It evolves at level 21.
21
Bellsprout evolves into a Weepinbell at level 21 in Pokemon Crystal.
Bellsprout evolves into Weepinbel at level 21.
evolve from bellsprout
bellsprout and what they evolve into
Bellsprout evolves at level 21.
Level 21
No, you should not raise a Bellsprout at all. Bellsprout is a grass Pokemon, and grass Pokemon (that aren't starter Pokemon) are weak Pokemon. Plus, if you do not evolve him, Bellsprout would be a drag and provides no use other than an HM slave (where you teach a single Pokemon multiple HM moves).
Bellsprout evolves into Weepinbell at level 21. Use leaf stone to evolve Weepinbell.
It evolves into a Weepinbell at level 21.
Bellsprout evolves into Weepinbell at level 21.
let him eat rare candy