After they have ran out of room in the one or 3 gallon pot. I would not go from a cup to a 5 gallon container. Why water all that soil to reach the tiny roots in the center?I wouldn't want to burn em I figure ill transfer them soon I have this other soil its called MG potting mix with moisture control ? It says it feeds plants up to 6 months on that bag I was just wondering for the future. When should I move them into a 5 gallon pot ?