Thanks for the comments. Good to hear that I’ve managed not to be too far wrong about an experience which I have not had myself (though of course the best part is all found object, so I can’t take much credit).
Lorianne – Sounds like a question for Languagehat! But I can think of one or two books that might be able to tell us. I’ll see if I can track it down tomorrow.
The specific name is easy – I can vouch for the fact that there is more than a passing resemblance with the leaves of wormwood and mugwort.