There was a legend that anyone who found a four-leaf clover would become exceptionally lucky, so Muggles often searched through weeds for this "lucky clover."
In Old Felixstowe in southeastern England, there was a botanist who cultivated a special variety of belladonna in his greenhouse. It produced pale purple flowers unlike those of ordinary belladonna. It had once faced extinction because there was always a group of overly enthusiastic people searching for it, only for it to be destroyed in their hands—just as people plucked lucky clovers, held them for a while, played with them, and then threw them away.
The botanist could not stand by and watch such destruction. He picked the fruits of those special belladonnas, protected them, and helped them continue their lineage. As a result, this pale-purple belladonna eventually vanished from Muggle sight, though it still existed in the Wizarding World. The Muggles did not feel much about it. To them, it merely meant one less flower blooming among the weeds.
Besides the special belladonna, he also had stinging nettles of a different variety. Both plants were poisonous, but belladonna was a muscle relaxant. It was precisely for this effect that Spaniards used to drip it into their eyes, making them more alluring.
After belladonna was added to an ordinary wound cleanser, disinfecting wounds did not hurt as much. That meant there was no longer any need to put sleeping draughts in Vera's food as before.
But even without the pain, cleaning wounds produced foul-smelling smoke. There was no ventilation in the dungeons, so Barnaby's detention became this: while cleaning wounds, he had to "maintain good ventilation" so as not to fumigate the Slytherin students and staff next door.
There was also the task of cleaning up Graphorn dung. In short, Barnaby emerged from detention reeking