Pick up a few OSP this summer and plant them in a good-sized pot or in your flower beds and you will be rewarded at the end of summer with actual potatoes. Right around the first frost or when you do your fall clean up, pull up your plants and harvest all the potatoes, no matter how small. Clean them off and store in a warm area. I use brown paper bags or wrap them in newspaper and put them in a cardboard shoebox, then store them in the house where temps don't drop to freezing. I have found that only the black or lime-green plants will grow true. The tri-colored plants will not produce true to the mother plant.
In February, get them out and discard any potatoes that are not firm. If you live in a warmer area than my Zone 6, you may want to start yours earlier. Lay them in a shallow dish and pour water into the dish until approximately half the potato is covered. The area of the potato that is underwater will grow roots and the top half will grow slips. It will take a couple of weeks until you start to see the roots grow and then until the slips start to grow, but once they start they will grow very quickly.
I let my slips grow to 3 to 4 inches long before I gently wiggle them loose from the potato and place them in a glass of water to root. Your potato will continue to make more slips. When the roots develop, I move them into pots to finish. It took me approximately 4 weeks from start to getting them into their pots. Right now I have 3 of my 5 potatoes producing slips and I have 17 slips from those 3 potatoes, and they should produce more.
Over the years I have found that not all plants will produce potatoes and not all potatoes will produce slips. OSP are bred for their beauty, not for the production of potatoes. These 5 potatoes came from 3 plants that I grew last year.