Wormwood in Victorian flower language symbolises absence or bitter sorrow. Pairing with Asphodel (a lily which meant 'my regrets follow you to the grave'), a subtle gift for the Potter fans out there.
In magical terms, wormwood can be carried for protection against accidents and for returning harmful magic back to the sender, and was used as an aid in astral projection and visions - although I wouldn't recommend it.
Also the main ingredient in absinthe, along with fennel and anise. Combine in a chartreuse trinket for a little boozy gift.