The flowers are like little pincushions, beautifully symmetrical spheres-dense clusters with protruding pistils. They like water, they like shade. The Ladybird Johnson Wildflower Center calls them honey plants---I hadn't heard that term before, but according to the interweb a honey plant is one used by honey bees to make honey---makes sense. I guess the implication is that they don't use the nectar from all flowers to make honey.
This is a great shrub to plant in your garden--they have interesting blooms, are native, attract a variety of pollinating insects, birds and bats, are easy to grow (mine has survived a bit of neglect) and will do well in a variety of soil types--not just waterlogged wetlands.