The valerian flowers (Valeriana officinalis) were attracting several hoverflies. In the past it was used for its calming effects and to help sleep.  Apparently medieval Swedish bridegrooms kept some ground up roots in a sachet to ward off jealous elves and sachets would protect a house from evil and lightning!  One story also tells that the Pied Piper of Hamelin used it to draw the rats away from the city.