Project Potato: Step by step guide to growing a potato from an adult potato spud

Purpose
The purpose of this project is to demonstrate how to grow a potato plant from a mature, adult potato (such as what you may buy at the grocery store).

Introduction
If you've gotten a potato from the store you've probably noticed that little arms, or spuds, will begin to grow out of it. As it turns out, each one of those arms can grow into a potato plant. But there are a lot of questions that come up about actually growing a potato plant from one of those arms. Below are my observations with growing a potato plant from an adult potato.

One adult potato can grow several arms. I actually set an adult potato on a wet sponge (kept wet about twice per week) on a window sill that received daily sunlight to provide a source of water for the potato. Once one of the arms was approximately 1/2 inch tall, I sliced off the end of the potato with the arm (you can see the remains of the end of the potato in the picture below). Then approximately 1 inch of soil was placed in the bottom of a 12 x 12 inch well-drained plastic pot. The potato end with the arm was placed on top of that soil followed by more soil so that the potato end was covered leaving only the arm above the added soil. Following that, the pot was placed into direct sunlight (to receive around 8 hours of daily sunlight).

For the first few weeks (this is in early Spring), 20 ounces of water was provided to the pot, once per week. As the arm grew upwards, additional soil was added so that no more than 1 inch of the potato plant stem was visible. Once the pot was full of soil, the volume of water added once per week was increased to 42 ounces.

After two months, curiosity got the best of me so I carefully removed the potato plant from the pot so I could observe what had been going on in the soil. As you can see from the photo, a collection of 3 potatoes had been developing. As well, the root system came out from the original arm (or spud). This was somewhat of a surprise for myself as I expected that the potato end I had sliced off the original potato would have grown roots...which was not the case. In any case, it appears that the set of potatoes would not reach appreciable "adult" size until four months (120 days) have passed.

SUMMARY	(Enlarge)	[1] Planting of the potato end holding the arm (or spud) approximately 1/2 inch in length. [2] Photo of the potato plant at the point when the pot was full of soil. [3] Photo of the potato plant at approximately 2 months. [4] Photo of the potato plant extracted from the soil revealing where additional potatoes were being created from as well as the root system.
EXTRACTION	(Enlarge)	After careful extraction of the potato plant, this photo illustrates the growth of three new potatoes and the development of the root system.
ZOOM	(Enlarge)	Zoom of the region where the new potatoes are growing from. The yellow outline indicates the end of the original potato (which the arm or "spud" was growing out of) that was cut off and placed into the soil.