noun
meadowsweet (Filipendula multijuga)
A flowering plant native to Japan, often found in mountainous areas. The name is also used for other Filipendula species.
夏になると、山でしもつけ草が咲いているのを見かけます。
In summer, you can see meadowsweet blooming in the mountains.
The name しもつけそう is said to derive from 下野 (Shimotsuke, an old province corresponding to modern Tochigi Prefecture) where the plant was first discovered, combined with 草 (grass/herb).