The main "problem" seems to be the boringness of selling at times which is why I think a "bell" would be good. I mean like a bell we can ring to let the shoppers know we are getting ready to close...that way they don't just keep standing there looking making you wonder if they're gonna buy or not. They would then have a small amount of time to either buy a/the plant or leave the nursery. At that point unsold plants can be put on slow mode or new ones potted where the ones were that did sell.
Might also be good to have some funding credit paid back automatically a little at a time as plants are sold. With interest of course.