Bridewort

Spiraea salicifolia, the bridewort, willow-leaved meadowsweet, spice hardhack, or Aaron's beard, is a species of flowering plant in the family Rosaceae. A shrub, it is native to east-central Europe, Kazakhstan, all of Siberia, the Russian Far East, Mongolia, northern China, Korea, and Japan, and it has been widely introduced to the rest of Europe and to eastern North America. It has been cultivated since the 1500s for hedges and similar applications, but is not particularly well-behaved.