It's a lovely plant with a pretty tough common name, Swamp Harebell. It's quite rare, growing in wetlands. Margaret Lindgren found a nice patch of them at her home in the Redwoods at The Sea Ranch.
I'm told the flowers are quite small - I have never seen one...yet! A summer bloomer, as you can see, though it can also bloom in early autumn. Its scientific name is Campanula californica. This native wildflower is endemic to the Mendocino, Sonoma and Marin coasts.
Thanks to Margaret for allowing me to share her photo with you here.
Sunny and hot today away from the ocean. Looks like it's foggy to our north at the ocean's edge. Microclimates - the Mendonoma coast specializes in them!