As of the 4th generation, Tropius cannot evolve.
it doesnt evlove by level. you need to trade it and it will evlove for them, then they trade it back.
No pokemon evolves into tropius nor does tropius evolves into any pokemon.Hope it is helpful.
Level 28.
Level 36.
Level 25.
55
Level 20.
level 33
level 40
Level 18
Magikarp evolve at level 20.
leaf stone