What you are seeing are the fruits of the potato. They look just like green tomatoes but are poisonous, put them in your wheelie bin not your compost.

i have had what you discribe on several potatoes ,but these really look like tiny red potatoes moon grower

I promise you Dab these are the potato fruits and poisonous as are the fruits of most solanums.

Seed potatoes are not the fruits. Seed potatoes are grown in areas where there is little or no blight and are carefully checked a 'rouged' to remove any that are not 100%. One of the main reasons for not saving your own potatoes to use as seed the following year is the risk of blight.

Copy and paste this link to your web browser...

http://commons.wikimedia.org/wiki/File:Potato_fruits.jpg

okay moon grower .thanks very much. :)

There have been reports this year of plants developing tiny potato like growths on the stems and these are not the fruit. Cut one open, if it is a fruit then it will have seeds inside, if it is an embryo potato then it will not. It could be a reaction to the odd weather. Remember that tubers grow from roots produced from the stems of the plants, usually underground, but I have seen them form on the above ground stems before. The spuds are useless though as they never properly develop and soon turn green.

That is interesting Owdb. have not heard of until now and certainly haven't seen.

Only seen it once in 40 years and that was on a shoot which was lying on the ground rather than upright.

Ah!