Herb
The most bitter thing in the garden, and long treated as the most potent.
These are associations the community holds, not settled fact — the more a reading is shared, the bolder it sits.
Nothing in a temperate garden is as bitter as wormwood. The taste is so extreme that the word became a metaphor for the unbearable long before anyone tried to explain the chemistry, and the King James Bible uses it that way repeatedly. Silver-leaved and soft-looking, it was strewn against fleas, laid in chests against moths and steeped into vermifuges, which is where the English name comes from.
Its notoriety is largely absinthe's doing. The nineteenth-century spirit was blamed for madness and degeneracy across France, banned in much of Europe, and eventually more or less exonerated — the thujone content was far lower than the moral panic assumed, and the real culprit was the alcohol. The panic is a better story than the pharmacology and has outlived it.
In practice wormwood is a herb of banishing, of clearing a space thoroughly, and of the darker end of divination. It is often paired with mugwort, its gentler relative, and it is the more serious of the two in every sense.
Readings practitioners have offered, ordered by how many recognise them. Take what serves, leave the rest.
Carried forward
Nicholas Culpeper, The Complete Herbal (1653)
Culpeper declares that "Wormwood is an herb of Mars" and then embarks on the strangest passage in the whole Herbal — pages of astrological reasoning addressed directly to the reader, complete with a running argument about what Mars is doing and why. It is very funny and almost entirely unfollowable.
Carried forward
Common in contemporary practice
Burnt or scattered for banishing and for clearing a space that feels occupied. Practitioners generally treat it as the strong option and reach for mugwort when they want something gentler.
Credit what you carry. Much of this comes from living traditions, and some of it from traditions that are closed — held by particular peoples and not offered for general use. Where you know whose practice a reading came from, name them; where you don't, say that too.