No you can't the only way is to use AR (Action Replay), trading or pal parking.
route 222 with poke radar
level it up...
Simple. You just battle Candice.
There is no way to get Bulbasaur in Platinum without trading or Pal Parking.
no you can't
Nowhere.
you can trade something for a venusaur and catch a ditto ,put then in the daycare , and that sould give you a bulbasuar
You can fiind a bulbasaur at route 222 in the grass with a pokeradar.
you go to the survival zone
May got her Bulbasuar in "Grass Hysteria!"
if you have heartgold you can get one by beating all 16 gym leaders and beat both final fours then you get to choose between bulbasuar charmander or squirtle
you can't catch him in platinum but in soulsilver or heartgold you can catch him then trade it to platinum.