Deadheading is not a necessity when it comes to Astilbe Pumila perennials. However, if you do not like the appearance of faded flower stalks, you may want to prune them off once the growing season is over. If you decide to leave the stalks, their dried seedheads will provide additional interest later in the season. Also, note that these perennials should be divided every four years to ensure the maximum blooms. If you do not divide them, they could become overcrowded and not produce many blossoms or get enough air circulation to thrive.