Though i'd put this one here as it's not really black magic but often fell under witchcraft, shamanism, or even ceremonial type magics.
So people go on and on about using this or that herb to heal, induce trance work, etc. Yet seldom do you actually hear of them speaking about or actually discussing how the plants were or are used to combat spirits, demons, angels or even gods / goddesses. Figure almost all oral and written lore talks about how the plants of this world can be used to destroy the physical form of non-worldly beings.
Perhaps the most well known example being from Nordic lore and the story of Mistletoe and the death of Baldur. A number of Native American stories speak of for everything that exists there is a plant that will cure it, or destroy it if is is not native to this world. If one expands upon the Baldur story then you could infer that the Aesir & Vanir also believe that their are plants upon Midguard that can kill them or destroy the earthly form.
Some early stories of Christianity infer that the Dogwood with it's blood stains upon the petal can destroy any demonic entity due to the blood of Christ infusing it's petal. Sort of a payment to the fact Jesus was crucified upon a dogwood and it would never again grow large enough to crucify a man upon per some lore. An arrow or shaft formed from the branch of a dogwood seen as a holy and blessed shaft. If coated or soaked in the oil of the flower making it even more potent. Lethal against demonic forces based under Christian concepts.
Some lore claims the American Hemlock tree can kill demonic entities or evil beings through deception. The tree gains it's name due to the fact the crushed needles have the same smell as the poisonous plant. So a shaft made from a branch from the tree and bathed in the crushed needles would deceive the target. It would believe it has been poisoned by the real plant.
Roses have a dark usage as protectors who grab and tear at both ghostly trespassers and witches. So they'd be planted around homes, especially near doors and windows to protect ones family. Can't recall the specifics now but red wasn't always for love, sometimes it used to hide blood. After all the rose belonged to the woman of the house and was her's to command.
But just a though regarding herbs, plants and such they weren't always about healing or things like that.
So what do you (collective) think?