So i plant melons, do I ever need to re-plant them? Do they regrow when harvest by a settler? What if I harvest them myself?

I have another question -- When I planted crops for the Sanctuary folks, I didn't find all different kinds of plants. Can I keep adding new plants or is my farmer going to be overwhelmed eventually?

Farmers can only work on 6 crops, so after 6 u need to put another one.