Swiss chard is pretty tough, but will only do you for the occasional meal.

Again, if you have cover (cold greenhouse) there are a lot of winter salad crops available, but the main problem is that everything grows so slowly at that time of year, so in practice it doesn't work very well. Not in Yorkshire, anyway.

Jerusalem artichokes can be left in the soil a long time without coming to harm - again, there's a limit as to how many you can eat!

My Jan-March eating from the garden is mainly apples stored since November, and after that we hit the frozen fruit - mulberries and strawberries - and the medlar jelly. Hardly staples! But if I didn't have so much shade from the fruit trees (not to mention next doors grove of mature birches, the other next door's lime, and my own cherries and hollies) I would be able to grow more beans and add them to the deepfreeze.