The early routes.
I don't really think you can. The thing is, in Sapphire you can catch Lotad but not Seedot and in Ruby you can catch Seedot but not Lotad. However in Emerald, you can catch both. So You'd have to trade from a Sapphire or Emerald. Lotad can be found on route 114 on Pokemon RUBY!
you migrate lotad from Pokemon emerald and ruby, and migrate it in pal park.
The early routes.
where to catch lotad in Pokemon platinum i really need one to complete the national dex
yes on route 102
route 102
lotad is on a edge near the jumping carvanha
After obtaining the national Pokedex insert Pokemon Emerald/Ruby/Sapphire into your DS then you can find it on route 203 & 204
You breed a ludicolo with a pokemon that knows razor leaf.
Pal Park one.
You can catch a Lotad/Lombre shortly before the first gym (Roxanne.) Lombre can learn Flash, but I'm not sure about Lotad. Lotad evolves into Lombre.
Go to White Forest and Lotad will pop up some time Good Luck!:)