What it the fragrant, but moderately toxic compound in this plant?
I will post the answer in one week.
Answer: The plant is Galium Odoratum, or Sweetscented Bedstraw, German name is „Waldmeister“. It contains the active compound Coumarin (German: Kumarin), which gives not only this plant but some cinnamon varieties and also hay its characteristic smell. The plant is used as ingredient of May Wine (German: Maibowle). It is advisable to limit the quantity and to use only plants before flourishing, otherwise the too high coumarin concentration can cause head ache.