Don't do drugs kids. Crack is whack.
Minerva McGonagall was the first to notice something was happening to the students of Hogwarts. It started in her house after all. While serving as deputy headmistress she was observant and experienced enough to realize her classes seemed a touch too happy to sit and listen to her lectures, the student table was a might too ravaged and ransacked from the preceding meal, and the loitering around the second floor statue of Gregor the Gregarious or fourth greenhouse little too nonchalant. Curiosity (and professional dictation of course) getting the better of her after one suspiciously placid class of fourth year Gryffindors and Slytherins, she made her way down to the greenhouses to 'catch up' with her dear friend Pomona. If she happened to snoop a bit, well, no one would begrudge her job as a head of house.
It seemed her disciplinary intervention would be needed when she rounded the corner of greenhouse four to see one of her more ridicule prone lions surrounded by upperclassmen. Neville Longbottom, it would seem, had managed to find trouble once again. So, when the normally foolish and clumsy boy started expertly and confidently assigning packets with names to what could only be couriers, succinctly ordering them away before moving to the next, Minerva couldn't help but feel a little happiness at his newly discovered confidence. The couriers dispatched, Neville sat back, pulled another packet out, decked up what Minerva recognized as sweet leaf, and promptly fell ass over teakettle when he spotted her presence. The sudden regression of confident young man to blunder-bumble made Minerva flinch and rethink any thoughts of punishment. She felt no small amount of pride watching her students grow and mature into adults, Neville had certainly found his niche with his newest business venture, and anyway, he had sweet leaf. Heaven knows her Gryffindor's could give her a migraine.
Pomona Sprout was all too aware of her student's ambivalence towards Herbology. She didn't begrudge them, after all, it wasn't a particularly sexy topic. Hands on work, kneeling in dirt, and composting dragon dung all day was hardly the first thing that came to mind when 'Wizardry' was mentioned. Still, it would be nice that her students showed some interest in the subject. It came as a relief and pleasant surprise when young, bright-eyed, Neville Longbottom showed not only interest, but aptitude for the discipline. He quickly displayed an enthusiasm towards independent research and soon Pomona found in him the protégé she had heretofore only dreamed of. It was only fitting then that she allocate a section of the fourth greenhouse to his continuing study of Herbology.
When Neville started experimenting with mushrooms and other plants of objectionable legality, Pomona was worried she would loose her star pupil. When Neville started bringing in plants she knew she didn't grow in her greenhouses, Pomona became frightened. There was no way Neville would be able to afford Dragons Wort on a student's stipend. Any doubts Pomona had that her prized student had set up shop in greenhouse four flew out the window like a barn owl the second her student approached her to 'hypothetically' ask market prices. No protégé of hers was going to sell inferior product, get caught, and subsequently kicked out, she had seen it happen before with her husband. Pomona would make a master herbologist out of Neville, and if quality checking was what it would take, that was a mantle she was only to willing to take up. Anyway, Neville had managed to get his hands on Green-Grent Mushrooms; her favorite.
Severus Snape was a busy man. It didn't mean he was blind. He had noticed a dramatic learning curve in a certain bungling student as of late and if there was one thing he disliked, it was not meeting his personal quota of students-snarked-at. When he caught Greyson Fields, one of his few competent students, switch cauldrons with Longbottom out of the corner of his eye he knew something was up. The students were looking out for Neville at the risk of his displeasure. He gathered through opportunistic eavesdropping that Neville had all but forgone the mantle of the ridiculed. Among the Hufflepuff's he was mentioned with a touch reverence. There was intrigue at play in Hogwarts, luckily Severus had the tools to get to the bottom of his adopted mystery.
Legilimency had its perks and Severus wasn't above snooping in the minds of his students if it meant solving a puzzle he had never predicted. It seemed that Longbottom had set himself up as Kingpin of Hogwarts and was endearing himself to students and teachers alike with his wares. Severus couldn't help but be surprised by the cunning Neville had used to set up his trade. Still he supposed the downright stupidity, ergo bravery, of running a cartel in a school (of all places!) made the boy more a Gryffindor than before. Severus mused that the boy could be used to his benefit, depending on his stock, he was a busy man after all. Speeding up the everyday schedule could only result in good things for him. So, when midterms or finals rolled around, it wasn't suprising to catch Snape heading off to the fourth greenhouse. He had the fastest turn around time of graded exams in Hogwarts and if he abused a few beans to keep it that way, well it was between him and a certain student.
Filius Flitwick was always a touch on the whimsical. He couldn't help it, it was the charms instructor in him, always looking for the charming in the world. If the charming happened to present itself to him through an opium-tinted haze, well, every character had their flaw. Unfortunately his flaw had flaws of its own, mainly the accursed distance between his quarters in Hogwarts and his dealer who lived behind a Muggle chips shack in Aberdeen. While Filius accepted his flaws, he also played to his strengths. He kept his ears close to the ground; metaphorically and literally. It was a point of pride of his that he was both a professor and friend to his students, if any of the faculty was attuned to the young witches and wizards in Hogwarts, Filius liked to think it was him. A great surprise then, transpired when he found he was one of the last to hear about the new business venture of one of his most forgettable students: one Neville Longbottom.
The rumor mill spun tales of the 'apothecary' Longbottom ran behind greenhouse four (and on Thursdays behind the second floor statue of Gregor the Gregarious). If the students, and some of his esteemed colleagues were to be believed the quality, breadth, and prices of Neville's venture was first rate. Seeing as the second floor statue was a might closer than Aberdeen, when Thursday came around you can be sure Filius took his old bones to visit Gregor the Gregarious and burn the 'midnight oil' so to speak. Nowadays Filius Flitwick is more whimsical than not. When the weekends roll around he is rarely seen without his dream stick.
If you were looking for something recreational, Neville Longbottom was your man. He was Hogwarts best kept secret. So, naturally, the whole school knew.