I'm going to take a chance here and assume, for the time being, that Epilobium latifolium (now Chamerion latifolium) is still a valid one to kick off this forum... ? (Since "Zauchneria" [lately renamed as Epilobium] is listed here as such, I think I'm on solid footing (?), but if not, moderators, please feel free to move or nuke this posting! :))
Arctic fireweed, or river beauty, occurs here over a wide elevation range from montane gravel bars (photo #1) to the high alpine (photos 2-5, where a hint of purple in the scree gradually resolves itself into bands of bloom, as one approaches) - wherever there is ample moisture, at surface, or running beneath the scree. It is a pleasure to see, whether up high or in less lofty areas.
I have just read that the species has a distribution that seems rather curious - though described as "essentially circumpolar and circumboreal", it is said to be absent from most of Europe, but present through the Himalayas and other Asian ranges:
It seems remarkable that the same subspecies occurs in the mountains of Pakistan as is said to occur here (ssp. latifolium)!