Looks like button bush to me also. Easy to spread. get some rooting hormone and take cuttings in the spring. poke them in the hormone then poke them in the ground.
I started a shrub screen before I moved to miscanthus. I used a variety of shrubs including button bush. The button bush is still thriving. I'm almost worried it may shade out my grass someday.
I've mowed it, disked it, sprayed it with gly, liberty and atrazine and those things are still growing...