well i have a meganium with leaf storm, first you have to catch a male sceptile,exeggutor or torterra and a female meganium, train sceptile,exeggutor or torterra till it knows the move leaf storm then put it in a pokemon day-care with the female meganium, then come back for awhile when you get a egg, hatch it it will contain either a male or female chikorita that knows leaf storm
hopes this helped
(note:sceptile,exeggutor and torterra can learn leaf storm via level increase)