Reference point
Crush a fresh mugwort leaf and smell your palm.
Do this before you read on. An entry only works when you have just smelled the thing.
Bitter, pungent, with a camphor note and a layer of hay behind. Heavier than any other herb in the dictionary.
This entry sits between the green family and the medicinal family, and leans clearly towards medicinal. Bitterness in a smell is rare — very few smells suggest bitterness without being tasted.
Fresh mugwort and the dried mugwort used for moxibustion differ: the dried form has lost its green part and keeps only smoke and hay.
How to smell it
Crush a fresh mugwort leaf and smell it. If you have moxa wool, burn a little and smell the smoke. Two states of the same plant, separated by drying and burning.
Why this one is hard
Because a bitter smell is hard to accept, and many people smell it once and then avoid it.
Scientific note
Mugwort contains thujone, a bicyclic ketone. The same compound is found in wormwood, used for absinthe, and it is why that spirit was once banned in many countries. The amount in mugwort eaten as a vegetable is much lower, but its presence explains the characteristic dry bitterness.
Besides thujone, mugwort oil is rich in 1,8-cineole and camphor — the source of the medicinal and camphor notes you smell even before the bitterness.
In Vietnamese life
In Vietnam mugwort is both a vegetable and a medicinal herb, and in acupuncture it is burned as moxa. The smell of burning mugwort is the characteristic smell of acupuncture rooms and of East Asian traditional medicine.