My first question is, when the plant is bumped or jostled do the little white things come off the plant in a cloud?

At this stage of life they create those perfect round holes which are actually traps for unsuspecting ground crawling insects.

I don’t know if the cupflower will handle too much hot sun, but since yours have popped back up you are doing something right.

I would not recommend applying any sort of herbicide on the rose of Sharon, since it could too easily affect the oaks.

If you know the direction of the prevailing winds in your area, you might just be able to trace back to the original planting.