Bulbasaur, Sunkern, Shroomish and Breloom learns both Seed Bomb and Leech Seed by leveling up.
Exeggcute learns Leech Seed by leveling up and Exeggcutor learns Seed Bomb By leveling up.
To get a Ferrothorn with Seed Bomb and Leech Seed, get a male pokemon that knows Seed Bomb and Leech Seed that is capable of breeding with ferrothorn (listed above) and get a Female Ferrothorn and put them in the day care.
Also check out Ferrothorn egg moves page and the Breeding page.
Those might help.