It's a long time since I did this, and my memory may be faulty, but I'm sure I remember putting money trees in a Sim's inventory to move them. I'm talking about plants that were in the garden, not in pots (it was before there were plant pots in the game). Possibly other plants as well as the money trees, I honestly don't remember. It seems to me that the plants lost their perfect quality when they were replanted, but they did survive. Have you tried moving the plants into your Sim's inventory? As I say, it was a long time ago and successive patches or EPs may have changed things, but I'm sure I remember doing it.