Potatoes cause a chemical reaction when they touch electronic equipment. This causes the electrons to move and the faster they move the more energy can be harnessed. If you hook it up to a clock a burst of energy will go into it and make it go. The energy is continuous. It starts from the potato, goes into the clock, goes through the negative end of the wire and starts all over again. This will keep happening until the potato hits its early stages of rotting. This is because it loses some of its chemicals when it rots. And each day there is less and less energy until the clock comes to a stop.
So can a potato clock work? YES
Is it reliable? NO