and which plants yield the least ?
i would nominate this
it's informal name is Walking Stick Cabbage. it grows like one of those "fig plants", you know, the decorative indoor plant that is pretty common.
WS cabbage grows about 6 feet tall. the leaves are thick. my experience is that one plant will occupy 4 square feet in a garden and yield one "hungry adult size" serving every other day, which is about 2 leaves, during the spring & summer.
so that's about 5 to 10% of your diet, from 4 square feet.
this is a baby.
on the other end of the yield scale, i would nominate Miner's lettuce. it tastes good but you can pick a gallon, and by the time you cook it, you get 4 mouthfuls.
in the middle, in terms of yield, i would put cherry tomatoes. i had about 50 square feet last summer and that yielded about 50 pounds.

