[GordonS]

Do you have a source that the 9sqm claim? It seems... completely unbelievable.

My wife's parents grow various vegetables in an area of that size, and there is no way it could provide all their vegetable needs.

[cma]

If you grew potatoes you’d get 15000-45000 calories out of 9 sq meters. Not enough. 9mX9m (81sqm) and at the high end of yield you could get above starvation.

[GordonS]

At least in the UK, I thought you could only harvest potatoes once a year? There is a 2-week school holiday in October, which in some parts of Scotland are still referred to as the "tattie holidays", because that's when the potatoes are harvested (I did it as a kid, it was back-breaking work...).