Wiktionary
seed potato
n. A potato, usually with tiny shoots (chits), which is planted in the ground in order to grow a potato plant.
Usage examples of "seed potato".
Soon there won't be a seed potato available that isn't allegedly loaded with antidotes to everything from the common cold to the black death.
Gently laying it upon his palm he smoothed away the dark earth which clung to it, exposing to his horror the familiar outlines of a common seed potato.
The same sort of noise a gardener might make over a seed potato that had a bit of blight on it.