pruning Gardengal...

Gardengal, I hadn’t considered the pruning. That’s a very good point. Perhaps if they were planted near each other but not ON each other, a similar effect could be had without the pruning troubles.

and I guess I don’t know if the deadheading helps or not! I assumed it did, but perhaps they would flower just as long if I didn’t deadhead. I should do a trial sometime with the same variety side by side... Hehe. Perhaps you have just cut down a chore for me :)

Some of my clems do usually bloom all summer, but not in copious amounts. Just enough to look pretty. :) With flowers that large and showy, it doesn’t take many. And they certainly do not continue to show off if I don’t water them enough. I suppose whether or not you get continued repeat is very dependent on variety and location.

I’ve seen Arabella receive very high praise on this forum! She sounds like a winner.