Ian B wrote:
Do very small "seed" potatoes (the little blighters missed when I dug up
last year's crop, basically) just have insufficient capacity to produce a
full plant? I would have thought once they get going, they'd root and the
size of the seed potato wouldn't matter, in my amateurish ignorance.

I have had giant potato plants grow from peelings! But could it be to do
with the nutrient levels left in the soil, perhaps? If you grew potatoes
there last year and didn't feed for potatoes this year, perhaps they didn't
have enough oomph in them to get any further.

I have a small field of potatoes growing under my beans. :-/