Is it ok to over water plants in zen garden

Yes. Watering plants give you coins and eventually you need to fertilize them. Once they give you 1,2 or 3 diamonds, they have fully grown and you can sell them for $3000, $8000 or $10000. I don't know if this works with other plants, but if you buy a marigold out of the shop and fully grow it, an hour later they will want to be watered again. Eventually, they will ask for bug spray or a record player. This makes them happy for 1 day and they will give you coins every so often