Y'know, the reason Ralsei gives that "this will probably be [the flowers'] only dark world" is that they're fragile living things which would have to be physically moved. In order to just move them into castle town, you gotta transplant them all the way to the school closet without killing them, and then somehow continue to take care of them inside said closet
Which makes sense but like. I think Raly is underestimating Susie's insanity. She is absolutely going to spend all night online looking up how to safely transplant this species, their care and feeding, bring them to school with Asgore's entire stolen indoor lighting rig, and baffle her entire peer group by starting a school botany club out of nowhere














