Oh, I think every summer here is plenty hot. This one was somewhat cooler and rainier than the last, at least according to my increasingly vague memories LOL. Seems to me establishment caused a definite physiological change to occur.

I have referenced that website many a time, in fact it's what helped me select 'Ledon'.

I have never detected any particular aroma from cistus foliage :-) And there are plenty of them planted around here and of all different varieties and most in very open, sunny and heated positions.

Of all the cistus species and cistus-like plants, my favorite is xHalimiocistus 'Merrist Wood Cream'. I find that it tolerates our usually wet winters much better than cistus and will also thrive in a less open position.

I've only ever smelled them in the Mediterranean region. I don't recall ever being aware of the scent here in the UK although they are quite widely grown.

Interesting, so they are fragrant in warm summers areas...I should ask the Cistus man himself - he named his nursery after them - what they do in Portland. Since that is a little warmer than both of you. If so, curious, I cannot think of another plant with such a feature. It isn't as though lavender 'Grosso' smells in Delaware and not in Seattle, or vice versa.

'Merrist Wood Cream' I have in a more sheltered spot because I figured it was a little less hardy. No fragrance on that one here, after several years.

Lots of plants share this feature in my experience. Box, lavender, Rosemary, in fact all those aromatic herbs smell far stronger in their natural environment than they do here. Box especially is noticeably much smellier in hotter climates. It's barely perceptible in my garden apart from a couple of hot days in high summer.

'Merrist Wood Cream' is short-lived in Zone 8.

well, smelling stronger, yes I can grant that. But this was a total change in foliage too. It was not sticky at all last year. I know because I was picking a leaf once in a while to see if there was any fragrance. It's as though there was some differential gene expression going on. The way Osmanthus changes from pointy leaves to smooth ones or equivalent. Fragrance is volatile organic* chemicals so yes it will be noticeable for certain plants when the air is humid and warm. But again, it isn't as though rosemary picked from a garden in Northumberland wouldn't work for cooking because it lacks fragrance!

Embo, Helianthemums are short-lived here unless they have a very dry spot with open (relatively, anyhow) soil. Additionally some cultivars have done better than others. The orange ones oddly appear more tolerant of my climate...could just be chance though. I've definitely lost over 50% of the ones I've tried in 10 years. My 'Merrist Wood Cream' is in the driest spot I can find on a south facing wall, and survived the 2nd polar vortex winter. (the spot that opened up because Ceanothus 'Concha' was killed by the first! As expected for a Mediterranean plant versus a coastal CA plant, it seems somewhat more tolerant of aerial humidity)

* (in the original chemical sense of course, not the agricultural one)

"'Merrist Wood Cream' is short-lived in Zone 8."

That has not been my experience. It is just as long lived as any cistus in my area, provided it is given very well-drained soil.

Yes, the leaves do indeed give off a wonderful sticky substance that has been used in religious ceremonies as well as healing for thousands of years. Shepherds ran their sheep through the fields and then combed the substance off the wool and sold the blocks of gum in the markets where it can still be found in some Middle Eastern markets. If interested the following link will give more details. Cistus was a favorite in my Walnut Creek, CA garden - true Mediterranean climate - and we grew many different types. When happy they thrive on total neglect!

http://portugalresident.com/cistus-the-queen-of-the-algarve