Just a quick update. I finally got around to Googling to identify the prolific yellow flower that’s been a star in my main garden for the past few years. See the image below for the Coreopsis Moonbeam or maybe Zagreb. With a big patch of them, as in my case, the yellow blossoms are so intense in combination with the green stalks and frilly leaves, not really leaves, that the foliage momentarily can appear to be blue (yellow and green make blue, right?) in bright sun.
Web photo courtesy of coreopsis.info