I don’t know what this plant is but an assortment of butterflies and other insects were attracted to the puffy blooms.
The tufts from the flower heads made me think of thistle but the rest of the plant did not, with no sharp spines in sight.
This little yellow one was the smallest flying insect I saw. The bloom he picked had more of a purple tinge than the others, prettier or tastier perhaps.
The butterflies were all doing the same reaching into the tops of the flowers so they must have been getting something.
This patch was two to three feet deep (0.5 – 1 meter) and ran along the edge of a pond. I could not see over the top from the mowed lawn where I was standing; I resisted getting closer due to the potential for alligators to be hidden in the greenery.