I harvested about 80 kg of potatoes from my garden three months ago and was very chuffed because I would have had enough potatoes to keep my grandson, who is an absolute potato fiend in great organic potatoes for a very long time as well as having a bit over for the rest of the family.  I  very carefully stored the potatoes in plastic drums – one layer of potatoes followed by a layer of hay repeatedly until full. I filled about 5 X 25 liter drums, tightly sealed them and stored them in a cool dry place out of the sun – at the southern side of the house. The unforeseen, by me, has happened and the potatoes which were VERY GOOD for some months have gone sweet. Grandson does not eat sweet potatoes so he has refused my lovely baked offerings for the last few meals and reproached me for planting sweet potatoes instead of the real stuff. Knowing that I did not plant sweet potatoes I decided to read up. Apparently the place where I stored my precious harvest was too cold. Easy mistake to make in Dunedin, especially during the end of winter. Here is a link to the article explaining why cold potatoes become sweet https://indianapublicmedia.org/amomentofscience/cold-potatoes-black-bananas/