I could be wrong, but there is no definitive large scale charge. Meaning it's used solely as the adjective large and there are no specific legal ties to it. So it's not like 100 plants = large and 10 = small, it's like if you get busted with ten you will be charged with 100 you charges will obviously be a lot larger than if you got busted with ten, the more weed, the more charge. The difference is when it gets reported on the news 100 plants will get reported as large scale, and ten most likely as small or personal. It's all just a matter of personal opionion and the social status regarding weed in your area i guess. I could be wrong completely.