Herb
The poor man's treacle — pungent, unglamorous, and trusted everywhere it grows.
These are associations the community holds, not settled fact — the more a reading is shared, the bolder it sits.
Garlic is one of the oldest cultivated plants on earth and has never had a quiet reputation. It was rationed to the labourers who built the pyramids, sworn by in Greek oaths, banned from certain temples for the smell, and issued to soldiers in more than one army in the belief that it kept wounds clean. Every one of those uses is documented; none of them tells us whether it worked.
Its protective reputation is nearly universal across Europe and western Asia, and long predates the vampire, which is a nineteenth-century literary arrival attaching itself to a much older idea. Garlic was hung in doorways, plaited into ropes over the hearth, and worn against the evil eye from Spain to the Caucasus.
Craft keeps all of that: garlic for protection, for banishing, for guarding a threshold or a sickroom. It is also, unusually among protective plants, entirely edible and entirely ordinary, which practitioners tend to like. A working that ends with dinner is a working most people will actually do.
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 gives garlic to Mars and repeats the old name for it, the poor man's treacle — treacle here meaning an antidote rather than syrup. He then adds his own warning that its heat is vehement and sends ill vapours to the brain, which is as close to moderation as he gets.
Carried forward
European and west Asian folk practice
Hung at doors, plaited over hearths and worn against the evil eye across an enormous geographical range. The vampire association is late and literary; the protective use it attached itself to is very much older.
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.