Cannot figure out what is it. Around mid-September. The bottom of Big Cottonwood Canyon, at 1914 m. Any clues?
My first thought was Abutilon, but I couldn't find a match for Utah and looking made me think it was probably something else.
Great! Thank you, Tyrlych and Eric! It is Malvaceae, indeed. Most probably, Iliamna rivularis, which is growing all along this canyon. Here is a summer picture of it: