As part of its ongoing efforts to promote every single Pokémon out there, The Pokémon Company has shared special content dedicated to Parasect:
Did you know? The bug is mostly dead, with the mushroom on its back having become the main body. If the mushroom comes off, the bug stops moving. Its poisonous spores are also used in traditional medicine. Apparently, spores produced in Alola are not of very good quality.
Source: @Pokemon