What are seed potatoes? Seed potatoes are not actually seeds at all. Instead, they are simply potato tubers that are used for planting. Most often, they are saved from last year's harvest and stored over the winter under strict conditions to keep them firm and disease free.

Use seed potatoes and buy them online or from garden centre. If not use organic potatoes from the supermarket because they are not treated with pesticides. I have used ordinary potatoes from the supermarket and still got a crop of potatoes but maybe they were a bit smaller than if I had bought seed potatoes.

https://www.suttons.co.uk/potatoes-onions-garlic/potatoes

My own effort at growing potatoes in pots, first time I did it.